Automotive Technology Department

Automotive Mechanics
Level-II

Module Title: - Servicing Engine and associated System Assemblies

 1. Unit one: Overview of engine and associated systems

This unit will also assist you to attain the learning outcomes stated in the
cover page. Specifically, upon completion of this learning guide, you will be
able to:

 Overviewing of engine and associated systems

 Identify types of accessory drives related Components
 Identify types and application of gaskets and sealants
 Identify parts registration/identification number
 Preparing service work activity plan
 OHS and Hazard identification
 1.1 Overview of engine and associated systems
An Engine is a mechanical machine used to convert the chemical
energy of the fuel into heat energy and then to mechanical energy. It
is usually called a Heat Engine.

Basically there are two types of heat engines external and internal
combustion engines.

a) In an external combustion engines combustion (burning of a fuel)

is taking place outside of the Engine. Eg. Steam engines
b) In an internal combustion (IC) engines combustion is taking place
within the engine itself. Eg. Spark Ignition (SI) engines
Figure 1‑1 Engine classification
 1.2 Engine mechanism and exterior parts

a) Crank gear mechanism: - which includes the crank shaft,

connecting rod, piston and cylinder.

b) Valve gear mechanism: - which includes the camshaft, valve

lifter, push rod, rocker arm and shaft, valve spring, intake and
exhaust valves.
1.3 Engine systems

A. The starting system; - which includes the battery, start/ignition

switch, starter motor.
B. The intake system: - which includes the air filter, carburetor,
intake manifold.
C. The fuel system: - which includes the fuel tank, fuel line, fuel filter, fuel
pump and carburetor.
D. The ignition system: - which includes the battery, start/ignition switch,
ballast resistor, ignition coil, distributor, HT cable and spark plug.
E. The lubricating system: - which includes the oil pan, strainer, oil pump, oil
line, oil filter.

F. The exhaust system: - which includes the exhaust manifold, exhaust pipe,
catalytic converter, muffler, tail pipe.

G. The charging system; - which includes the battery, start/ignition switch,

regulator, alternator.
H. The cooling system: - which include the radiator, lower hose, water pump,
water jacket, thermostat, Upper hose, and cooling fan.
 1.4 Types of accessory drives related Components

A.Water pumps
• The burning of fuel in an internal combustion engine produces heat, which is
sufficient to melt the metal of the cylinder.
• It is the function of the cooling system to prevent the engine overheating but it
must also allow it to operate at a temperature high enough to assist in effective
combustion.
• If the engine operating temperature were allowed to go unchecked, it would
burn and dry up the lubricating oil film, so that the pistons would seize in their
cylinders and distortion would result from over-expansion of metals.

Figure 1‑2 Water pumps

 B. Alternators
• In the charging system electronics devices such as diodes for
rectification of current in alternator zanier diode and transistor
for circuit opening and closing in transistorized regulators are
use.
• In this unit, the construction and function of diodes and
transistor, the purpose of the charging system, the component
parts of alternators, the generating principles of alternator, the
charging system service and repair are thoroughly discussed.

Figure 1‑3 Alternators

 C. AC compressors
• The compressor is the power unit of the air-conditioning system
that puts the refrigerant under high pressure before it pumps it
into the condenser, where it changes from a gas to a liquid.
• A fully functioning compressor is necessary for the air-
conditioning system to provide peak performance.

Figure 1‑4 AC compressors

 D. Power steering pumps
• The power-steering unit is designed to reduce the amount of effort
required to turn the steering wheel.
• It also reduces driver fatigue on long drives and makes it easier to
steer the vehicle at slow road speeds, particularly during parking.
• Power steering can be broken down into two design arrangements:
conventional and nonconventional or electronically controlled.
• In the conventional arrangement, hydraulic power is used to assist
the driver.

Figure 1‑5 Power steering pumps

 E. Supercharger

• A supercharger is an air compressor that increases the pressure or

density of air supplied to an internal combustion engine.
• This gives each intake cycle of the engine more oxygen, letting it
burn more fuel and do more work, thus increasing the power
output.

Figure 1‑6 Supercharger

 1.5 Types and application of gaskets and sealants
o Gaskets seal a connection between two components or flanges that have flat
surfaces, while seals are used between engine parts, pumps, and shafts that rotate.
o Gaskets are used wherever a union or flange is required to prevent leaking.
o Gasket made of fiber materials, rubber, neoprene (synthetic rubber), cork, treated
paper, or thin steel.
o When parts are fastened together, the gasket material fills small gaps, dents, or
scratches in the mating surfaces.

Figure 1‑7 Gaskets

Gasket Rules
1. Inspect for leaks before disassembly
2. Be careful not to damage mating surfaces while removing parts
3. Clean off old gaskets carefully
4. Wash and dry parts thoroughly
5. Use a sealer if specified
6. When assembling, start all bolts by hand
7. Tighten fasteners in steps
8. Use a crisscross tightening pattern
9. Do not over tighten fasteners
10. Apply only the specified torque
 1.6 Parts registration/identification number
A. VIN number
Before any service is done to a vehicle, it is important for you to know exactly
what type of vehicle you are working on. The best way to do this is to refer to
the vehicle’s identification

Figure 1‑10 VIN location

number (VIN). The VIN is given on a plate behind the lower corner of the driver’s
side of the windshield as well as other locations on the vehicle. The VIN is made
up of seventeen characters and contains all pertinent information about the vehicle.
 B. Engine Identification
o By referring to the VIN, much information about the vehicle can be
determined.
o Identification numbers are also found on the engine.
o Some manufacturers use tags or stickers attached at various places, such as the
valve cover or oil pan.
o Blocks often have a serial number stamped into them.
o Service manuals typically give the location of the code for a particular engine.
o The engine code is generally found beside the serial number.
o The engine code will help you determine the correct specifications for that
particular engine.

Figure 1‑12 Engine Identification

 1.7 Preparing service work activity plan
o Specifications are included as part of the service manual.
o Specifications are technical data, numbers, clearances and measurements used to
diagnose and adjust automobile components.
Examples of specifications include valve clearances, spark plug gaps, and tire
pressure, number of quarts of oil, ignition timing and size of engine.

Figure 1‑13 Engine ID number

 A.Types of specifications

General Engine Specification– This specifications identify the size and style of the
engine. They include cubic inch displacement, engine codes, fuel system settings, bore
and stroke, horsepower, torque, compression ratio, and normal oil pressure.

Tune-Up specifications – This specification helps identify adjustments necessary for

tune-up on the vehicle. This includes spark plug gap, firing order, degrees of ignition
timings, fuel system settings and fuel pump pressure.

Capacity Specifications –This specification includes identifying the capacity of

different fluids on the vehicle. This includes cooling capacity, number of quarts of oil,
fuel tank size, transmission transaxle capacity, and rear axle capacity.
Overhaul and Maintenance Specifications – This specification used to aid technician
in servicing the vehicle. This include distributor advance at different speeds, valve seat
angles, valve stem clearance, piston measurements, ring end gaps, bearing clearances,
shaft end play and many more.
Torque Specification – It is important to torque each bolt or nut correctly when
replacing or installing a component on the automobile. Torque specifications are
used for this purpose. This torque specification should be used in place of any
standard bolt and nut torque specification.

Owner’s manual

An owner’s manual or an operator’s manual is a booklet that comes with a new car.

This manual usually explains how to operate the automobile’s control and

accessories. In addition the owner’s manual provides a great deal of technical

information that can be useful to the technician.

In an owner’s manual a vehicle maintenance procedure is provided so that the owner

will know when to get needed service.
 1.8 Purpose of Periodic Maintenance

An automobile is constructed from a large number of parts, which can become worn
down, weakened or corroded to lower the performance, depending on the conditions
or the length of use. Constructed parts, which can be estimated that performance goes
down, are needed to have a periodic maintenance, then adjust or replace to maintain
the performance. By carrying out periodic maintenance, the following results can be
achieved, ensuring the customer's trust and peace-of-mind:
1. Much larger problems with the vehicle that may occur later can be avoided.
2. The vehicle can be maintained in a state which is in adherence to legal
regulations.
3. The life of the vehicle can be extended.
 4. The customer can enjoy an economic and safe driving experience.
T, R, I, A, L stand for symbols of maintenance operation.
T=Tighten to specified torque
R=Replace or change
I=Inspect and correct or replace as necessary
A=Check and/or adjust as necessary
L=Lubricate

Service intervals
Service intervals are decided according to the distance traveled and the period elapsed since
the previous service. For example, if the maintenance schedule for a particular part is stated
as 40,000 km or 24 months, maintenance falls due at the point at which either of these
conditions is met. The vehicle is therefore due for service after either: Driving 40,000 km/12
months ( ) after its previous service or driving 5,000km/24 months ( ) after its previous
service. If the vehicle is being used under any of the following conditions, frequent
maintenance will be necessary:
 1.9 OHS and Hazard identification
OHS (occupational health and safety) is a cross disciplinary area concerned with
protecting the safety, health and welfare of people engaged in work or
employment. The goal of occupational health and safety (OHS) is:-
 To protect every working man against the dangerous of injury, sickness or
death through safe healthful working condition.
 To protect co-workers, employers, customers, suppliers and other members of
the public who are impacted by the work place environment.
The requirements of OHS are:-
 Safety
 Personal protective equipment/ need/
 First aid
 Fire extinguisher
 Hazardous materials
 Unit Two: Remove and disassembled system assemblies

This unit to provide you the necessary information regarding the following content

coverage and topics:

This guide will also assist you to attain the learning outcomes stated in the cover

page. Specifically, upon completion of this learning guide, you will be able to:

 Service and maintenance schedules and job order

 Overviewing of service technique

 Disassembling engine exterior assembly

 Removing engine systems and assembly

 2.1 Service and maintenance schedules and job order
o Automobiles need maintenance from time to time.

o Like humans are required to maintain hygiene, similarly automobiles also need to
be kept clean.

o Automobiles have to run on dirty roads and in a polluted environment.

o Therefore, there is a need for regular maintenance and servicing of automobiles,

which is usually done in auto workshops or auto service stations.

o In this Unit, you will understand the concept of vehicle maintenance and servicing.

o Every new vehicle comes with a vehicle maintenance manual.

o The owner of the vehicle is expected to read and use this manual, as it mentions
vehicle maintenance.
 A.Vehicle Maintenance and Servicing

o Tips during driving. It has been noticed that after getting a car or
vehicle, the owners do not care much about a regular car or vehicle
maintenance.
o Even if the owners regularly service their vehicle, the vehicle
maintenance tips given in the vehicle maintenance manual increases
the longevity or life of the vehicle to a great extent.
o Vehicle maintenance and servicing is carried out when the vehicle
completes certain kilometers on its normal running or when the
vehicle does not give proper performance.
 B. Daily Inspection (DI)
It is the responsibility of a driver or owner of a vehicle to carry out the
following inspection and checks daily, before starting the engine, to
avoid any type of breakdown on the road.

a) Check tire pressure in all the tires visually or by hitting the tire wall
with the help of a stone and judge the sound
b) Check the radiator’s coolant level
c) Check the fan belts for looseness
d) Check the level of engine oil
e) Check the windscreen, rear‑view mirror and rear window glass for
their cleanliness
 C. Maintenance Check-up
When one plans a long distance travel, it is necessary to carry out a
routine check‑up. One should read the vehicle maintenance manual for
clarity. Some important check‑ups are done for better maintenance

 Topping of oil level

 Proper tension of belt
 Battery for cleanliness and level of electrolyte
 Brakes
 Air conditioning
 Topping up of coolant, if required, in the coolant reservoir
 Checking the serviceability of cooling system hoses
 Proper tire inflation pressure
 2.2 Overview of service techniques
A.Visual check

o A visual inspection report form is completed by quality assurance inspectors to

document pass/fail decisions on visually inspected products based on set defect
criteria.

o Use this checklist to effectively indicate product ID and location, capture photo
evidence of products and/or defects, determine pass/fail decisions based on a
reference image, identify visual defects based on defect criteria, and complete the
visual inspection with a digital signature.

B. Sound checks

o Diagnosing engine noise is often one of the most difficult tasks you can deal with.
Most of the noises that come from the engine can be described by such words as:
 Piston Ring Noise

Sounds like: Clicking noise during acceleration.

Common causes: Low ring tension, broken rings, or worn cylinder

walls Try troubleshooting each cylinder by removing the spark plugs
and adding a spoonful of engine oil to each cylinder.

Now crank the engine quite a few revolutions to allow the oil to go
down past the rings. Install the spark plugs and start the motor. If the
noise is lessened then the rings are likely the source of the problem.

 Piston Slap

Sounds like: Continuous muffled, hollow sound.

Common causes: Excessive piston-to-wall clearance, worn cylinders or
inadequate oil. A continued piston slap noise indicates that the engine
needs service. Still, if the sound is only heard when the engine is cold, it
is probably not a serious issue.

 Crankshaft Knock

Sounds like: Dull, heavy, metallic knock under load.

Common causes: Worn bearings; main, rod, or thrust.

Damaged or worn main bearing noise is loudest under heavy load. Check
your oil dipstick for any metal reflections. Metal shavings in the oil is
one of the first indications of your main bearing material sloughing off.
Replace any worn bearings with new ones.
 Valve train Noise

Sounds like: Regular clicking noise at half-speed.

Common causes: Excessive valve clearance or defective valve lifter.

o You can check your clearances by inserting a thickness gauge between
the lifter or rocker arm and the valve stem.
o If the noise is reduced, then the cause is excessive clearance and you
will want to make the correct adjustments.
o If the noise persists, then it is most likely rough cams or worn lifter
faces.
o You might also want to look for loosely moving lifters in their bores
and weak valve springs.
 Detonation

Sounds like: High-pitched metallic pinging noise.

Common causes: Improper timing, lean air/fuel ratio, or improper

octane.You can prevent detonation by increasing the octane level of your

fuel, reducing manifold pressure, enriching the air/fuel mixture, or

obstructing the ignition timing. Detonation can often be a common

phenomenon in forced induction applications.

For some operations, you can consider an aftermarket water injection

system.
 Connecting Rod Noise

Sounds like: Light knocking or pounding sound.

Common causes: Misaligned rod, inadequate oil, or worn bearing or crankpin.

A cylinder-balance test can single out the faulty connecting rod. With the engine
running, this test essentially shorts out the spark plugs one cylinder at a time.

Soon, you can narrow down the bad connecting rod as the sound will be lessened when
its base cylinder is no longer delivering power.

 Piston Pin Noise

Sounds like: Metallic, double knock at idle.

Common causes: Worn bushing, worn or loose piston pin, or inadequate oil.

Conduct a cylinder-balance test like described above to discover the distressed

components.
 2. 3 Valve Adjustment
o To check the clearance of any valve accurately, hot or cold, you must rotate the
engine so that the valve is fully closed and the heel, or base circle, of the came lobe
is on the tappet.
o This provides maximum clearance. Insert a flat feeler gauge of the specified
thickness between the valve stem and the rocker arm or cam follower.
o Obviously the clearances should be checked when they are at their widest
which ,with most overhead camshaft arrangements is no problem for once the cover
has been removed the actual cams can be seen the gap is at its widest the lobe of the
cam is pointing directly away from the valve or rocker.
o In overhead valve layouts it’s rather more difficult because the camshaft cannot be
seen with these or any or similar layout there is some method of setting the gap at
its widest.

Figure 2‑1 Valve Adjustment

 A.Valve identification

o Usually the specified clearance at the exhaust valve will be greater than that of the inlet,
which means that it is important to be able to differentiate one the other.

o One way of doing this is to note the location of the valve in relationship to the manifold
braches at the cylinder head.

o Example if the exhaust manifold branches terminate at the end of the cylinder head, then the
first & the last valves are both exhaust.

o The valve layout of a typical four cylinder engine would be E,I,I E,E,I,I,E. Where E
=Exhaust &I= Intake.

o A further method of identifying which valve is which is to turn the engine over in its normal
direction of rotation and watch the valves (or rockers), at each cylinder, the exhaust valve will
open &close, will be immediately followed by the inlet.

o The engine can then be turned through nearly a complete revolution before the exhaust will
open.
Excessive valve clearance would result in:

 Presence of a regular taking sound: the noise can become more of a

general clatter emanating from the top of the engine, if more than one
valve clearance is excessive.
 The valve is not fully open: The valve opens too late & closes too early.
 The valve is returned to its seat much faster than it would normally do. In
severe cases this can result in the head of the valve breaking off causing
extensive engine damage.
 With some arrangements, an indentation may being created in the rocker
(tinge pad).
 When the valve clearance increases it might cause engine noise, increased
emission, or decreased engine performance.
 2.4 Disassembling engine exterior assembly

 Detach the injection pump and high-pressure lines.

 The air compressor should be removed.
 If the engine have oil cooler, remove the oil cooler.
 Remove oil and fuel filters.
 Remove the alternators and its driving belts.
 Remove the starter motor and its wire harness
 Remove steering gear fluid pump.
 Detach the water pump from its mounting part.
 Remove the intake manifold and exhaust manifold with the turbo charger.
 Remove all injectors and glow plugs
 Engine temperature and oil pressure senior should be removed.
 2. Removing and Disassemble engine systems

2.5.1 Cooling system

• The cooling system keeps the engine at its most efficient
temperature at all speeds and operating conditions.

• Burning fuel in the engine produces heat. Some of this heat

must be taken away before it damages engine parts.

• This is one of the three jobs performed by the cooling system.

It also helps bring the engine to normal operating temperature
as quickly as possible.

• In addition, the cooling system provides a source of heat for

the passenger compartment heater.
 1.Types of cooling systems
•Air-cooled
Air-cooled: Some older cars, and very few modern cars, are air-cooled.
• Instead of circulating fluid through the engine, the engine block is covered in
aluminum fins that conduct the heat away from the cylinder.
• A powerful fan forces air over these fins, which cools the engine by transferring
the heat to the air.

Figure 2‑2 Air-cooled engine

 Liquid-cooled
• The cooling system on liquid-cooled cars circulates a fluid through pipes and
passageways in the engine.
• As this liquid passes through the hot engine it absorbs heat, cooling the engine.
• After the fluid leaves the engine, it passes through a heat exchanger, or radiator,
which transfers the heat from the fluid to the air blowing through the
exchanger.

Figure 2‑3 Liquid-cooled engine

 A. Cooling system problem
a) Engine overheating

• The most common cooling system problem is overheating.There are

many reasons for this.

• Diagnosis of this condition involves many steps, simply because

many things can cause this problem.

• Basically, overheating can be caused by anything that decreases the

cooling system’s ability to absorb, transport, and dissipate heat:

• The first step is to determine whether the engine is indeed

overheating. Top causes of engine overheating (1).mp4
 Condition Cause
Overheats in heavy traffic or ■ Low coolant level

after idling for along time ■ Faulty radiator cap

■ Faulty thermostat

■ Cooling fan is not turning on

■ Restricted airflow through the radiator

■ Leaking head gasket

■ Restricted exhaust

■ Water pump impeller is corroded

Overheats when ■ Radiator and/or block are internally clogged with rust, scale, silt, or gel

■ Restricted airflow through the radiator

driving at speed, or
■ Faulty radiator cap
after repeated heavy ■ Faulty thermostat

acceleration ■ Radiator fins are corroded and falling off

■ Water pump impeller is corroded

■ Dragging brakes

Overheats any time or ■ Low coolant level

■ Faulty radiator cap

Erratically
■ Faulty thermostat

■ Temperature sender or related electrical problem

■ Cooling fan is not turning on

 Overheats shortly after ■ Temperature sender or related electrical problem
the engine is started
Seems slightly too hot ■ Radiator and/or block are internally clogged with rust, scale,
silt, or gel
all of the time; gauge
■ Restricted airflow through the radiator
nears the red zone at
■ Faulty radiator cap
times
■ Faulty thermostat
■ Radiator fins are corroded and falling off
■ Collapsed lower radiator hose
■ Cooling fan is not turning on
Bubbles in the coolant ■ Faulty radiator cap
expansion tank ■ Failed head gasket
Air in the radiator but the ■ Coolant leak
expansion tank is full
■ Faulty radiator cap
■ Air in the system
■ Faulty seal between the radiator cap and expansion tank
■ Failed head gasket
a) Check for external leaks
i. External leaks

Usual areas of leakage are water manifolds, radiator seams, water pumps, freeze plugs and all
those connections. The condition of radiator hoses should be carefully scrutinized for possible
deterioration from age and/or wear from rubbing against accessory brackets, etc. Be aware
that in many cases radiator hoses wear from the inside out, so outside appearance can be
deceiving.

 Cracked cylinder block

 Faulty radiator cap
 Dented radiator inlet of outlet tube
 Radiator leak
 Cracked or porous water pump housing
 Water core leak
 Loose core hole plug in cylinder block
 Cracked thermostat housing
ii. Internal leaks

Pull the oil dipstick and check for evidence of coolant. It will show up as minute
droplets or sludge and should be easy to spot. This could indicate a cracked head,
block or blown head gasket.
A. Cooling system inspection and test
a) Inspecting Cooling System for Leaks

1. Fill the radiator and engine with coolant, and attach a radiator cap tester to
the water outlet.

2. Warm up the engine.

3. Pump it to 118 kPa (1.2 kgf/cm2, 17.1 psi), and check that the pressure
does not drop. If the pressure drops, check the hoses, radiator or water
pump for leaks. If no external leaks are found, check the heater core,
cylinder block and head.
 B. Temperature Test

• A temperature test can be performed with an infrared temperature sensor,

thermometer, or temperature probe.
• The latter may be a feature of a digital multi-meters (DMM).
• A temperature test allows for monitoring temperature change through the
cooling system.
• When a cold engine is started, the opening temperature of the thermostat can be
observed as the engine warms.
C. Radiator Checks
• Cold spots on the radiator indicate internal restrictions. In most cases, this
requires removal of the radiator so it can be deeply flushed or replaced.
• Normal cooling system flushing will normally not remove the restrictions.
• The restrictions are typically caused by internal corrosion or a build-up of scale
and lime.
D. Checking Hoses

• Carefully check all cooling hoses for leakage, swelling, and chafing. Also
replace any hose that feels mushy or extremely brittle when squeezed firmly.

• When a hose becomes soft, it is deteriorating and should be replaced before

more serious problems result.

• Hard hoses will resist flexing and may crack rather than bend and should be
replaced.

E. Checking Fans and Fan Clutches

• To confirm the diagnosis, start with this simple test: Spin the fan as hard as
you can on an engine that has not been started that day.
• If the fan rotates more than five times, you can bet the clutch is bad.
• You should feel some resistance and the fan may spin up to three times,
depending on the ambient temperature.
 G. Thermostat
o If the thermostat is stuck open or closed, you may think the best option is to lose it
and take it to a mechanic for diagnosis.
o I have good news.
o I will show you how to check for bad thermostats in a car without removing them.
o One common cause of overheating in a car is a faulty thermostat.
o If you suspect this component, inspect it to see if it is the culprit.
o Here’s how to check a car thermostat without removing it.
 2.5.2 Lubrication system
• The lubricating system supplies lubricating oil to all moving parts in the engine.
• It also control of friction and wear by the introduction of a friction–reducing film
between moving surfaces in contact.
• Lubrication as a substance lubricated material freely moving, reciprocating, back
and forth movement between two hard body materials.
• System a way set of things working together as a mechanism.

Figure 2‑4 Lubrication system

A. Purpose of Lubricants
1. Minimize Friction – the oil must form a film between highly loaded moving parts.
2. Prevent Wear – the must protect highly loaded parts which can wear out when the fluid film
is very thin (boundary lubrication).

3. Act as a coolant – the oil must remove heat generated both inside and outside the equipment.
4. Act as a Hydraulic Medium – the oil doesn’t have this job in all applications, but it is not
uncommon for the lubricating oil to be part of the hydraulic system.

5. Prevent Corrosion – The oil must protect precision parts made of various metals, which are
vulnerable to rust and corrosion.
6. Prevent formation of deposits – lubricants are designed to resist formation of deposits (like
sludge and varnish), which can accumulate in the lubricating system and interfere with the
oil’s ability to lubricate.
7. Carry away contaminants – the oil often wear in the process of carrying contaminants to the
filter. Contamination is the major reason oils must be changed. Contaminants can come from
both internal and external sources.
 Properties of Lubricating Oil
•Proper Viscosity – means to measure the oil’s resistance to flow. A low-viscosity
oil is thin and flows easily. A high-viscosity oil is thicker. It flows more slowly.
•Viscosity Index – this is a measure of how much the viscosity of an oil changes
with temperature.
•Viscosity Numbers – lubricating oils either in single or multi-viscosity oils are
rated according to its numbers. SAE 30 or SAE 40 are examples of a single-
viscosity oil and SAE20W50 is also an example of a multi-viscosity oil. The
letter W indicated in multi-viscosity oil stands for Winter Grade and the word
SAE means
Society of Automotive Engineers.
•Resistance to Carbon Formation and Oil Oxidation – when oil is refine,
chemicals are added to fight carbon formation and oxidation. These can occur at
the high temperatures inside the engine.
•Corrosion and rust Inhibitors – these are additives that are put in the oil to help fight
corrosion and rust in the engine.

•Foaming Resistance – the churning action of the crankshaft causes the oil to foam or
aerate thus reduces the lubricating effectiveness of the oil. As a result, an additive is
mix to prevent the oil to foam.

•Detergent-Dispersant – These additives are similar in action to soap. They loosen and
detach particles of carbon and grit from engine parts.

•Extreme-pressure Resistance - this is another additives put into the oil to improve the
resistance of the oil film to penetration.

•Energy-Conserving Oil – this is a property of an oil which reduces fuel consumption

when compared to engine operation.
•Synthetic Oil – these oils are made by chemical processes and do not necessarily
come from petroleum. This is a property of an oil which tolerates heat better than other
oils while producing less sludge and carbon deposits.
 Types of Lubricating System
Splash Type – it refers to the system in which the oil is being splashed from the oil
pan into the lower part of the crankcase. Usually, the connecting rod has a dipper
that dips into the crankcase oil each time the piston reaches BDC. Likewise, usually
used in a smaller like a single cylinder engine.

Figure 2‑5 Splash Type

Pressure Feed Type – this type of lubricating system connotes that
the engine parts are lubricated by oil fed under pressure from the oil
pump.

Figure 2‑6 Pressure Feed Type

A. Component Parts of the Lubricating System

1) Crankcase / oil pan – it is an iron or aluminum casting enclosing the

crankshaft; it is usually considered as the storage of oil in the engine.

2) Oil Pump – it refers to a pump, which circulates lubricating oil from the
engine’s sump through the lubrication system. Likewise, an oil pump has of
three kinds, to wit:
Rotary pump: the rotary pump has an inner rotor with lobes that match similar
shaped depressions in the outer rotor.
• The inner rotor is off center from the outer rotor.
• As the oil pump shaft turns, the inner rotor causes the outer rotor to spin.
• The eccentric action of the two rotors forms pockets that change size.
• A large pocket is formed on the inlet side of the pump.
• As the rotors turn, the oil-filled pocket becomes smaller, as it nears the outlet of
the pump.

Figure 2‑7 Rotary pump

The gear pump consists of two pump gears mounted within a close-fitting housing.
• A shaft, usually turned by the distributor, crankshaft, or accessory shaft, rotates
one of the pump gears.
• The gear turns the other pump gear that is supported on a short shaft inside the
pump housing.

Figure 2‑8 Gear type pump

 The crescent pump
• The crescent pump has external toothed gear meshed with an internal toothed gear.
• Some of the gears teethes are in mesh, the others are separated by a crescent
shaped part of the pump housing.
• The suction and the discharge cavities are also separated by a crescent - shaped
body.
• The pump is mounted on the front of the cylinder block so that the pump is driven
directly from the crankshaft.

Figure 2‑9 Crescent pump

 Oil Pickup and Strainer
• The oil pickup is a tube that extends from the oil pump to the bottom of the oil pan.
• One end of the pickup tube bolts or screws into the oil pump or to the engine block.
• The other end holds the strainer.
• The strainer has a mesh screen suitable for straining large particles from the oil and
yet passes a sufficient quantity of oil to the inlet side of the oil pump.

Figure 2‑10 Oil Pickup and Strainer

 Oil Filter
• The oil filter removes most of the impurities that have been picked up by the oil,
as it circulates through the engine.
• Designed to be replaced readily, the filter is mounted in an accessible location
outside the engine.

Figure 2‑11 Oil Filter

 Oil Galleries
• Oil galleries are small passages through the cylinder block and head for lubricating
oil.
• They are cast or machined passages that allow oil to flow to the engine bearing and
other moving parts.
• The main oil galleries are large passages through the center of the block.
• They feed oil to the crankshaft bearings, camshaft bearings, and lifters.
• The main oil galleries also feed oil to smaller passage running up to the cylinder
heads.

Figure 2‑12 Oil Galleries

 Oil Pressure Warning Light
• The oil pressure warning light is used in place of a gauge on many vehicles.
• The warning light, although not as accurate, is valuable because of its high
visibility in the event of a low oil pressure condition.
• Because the engine can fail or be damaged in less than a minute of operation
without oil pressure, the warning light is used as a backup for a gauge to attract
instant attention to a malfunction.

Figure 2‑13 Oil Pressure Warning Light

Oil cooler
• Oil cooler is a heat exchanger which is either air cooled type or liquid cooled
type.
• In air-cooled oil cooler, oil flow through heat exchanger tubes and coolant (air)
passing over the tubes where as in liquid cooled cooler, both oil and coolant
(water), the two being separated by tubes or baffles, flow through heat exchanger.

Figure 2‑14 Oil cooler

A. Lubricating system problem diagnosis

To troubleshoot an engine lubricating system, begin by gathering information on the

problem. Ask the operator questions. Analyze the symptoms using your understanding
of system operation.
The four problems most often occur in the lubrication system are as follows:
1. High oil consumption (oil must be added frequently)
2. Low oil pressure (gauge reads low, indicator light glows, or abnormal engine
noises)
3. High oil pressure (gauge reads high, oil filter swelled)
4. Defective indicator or gauge circuit (inaccurate operation or readings) When
diagnosing these troubles, make a visual inspection of the engine for obvious
problems.
5. Check for oil leakage, disconnected sending unit wire, low oil level, damaged oil
pan, or other troubles that relate to the symptoms.
A. High Oil Consumption
If the operator must add oil frequently to the engine, this is a symptom of high oil
consumption. External oil leakage out of the engine or internal leakage of oil into
the combustion chambers causes high oil consumption. A description of each of
these problems is as follows:
 External oil leakage—detected as darkened oil wet areas on or around the
engine. Oil may also be found in small puddles under the vehicle. Leaking
gaskets or seals are usually the source of external engine oil leakage.
 Internal oil leakage—shows up as blue smoke exiting the exhaust system of
the vehicle. For example, if the engine piston rings and cylinders are badly
worn, oil can enter the combustion chambers and will be burned during
combustion
B. Low Oil Pressure
Low oil pressure is indicated when the oil indicator light glows, oil gauge reads low,
or when the engine lifters or bearings vibration. The most common causes of low oil
pressure are as follows:
1. Low oil level (oil not high enough in pan to cover oil pickup)
2. Worn connecting rod or main bearings (pump cannot provide enough oil volume)
3. Thin or diluted oil (low viscosity or fuel in the oil)
4. Weak or broken pressure relief valve spring (valve opening too easily)
5. Cracked or loose pump pickup tube (air being pulled into the oil pump)
6. Worn oil pump (excess clearance between rotor or gears and housing)
7. Clogged oil pickup screen (reduce amount of oil entering pump)
A low oil level is a common cause of low oil pressure. Always check the oil level
first when troubleshooting a low oil pressure problem.
C. Indicator or Gauge Problems
• A bad oil pressure indicator or gauge may scare the operator into believing there are
major problems.
• The indicator light may stay on or flicker, pointing to a low oil pressure problem.
• The gauge may read low or high, also indicating a lubrication system problem.
• Inspect the indicator or gauge circuit for problems.
• The wire going to the sending unit may have fallen off.
• The sending unit wire may also be shorted to ground (light stays on or gauge always
reads high).
• To check the action of the indicator or gauge, remove the wire from the sending
unit.
• Touch it on a metal part of the engine.
• This should make the indicator light glow or the oil pressure gauge read maximum.
If it does, the sending unit may be defective.
2.5.3 Exhaust Gas System
• When the combustion ends in each cylinder, the exhaust gas must be collected,
cleaned, quieted, and then discharged into the air.
• This is the job of the exhaust system. It performs these tasks while carrying the
exhaust gases from the cylinders to the atmosphere.
• This system includes the exhaust manifold, exhaust pipe, catalytic converter,
muffler or silencer, resonator (on some cars), and tail pipe.
• The exhaust system has also flexible mountings that allow for engine movement
and also prevent exhaust vibration from being transmitted to the body.
• They also allow thermal expansion of the system.

Figure 2‑15 Exhaust Gas System

Exhaust system component
A. Exhaust Manifold
• The exhaust manifold is made of cast iron and is bolted over the exhaust ports of
the engine, usually alongside the intake manifold pipe.
• It provides heat to the intake manifold. This heat further vaporizes the fuel in the
intake manifold.
Heat Control valve (or) Heat-Riser Valve

Figure 2‑16 Heat Control valve (or) Heat-Riser Valve

• During cold-engine operation, the gasoline must be vaporized before entering the
cylinders.
• If the fuel is not properly vaporized, drops of gasoline will enter the cylinders.
• They will wash down the cylinder walls and remove the oil.
• This causes the walls, pistons, and piston rings to wear quickly.
• The heat control valve helps to vaporize the cold gasoline when the engine is
cold.

B. Exhaust Pipe
The exhaust pipe is a long pipe leading from the exhaust manifold to the muffler.

C. Catalytic converter
It is discussed under exhaust gas treatment.
 D. Muffler
• The exhaust gas emerges in a pulsating flow and therefore causes marked
vibration in the exhaust pipes and mufflers (silencers).
• The muffler, located between the catalytic converter and the resonator or tail
pipe, contains perforated pipes, baffles, and resonance chambers.
• Its purpose is to reduce the pressure pulses and to quiet or muffle the noise of the
exhaust.
• Without a muffler, the exhaust gas pulsations would roar very loudly.

Figure 2‑17 Muffler silencing operation

E. Resonator
• The resonator is designed to eliminate sounds at a particular frequency which
bounce off the inside of the device canceling each other.
• It is used to further muffle the noise of the exhaust gases. It is also called
secondary muffler.
F. Tail Pipe
• The tail pipe is a pipe that carries the exhaust gases from the muffler to the rear
of the vehicle.
• This pipe may be a separate unit or an integral part of the muffler when the
muffler is located near the rear of the vehicle.

B. Treating the exhaust gas

• Treating the exhaust gas means that some 'cleaning' of the exhaust gas occurs.
• It takes place after the exhaust gas leaves the engine cylinders and before it exits the
tail pipe and enters the atmosphere.
• This reduces the amount of HC, CO and NOx content in the exhaust gas.
• The exhaust gas is treated in two different ways.
• One is by injecting the fresh air into the exhaust system.
• The other is by sending the exhaust gas through a catalytic converter.
 1. Air-Injection (AI) & Air-Suction (AS) Systems
• In this method, fresh air is supplied to the exhaust manifold by an air injection
pump. So that it provides additional oxygen to burn HC and CO coming out of
the cylinders.

Figure 2‑18 Air-Injection (AI) & Air-Suction (AS) System

 2. Air-Aspirator (or) Air-Suction System
• Some engines equipped with a catalytic converter use an air-aspirator system to
deliver fresh air to the exhaust system.
• An air-aspirated valve is located in the tube between the air cleaner and the
exhaust manifold or catalytic converter.

Figure 2‑19 Air-Aspirator (or) Air-Suction System

3. Catalytic Converter
• Catalytic converters provide another way to treat the exhaust gas.
• These devices located in the exhaust system, convert harmful gases into harmless
gases.
• Inside the catalytic converter, the exhaust gases Passover a catalyst.
• A catalyst is a material that causes a chemical reaction.
• In effect, the catalyst encourages chemicals to react with each other.
• The metals such as platinum and palladium are act as oxidizing catalysts and
rhodium as reducing catalysts.

Figure 2‑20 Catalytic Converter

• There are three general categories of catalytic converters.
• These are oxidizing, reducing, and three way.
• The oxidizing converter handles HC and CO, using platinum or palladium as the
catalysts.
• The reducing converter handles NOx using metal rhodium. It splits oxygen from
the nitrogen. The NOx becomes harmless nitrogen (N2) and oxygen (O).

Figure 2‑21 Two way catalytic convertor Figure 2‑22 Three way catalytic converter
C. Exhaust System Service
• Exhaust system components are subject to physical and chemical damage.
• Any physical damage to an exhaust system part that causes a partially restricted or
blocked exhaust system usually results in loss of power or backfire up through the
throttle plate(s).
• In addition to improper engine operation, a blocked or restricted exhaust system
causes increased noise and air pollution.
• Leaks in the exhaust system caused by either physical or chemical (rust) damage
could result in illness, asphyxiation, or even death.
A. Exhaust System Inspection
• Most parts of the exhaust system, particularly the exhaust pipe, muffler, and
tailpipe, are subject to rust, corrosion, and cracking.
• Broken or loose clamps and hangers can allow parts to separate or hit the road as
the car moves
B. Exhaust Restriction

• Test Often leaks and rattles are the only things looked for in an exhaust system.
• The exhaust system should also be tested for blockage and restrictions.
• Collapsed pipes or clogged converters and/or mufflers can cause these blockages.
• There are many ways to check for a restricted exhaust.
• The sound of the exhaust can indicate a restriction.
• Although this is not the most effective way to determine if thereis a restriction, it is
a good start.
C. Exhaust Leaks

• Exhaust leaks are often identified by sound, although very small leaks can be
difficult to locate.
• One of the most effective ways to identify the source of a leak in the system is the
use of a smokemachine.
D. Exhaust Manifold Servicing

• an exhaust manifold will warp because of excess heat.

• A straightedge and feeler gauge can be used tocheck the machined surface of the
manifold.
• Another problem—also the result of high temperatures generated by the engine—is
a cracked manifold.
• This usually occurs after the car passes through alarge puddle and cold water
splashes on the manifold’s hot surface.
• If the manifold is warped beyondmanufacturer’s specifications or is cracked, it
must be replaced.

E. Replacing Leaking Gaskets and Seals

• The most likely spot to find leaking gaskets and seals is between the exhaust
manifold and the exhaust pipe Most often exhaust bolts are quite rusted and can be
difficult to loosen.
• This is why it is wise to soak the bolts and nuts with penetrating fluid before
attempting to disassemble the system.
• To replace an exhaust manifold gasket, follow the torque sequence in reverse to
loosen each bolt.
F. Replacing Exhaust Pipes
• In most cases, the exhaust system is replaced as a unit.
• Doing this ensures a proper fit and saves much time.
• However, there are times when only a section or component needs
to bereplaced.
• When doing this take care not to damage any surrounding parts.
2.5.4 Fuel system
Automobile engines mostly use two types of fuels gasoline and
diesel fuel. These fuels must reach to the engine cylinders and be
ignited. two basic types of fuel systems are used in automobile
engines
1. Gasoline fuel systems (carburetor and gasoline fuel injection)
 2.1 Gasoline fuel systems
• Gasoline is a hydrocarbon (abbreviated HC), made up largely of hydrogen and
carbon compounds.
• there is an explanation of what happens in the engine when gasoline is burned.In
this system, the carburetor is replaced by a toe body whose only purpose is to
control the amount of air entering the intake manifold.
• Most fuel-injection systems include a fuel pump, fuel lines, an electronic control
unit, and one or more fuel-injection valves.
• The injection valve is a nozzle with a small hole through which fuel is sprayed on a
signal from the electronic control unit.

A. Components
• The carbureted fuel system consists of the fuel tank, fuel pump, fuel filter,
carburetor, intake manifold, and fuel lines.
• The fuel lines are tubes connecting the tank, fuel pump, and carburetor.
• Most of these components are the same in both the carbureted and the fuel-
injection systems.
• Each component is described in following sections.
Carburetor Components
 B. Fuel tank
• The fuel tank is normally located at the rear of the vehicle.
• It is usually made of sheet metal or plastic. It is attached to the frame or body.
• The filler opening of the tank 'is closed by a cap.

Figure 2‑23 Fuel tank

C. Fuel Filters And Screens
• Fuel Systems have filters and screens to prevent dirt in the fuel from entering the
fuel pump or carburetor.
• Dirt could prevent normal operation of these units and because poor engine
performance, filters may be a separate unit connected into the fuel line between the
tank and the fuel pump, or between the fuel pump and the carburetor, or in or on
the carburetor itself.

Figure 2‑24 Fuel Filters and Screens

 D. Fuel gauge

• There are two types of fuel gauges, magnetic and thermostatic.

• Each of these gauges has a tank unit and an instrument panel unit.

Magnetic: - The tank unit in this fuel gauge contains a sliding contact.

• The contact slides back and forth on a resistor as the float moves up

and down in the fuel tank.

• This change the amount of electric resistance the tank unit offers.

• As the tank empties, the float drops and the sliding contact moves to

reduce the resistance.

Thermostatic: - It has a fuel-tank unit much like the magnetic system.

• The tank unit has a float and a sliding contact that moves on a resistor.

• Current flows from the battery through the, resistance in the tank unit.

• When the fuel is low in the tank, most of the resistance is in the circuit.

• Very little current can flow.

• When the tank is filled, the float moves up, and the sliding contact cuts most of the

resistance out of the circuit.

• Now more current flows.

• As it flows through the heater coil in the fuel gauge, the current heats the

thermostat.
 E. Fuel Lines and Hoses
 Fuel lines and hoses carry fuel from the tank to the engine.
 The main fuel line allows the fuel pump to draw fuel out of the tank.
 The fuel is pulled through this line to the pump and then to the carburetor, or
metering section of the injection system.
 F. Air Cleaner
• The fuel system mixes air and fuel to produce a combustible mixture.
• A large volume of air passes through the carburetor or fuel injection system
and engine.
• Air always contains a lot of floating dust and grit.
• The dust and grit could cause serious damage if they entered the engine.
• To prevent this, an air cleaner is mounted at the air entrance of the carburetor
or fuel injection system.
• The two types of cleaners currently used are the wet and dry types.

Figure 2‑25 Wet type air cleaner Figure 2‑26 Dry type air cleaner
 G. Gasoline fuel pumps
Gasoline fuel pump is a device, which delivers fuel from the tank to the carburetor.
Fuel pumps are generally of two types: Mechanical and Electrical pumps.
A. Mechanical fuel pump
• Four stroke spark ignition engines are in most cases equipped with a mechanical
diaphragm type pump.
• The main distinction between the various types of diaphragm pump is the drive
principle: they can be operated by a cam and lever, by levers from pushrod or by a
plunger.
• The pump, figure 1 consists of a spring laded flexible diaphragm, usually made
from laminated synthetic rubber and nylon fabric, sandwiched between an upper
valve- chamber housing and a lower pull-rod housing which is attached to the
engine.
• Built into the upper chamber there are pair of inlet and outlet valves.
Gasoline fuel pumps

Figure 2‑27 Mechanical fuel pump

 B. Electrical fuel pumps
• Electrical fuel pumps have certain advantages over mechanical fuel pumps.
• Fuel is at the carburetor as soon as the ignition switch is turned on.
• The pump can deliver more fuel than the engine will require even under maximum
operating conditions.
• Thus, the engine will never be fuel – starved. They are, therefore, used in many
high performance and heavy- duty application.
• There are various types of electric fuel pumps.
• One of the latest types is mounted in the fuel tank.
• It contains an impeller driven by an electric motor.
• This pushes fuel through the fuel line to the carburetor.
• Other types are mounted in the engine compartment.

Figure 2‑28 Electrical fuel pumps

 2.2 Carburetor terminologies
A. Carburetion
• Carburetion is the mixing of the gasoline fuel with air to get a combustible
mixture.
• The function of the carburetor is to supply a combustible mixture of varying
degrees of richness to suit engine operating connections.
• The mixture must be rich (have a higher percentage of fuel) for starting,
acceleration, and high-speed operation.
• A less rich (leaner) mixture is desirable at intermediate speed with a warm
engine.
• The carburetor has several systems through which .air-fuel mixture II flows
during different operating conditions.
• These systems produce the varying mixtures required for the different operating
conditions.
B. Vaporization

• When a liquid changes to a vapor, it is said to evaporate.

• Water placed in an open pan will evaporate.

• The water changes from a liquid to a vapor, Wet clothes hung on a line dry: the

water in the clothes turns to vapor.

• When the clothes are spread out, they dry more rapidly than when they are

bunched together.

• This illustrates an important fact about evaporation.

• The greater the surface exposed, the more rapidly evaporation takes place. Water

in a tall glass takes longer to evaporate than water in a shallow pan.

• Much more area is exposed in the pan

C. Atomization
• To produce very quick vaporization of the liquid gasoline, it is
sprayed into the air passing through the carburetor.
• Spraying the liquid turns into many fine droplets.
• This effect is called atomization because the liquid is broken up
into small droplets (but not actually into atoms, as the name
implies).
• Each droplet is exposed to air on all sides so that it vaporizes very
quickly.
• Therefore, during normal running of the engine, the fuel sprayed
into the air passing through the carburetor turns to vapor.
D. Venture Effect
• The engine is, in a sense, a vacuum pump. As the pistons move down on the intake strokes,
a partial vacuum is produced in the cylinders.
• A partial vacuum is any pressure less than atmospheric pressure.
• Atmospheric pressure pushes air, or air-fuel mixture, into the cylinders to fill the vacuum.
As the air flows toward the engine cylinders, it must first pass through the carburetor.
• A venturi is located in the air passage through the carburetor. As the air flows through the
venturi, a partial vacuum is produced in it.
• The venturi restricts the flow of air so that the air pressure in the venturi is reduced.
• The air particles before the venturi are at atmospheric pressure (normal air pressure) But as
they move through the venturi, they speed up and spread out (pressure drops, or a partial
vacuum develops).
• The fuel nozzle is located in the venturi. Atmospheric pressure is pushing down on the fuel
in the float bowl.
• Since there is a partial vacuum around the venturi end of the fuel nozzle (the pressure is
lower), atmospheric pressure pushes fuel up through the nozzle and into the air flowing
through the venturi. The fuel sprays out, or atomizes, and quickly turns to vapor.
E. Throttle Valve action
• The throttle valve is a round disk below the venturi and fuel nozzle in the
carburetor.
• The air horn is the round cylinder through which air flows on its way to the
engine cylinders.
• The air picks up a change of fuel vapor while passing through the venturi.

• The throttle valve can be tilted more or less to allow more or less air-fuel
mixture to flow through.
• More air flowing through the venturi increases the venturi vacuum.
• This causes more fuel to flow from the nozzle.
• If the throttle valve is tilted toward the closed position less air will flow.
• The vacuum in. the venturi will be less.
• Therefore less fuel will discharge into the passing air.
F. Air-fuel-ratio requirements
• The fuel system must vary the air-fuel ratio to suit different operating requirements.
• The mixture must be rich (have a high proportion of fuel) for starting.
• It must be leaner (have a lower proportion of fuel for part-throttle medium-speed
operation.
• Ratios, and the speeds at which they are obtained, vary with different cars.
• In the example shown in, a rich mixture of about 9:1 '(9 pounds [4 kg] of air for each
pound [0.45 kg] of fuel) is supplied for starting.
• Then, during idle, the mixture leans out to about 12:1. At medium speeds, the mixture
further leans out to about 15:1 or leaner. Some engines run on mixtures as lean as 20:1. But
at higher speeds, with a wide-open throttle, the mixture is enriched to about 13:1.
• Opening the throttle for acceleration at any speed causes a momentary enrichment of the
mixture.
• The following sections describe the various systems in carburetors that supply the air-fuel
mixture required for different operating conditions.In many late-model cars, the air-fuel
'ratio is controlled electronically. The electronic control systems are explained in the
 2. 3 Carburetor Systems

• The fixed venturi carburetor has six systems and several devices
that provide the correct air-fuel mixture for different operating
conditions. These include:
1. Float System
2. Idle and Low speed System
3. Main-Metering System
4. Power System
5. Accelerator Pump System
6. Choke System
 1. The float system
• This system maintains a steady working supply of gasoline at a constant level in
the carburetor.
• This action is critical to the proper operation of the carburetor.
• Since the carburetor uses differences in pressure to force fuel into the air horn.
• The float system keeps the fuel pump from forcing too much gasoline into the
carburetor bowl.
• The basic parts of the float system are the fuel bowl, the float, the needle valve,
the needle seat, the bowl vent.

Figure 2‑29 Float system

 2. Idle system ( no load operation)
• The throttle valve is closed during engine idling.
• Therefore, the vacuum in the intake manifold (below the throttle valve) is high.
• The vacuum in the intake manifold decreases as the throttle opens.
• The vacuum in the intake manifold draws the air-fuel mixture via the idle port.
• The amount of air –fuel mixture is controlled by an idle-mixture screw.

Figure 2‑30 Idle system

 3. Off idle system (low speed operation)
• The off idle, also known as the part throttle, feeds more fuel into
the air horn when the throttle plate is partially open.

• Air – fuel mixture is drawn from both the idle and low speed ports.

• It is an extension of the idle system.

• It functions above approximately 800 rpm or 20 mph. Without the

off idle system, the fuel mixture would become too lean slightly
above idle.

• The idle system alone is not capable of supplying enough fuel to

the air stream passing through the carburetor.
Off idle system (low speed operation)
4. Acceleration system
• The carburetor acceleration system, like the off idle system, provides extra fuel
when changing from the idle system to the high-speed system.
• The acceleration system squirts a stream of fuel into the air horn when the fuel
pedal is pressed and the throttle plates swing open.
• Without the acceleration system, too much air would rush into the engine, as the
throttle quickly opened.
• The mixture would become too lean for combustion and the engine would stall or
hesitate.
• The acceleration system prevents a lean air-fuel mixture from upsetting a smooth
increase in engine speed.

Figure 2‑31 Acceleration system

5. High-Speed System (Main metering system)
• The, high-speed system, also called the main metering system, supplies the engine
air-fuel mixture at normal cruising speeds.
• As the throttle valve opens further, the vacuum near the throttle valve decreases,
and the flow from the idle and low speed ports stop.
• The fuel is now supplied from the main nozzle.
• As the throttle valve opens wider, air flow, venture throat vacuum, fuel flow.

Figure 2‑32 High-Speed System

 6. Full-Power System
• The full-power system provides a means of enriching the fuel mixture for high-
speed, high-power conditions.
• This system operates, for example, when the driver presses the fuel pedal to pass
another vehicle or to climb a steep hill.
• The full-power system is an addition to the high-speed system.
• Either a metering rod or a power valve (jet) can be used to provide variable, high-
speed air-fuel ratio.

Figure 2‑33 Full-Power System

Full-Power System
7. Choke System
• With the carburetor and engine cold, only part of the fuel evaporates.
• Same fuel condenses on the cold intake manifold walls Extra fuel is needed so
enough will vaporize to produce a combustible mixture.
• To start a cold engine, the carburetor must deliver a very rich mixture.
• The choke valve produces the required fuel enrichment during engine cold start.

Figure 2‑34 Choke system

 2.4 Carburetor accessories

• There are several devices used on carburetors to improve

drivability and economy.

• These devices are as follows: the fast idle solenoid, the throttle

return dashpot, the hot idle compensator, and the altitude

compensator.

• Their applications vary from vehicle to vehicle.

 Fast Idle Solenoid
• A fast idle solenoid, also known as an anti-dieseling solenoid, opens the carburetor
throttle plates during engine operation but allows the throttle plates to close as
soon as the engine is turned off.
• In this way, a faster idle speed can be used while still avoiding dieseling (engine
keeps running even though the ignition key is turned off).
• This is a particular problem with newer emission controlled vehicles due to higher
operating temperatures, higher idle speeds, leaner fuel mixtures, and lower octane
fuel.

Figure 2‑35 Throttle return dashpot Figure 2‑36 Anti dieseling solenoid operation
Throttle Return Dashpot
• The throttle return dashpot, also known as an anti-stall dashpot, acts as a damper to
keep the throttle from closing too quickly when the accelerator pedal is suddenly
released.
• It is commonly used on carburetors for automatic transmission equipped vehicles.
• Without the throttle return dashpot, the engine could stall when the engine quickly
returned to idle. The drag of the automatic transmission could kill the engine.
• The throttle return dashpot works something like a shock absorber. It uses a spring-
loaded diaphragm mounted in a sealed housing.
• A small hole is drilled into the diaphragm housing to prevent rapid movement of the
dashpot plunger and diaphragm. Air must bleed out of the hole slowly.
• When the vehicle is traveling down the road (throttle plates open), the spring pushes
the dashpot plunger forward.
• When the engine returns to idle, the throttle lever strikes the extended dashpot
plunger, and air leaks out of the throttle return dashpot, returning the engine slowly
to curb idle.
• This action gives the automatic transmission enough time to disconnect (torque
converter releases) from the engine without the engine stalling.
Hot Idle Compensator
• A hot idle compensator (figure 2.37) is a thermostatically controlled device that
prevents engine stalling or a rough idle under high engine temperatures.
• The temperature sensitive valve admits extra air into the engine to increase idle
speed and smoothness.
• At normal engine temperatures, the hot-idle compensator valve remains closed,
and the engine idles normally.
• When temperatures are high (prolonged idling periods, for example), fuel vapors
can enter the air horn and enrich the air-fuel mixture.
• The hot idle compensator opens to allow extra air to enter the intake manifold.
• This action compensates for the extra fuel vapors and corrects the air-fuel
mixture.

Figure 2‑37 Hot Idle Compensator

Altitude Compensator

• An altitude compensator is used to change the air-fuel mixture in the

carburetor with changes in the vehicle height above sea level.

• Normally the compensator is an aneroid device (bellows device that

expands and contracts with changes in atmospheric pressure).

• As a vehicle is driven up a mountain, the density of the air decreases.

• This condition tends to make the air-fuel mixture richer.

• The reduced air pressure causes the aneroid to expand, opening an air
valve.

• Extra air flows into the air horn and the air-fuel mixture becomes
leaner.
 2.2 Diesel-Engine Fuel Systems
The automotive diesel-engine fuel system uses injection nozzles or
injectors similar to the fuel injectors in gasoline fuel-injection systems.
The gasoline injectors are solenoid operated. When high pressure is
applied, they open and spray fuel. The diesel fuel system must:
1. Deliver the right amount of fuel to meet the operating
requirements.
2. Time the opening of the injection nozzles so the fuel enters the
engine cylinders at the proper instant. As engine speed increases,
fuel injection must start earlier. This gives the fuel enough time to
burn and produce pressure on the pistons. Without the advance, the
pistons would be over TDC and moving down before the fuel fully
ignites. This wastes fuel and power.
3. Deliver the fuel to the cylinders under high pressure. Injection
pressure must be high enough to overcome the high compression
pressure in the diesel engine. At the end of the compression stroke,
compression pressure may be 500 psi [3447 kPa] or higher.
1. Constructions and operation
• The fuel delivery system has the important role of delivering fuel to the fuel
injection system.

• The fuel must also be delivered in the right quantities and at the right pressure.

• The fuel must also be clean when it is delivered. A typical fuel delivery system
includes a fuel tank, fuel lines, fuel filters, and a pump.

• The system works by using a pump to draw fuel from the fuel tank and passing it
under pressure through fuel lines and filters in the fuel injection system.

• The filter removes dirt and other harmful impurities from the fuel.

• A fuel line pressure regulator maintains a constant high fuel pressure.

• This pressure generates the spraying force needed to inject the fuel.

• Excess fuel not required by the engine returns to the fuel tank through a fuel return
line.
Diesel-Engine Fuel Systems
 Fuel tank
• The fuel tank on commercial vehicles is often made of aluminum or plastic for
reasons of weight.

• It must be corrosion resistant and remain tight at double its operating pressure
(legally specified minimum value = 0.3 bar overpressure).

• Larger tanks often incorporate baffle plates to prevent the fuel from being
displaced excessively when cornering, braking and moving away.

• The drain plug is positioned at the lowest point in the tank.

 Fuel lines
Steel pipes or plastic fuel lines are used in the diesel engines of commercial
vehicles.
  Fuel supply pump
• The fuel supply pump transfers the fuel from the tank to the injection pump.
• On the inline injection pumps often used on commercial vehicles, the fuel supply
pump is a piston-type pump.
• It is flanged onto the injection pump and usually equipped with a hand-operated
pump for venting the fuel system.
• Its task is to deliver the fuel to the injection pump at a pressure of approx. 1 - 2.5
bar.
• The supply pump is driven by a cam located on the injection pump camshaft.
• The higher the pressure in the supply line, the less fuel is pumped.
• This is known as flexible delivery.
• Distributes pumps have integral supply pumps which take the form of vane pumps
or separate diaphragm pumps.

Figure 2‑38 Supply pump

  Fuel filter
• For optimum operation and service life of the diesel fuel injection system, it is
essential that the diesel fuel be carefully filtered.
• The components of the injection pump and the injectors themselves are
manufactured to a precision of a few thousandths of a millimeter.
• Fuel filters must filter out impurities of even this small size if the efficiency of the
fuel injection system is not to be impaired.

Figure 2‑39 Fuel filter

The consequences of poor fuel quality as a result of
contaminated filters are:

 Poorer combustion,
 Poor starting behavior,
 Low engine output,
 Lumpy idling,
 High fuel consumption.
The filter element must be changed at the specified
interval (approx. 30,000 km).
2. Fuel injection system

Depending on the diesel combustion method used, the fuel must be injected into the
combustion chamber at a pressure of between 350 and 1600 bars. The fuel must in
addition be metered with extreme accuracy.

The principal defining characteristics of a modern commercial-vehicle diesel engine are

its fuel consumption, pollutant emissions and noise emissions. For these parameters to
be ideally matched, the start of delivery has to take place with an accuracy of approx.

+-1 °CS. Important criteria for the fuel injection processes are:

 Timing and duration of fuel injection,

 Fuel distribution in the combustion chamber,
 Timing of start of combustion,
 Amount of fuel metered per °CS,
 Overall amount of fuel metered.
 Inline injection pumps
• Inline injection pumps have a separate camshaft and one pump element per engine
cylinder.
• The stroke of the pistons always remains the same.
• The pump rate is regulated via metering ramps.
• The fuel is pumped through a separate high-pressure line to the corresponding
injector for each cylinder of the engine.
• The injection pump camshaft, driven by the engine, controls the injection processes
in the individual injectors.
• A mechanical injection timing device adjusts the start of delivery according to
engine speed, as necessary.
• It rotates the camshaft in relation to the engine crankshaft, thus displacing the start
of delivery.
• The inline injection pump is connected up to the engine oil circuit for lubrication of
the moving pump components.
 Inline injection pumps

Figure 2‑40 Operating principle of the lifting-slide inline injection pump & mechanical in line pump
Distributor-type pumps
• Unlike the inline injection pump, the distributor-type pump has only one pump
element with one piston for all cylinders.

• The piston operates as many strokes as there are cylinders for every revolution of
the crankshaft.

• The simultaneous movement of the piston during the stroke distributes the fuel to
the various inlets and pumps it to the corresponding injectors.

• A mechanical speed governor and a hydraulic injection timing device are

integrated into the distributor pump housing.

• Distributor-type pumps are used on high speed passenger-car and commercial

vehicle diesel engines with an output per cylinder of up to 25 kW.

• The injection pressure is approximately 700 bars. Distributor type pumps with
electronic control are capable of injection pressures as high as 1400 bar.
 Fuel system for Distributor injection pump

Fig. Distributor (VE type) fuel injection pump

 Fuel injectors:
• Fuel injectors should be removed and taken to a qualified diesel engine repair
center to be tested for leakage and spray pattern, if poor engine performance such
as loss of power, rough or uneven running, sudden notice of dark exhaust, or
engine becomes hard to start.
Removing injectors:
1. Clean the area around the injectors before removing.
2. Loosen nuts holding the fuel lines to the injector pump and injector nozzle and
remove fuel lines.
3. Loosen nut on return line adapters and remove adapters.
4. Loosen injectors and remove injectors.

Figure 2‑41 Sectional view of injector

 Replacing injectors:
1. Check to be sure contacts surfaces and area around injectors is clean.

2. Replace injectors in the same cylinder from which they were removed.

3. The torque required to properly seat the injectors will be between 43 and 58
ft./lbs.

4. Replace fuel return lines and secure nuts.

5. Replace all fuel lines and secure all nuts.

6. After all injectors, fuel lines and hoses have been replaced and are secured, the
fuel system will have to be bled.

The fuel injection pump has been set at the factory and should need no adjustment.
Any apparent problem with the pump should be referred to a qualified diesel
mechanic or to a Universal Diesel dealer as advised.
 Bleeding Diesel fuel system
 It will be necessary to bleed the fuel system to achieve a steady air free flow of fuel
if any of the following have occurred.

1. Running out of fuel.

2. If fuel shut off valve is left closed and the engine runs out of fuel.

3. Replacing fuel filter.

4. Fuel injector nozzle or injector pump repair.

5. After repairing or replacing any fuel line.

6. Before putting the engine back into service in the spring, if fuel system has been
drained.

7. Replacement of electric or mechanical fuel pump.

8. Any time air is permitted to enter the fuel system.

 Bleeding procedure:
Be sure to have some means available to catch or absorb any fuel escaping
during the bleeding process so that it will not accumulate in the engine
compartment or bilge.

1. Be sure there is a sufficient supply of fuel in the fuel tank.

2. Open the fuel shut-off valve at the tank.

3. Start the electric fuel pump by turning the ignition key to the "ON" position on
models 18, 20, 25, 30, 50, all models after 1986.

4. Model 15 has a mechanical fuel pump. Therefore, with decompression on, turn
the engine over with the starter. Crank at 10 second intervals while doing steps #5
and 7.

5. Slowly loosen the air bleed plug on the fuel filter, letting air escape until an air
 6. At this time, tighten the air bleed plug on the filter.

7. Slowly loosen the air bleed plug on the injector pump, letting air escape until
an air free flow of fuel is evident. Units with a self-bleed return valve open for a
short period then start engine, as soon as engine runs smooth close valve. Model-
12 has continuous fuel bleeding.

8. At this time, tighten the air bleed plug or knurled knob on the injector pump.

9. The fuel system should now be properly bled and ready for operation. Refer to
starting instructions before attempting to start the engine after bleeding the fuel
system.

CAUTION: Excessive cranking with seal cock valve open can cause water
accumulation in the muffler and possibly back up into the engine. Drain muffler as
needed.
 Injection timing
a) Timing device
1. A large percentage of fuel injection pumps have timing devices incorporated in
them. Varying the time when fuel injection begins will improve diesel engine
performance and fuel economy, for the same reason that varying spark timing will
improve the performance of a gasoline engine.
2. The timing device usually consists of an aluminum casting with mounting flanges
at both ends. A bore in the housing guides and supports the spider assembly. A
timing opening, with a cover, is located in the top of the housing and is used to
observe the position of the timing pointer in relation to the timing mark on the
timing device hub during injection pump timing procedures.
3. The timing device hub, with external left-hand helical splines for engaging the
internal helical splines of the sliding gear, has a tapered bore and keyway. The hub
is secured to the camshaft extension by a woodruff key, nut, and setscrew.
 • The hub is usually counter bored to receive the timing device springs.
• The springs oppose the fly weight forces of the weight and spider assembly.
4. The weight and spider assembly has external right-hand helical splines which mesh
with the internal helical splines of the sliding gear.
• The splined end is machined to receive the end play spacer.
• Three flyweights are pinned to a flange adjacent to the splines.
• The weight and spider thrust plate, located between the flange and the timing device
housing, carries the back thrust of the flyweights and prevents housing wear.
5. The sliding gear has internal left-hand helical splines at one end and internal right
hand helical splines at the other, and meshes with the external splines of both the
weight and spider assembly and the timing device hub.

• Correct assembly of the spline train is ensured by a wide land on both the hub and
weight and the spider assembly.
• The sliding gear has a missing tooth on each set of internal splines to receive the
wide lands.
 Operation:

1. As the engine rotates the weight and spider assembly, centrifugal force

opens the flyweights from their collapsed position against the force of the

three timing device springs.

2. As the flyweights swing out, the sliding gear is forced toward the timing

device hub.

3. The longitudinal movement of the sliding gear on its helical spline causes a

slight change in the rotational relationship of the injection pump to the

engine, causing injection to begin slightly earlier in the power stroke.

Testing Injector Nozzle
Before disassembling an injector an important step is to test it. The injector is
connected to the pressure line of the injector tester, figure and tightened after the air is
removed.

Figure. Injector nozzle tester

Perform the tests in the Following order:-
1. Opening pressure test
2. Leakage or valve-seat test
3. Back leakage test
4. Spray pattern test
 1. Adjusting injection nozzle Opening Pressure
Testing Procedure:

Figure. Opening pressure test.

a) Open the pressure gauge isolator after bleeding the system.

b) Operate the lever of the tester slowly until injection occurs.
c) Observe the pressure gauge and note highest reading just before injection
pressure begins to drop.
 d) Compare the recorded opening pressure reading with manufacturer's

specification. If the actual pressure varies from the standard, the pre-tension

of the pressure spring has to be adjusted. This is done by the adjustment

screw provided, or by adjusting shims of various sizes. Adjusting Shims are

usually available in sizes from 1.0 - 3.0mm thickness and in steps of

0.05mm.

Note

If New Injection Nozzles has to be installed, adjust the opening pressure 5.0 to

10.0 bar above the specified pressure in order to compensate a pressure drop

caused by the short break-in period of the needle valve.

 2. Checking injection nozzle Leakage or Valve-Seat
Testing Procedure:
a. Open the pressure gauge isolator and wipe injector tip dry.
b. Depress the operating level of the tester slowly until the gauge indicates a pressure
of about 10 to 20 bar below the before- measured opening pressure.
c. Maintain this pressure for 10 seconds and observe the injector tip.

Results Figure. Leakage or valve-seat test

If no fuel drop occurs during this time, the needle-valve seat is in good condition. If
there is any evidence of fuel at the tip, the needle-valve seat is defective. The nozzle
assembly should be replaced or overhauled.
3. Checking injection nozzle back Leakage Test

After the leakage or valve-seat test, some manufacturers recommend to perform a

back leakage test.

Testing Procedure:

a. Open the pressure gauge isolator on the tester.

b. Slowly depress the operating lever until stated pressure is shown on the gauge.

c. Release the operating lever and note the time taken for pressure to fall.

The time for the pressure drop can be influenced by: -

1. The fuel temperature

2. The viscosity of the test fluid used

3. The length of the pressure line used.

Results

Generally, a pressure drop from 150 to 100 bar (P  50 bar) within a time not less

than 6 seconds (T6 second), using shelf fluid “C” and maintaining a test

temperature approximately 100 up to 200c indicates a satisfactory injector.

A higher pressure drops than specified can be caused by: -

a. Loose fuel pipe connections

b. High temperatures, causing thinning of the test oil

c. Loose nozzle cap or nozzle holder retaining nut.

d. Dirty or damaged sealing surfaces of the nozzle and/or nozzle holder, which

allows fuel to escape.

4. Checking injection nozzle Spray Pattern
Testing Procedure:
a. Close the pressure gauge isolator on the tester.
b. Move the opening lever at about 1 strokes/second and observe the spray jet. A
nozzle in good condition shows a thin and even cone-shaped jet of spray without
distortion and fine atomized fuel.
c. After this, gradually increase the lever movement to about 2 strokes per second.

Figure. Spray Pattern Test Results

Results

Now a characteristic "chattering or humming" sound should be noticed indicating a

properly working injector. This depends also very much on the test fluid used. If

the injector does not atomize the fuel completely, incomplete combustion, causing

black smoke, a loss in engine power and poor fuel economy, will result, Increased

diesel knock, due to the longer delay period that follows poor atomization, will also

be evident.
 Unit Three: Replace/Reassemble System Assemblies
This unit to provide you the necessary information regarding the following content
coverage and topics:

 Carryout minor adjustments

 Assembling system components
 Conducting post-service/pre-delivery check
This guide will also assist you to attain the learning outcomes stated in the cover
page. Specifically, upon completion of this learning guide, you will be able to:
 Carry out minor adjustments
 Assemble system components
 Conduct post-service/pre-delivery check
 3.1 Carrying out minor adjustments
1. Whenever you change an engine’s oil, you should also do a visual inspection of the
different systems under the hood, including the cooling system.
2. Inspect all cooling system hoses for signs of leakage and/or damage.
3. Replace all hoses that are swollen, cracked, or show signs of leakage.
4. Also, check the front of the radiator for any build-up of dirt and bugs.
5. This can restrict airflow through the radiator and should be removed by thorough
cleaning.
6. The level and condition of the engine’s coolant should also be checked.
7. It should be between the “low” and “full” lines.
8. If the level is too low, more coolant should be added through the cap of the tank,
not the radiator.
9. Bring the level up to the “full” line.
10. Always use the correct type of coolant when topping off or replacing it.
11. Look at the color of the coolant when checking the level.
12. It should be green, or perhaps orange, but it should not look rusty or cloudy.
13. If the coolant looks contaminated, the cooling system should be flushed and new
 3.2 Coolant Condition

• A coolant hydrometer is used to check the amount of antifreeze in the coolant.

• This tester contains a pickup hose, coolant reservoir, and squeeze bulb.

• The pickup hose is placed in the radiator coolant.

• When the squeeze bulb is squeezed and released, coolant is drawn into the reservoir.

• As coolant enters the reservoir, a pivoted float moves upward with the coolant level.

• A pointer on the float indicates the freezing point of the coolant on a scale located

on the reservoir housing.

 3.3 Drive Belts
• Drive belts V-belts and V-ribbed (serpentine) belts are used to drive water pumps, power
steering pumps, air-conditioning compressors, generators, and emission control pumps.

• Heat has adverse effects on drive belts and they tend to over cure due to excessive heat.

• This causes the rubber to harden and crack.

• V-belts ride in a matching groove in the engine’s pulleys.

• The angled sides of the belt contact the inside of the pulleys’ grooves.
• This point of contact is where motion is transferred. As a V-belt wears, it begins to ride deeper
in the groove.
• This reduces its tension and promotes slippage.
• Because this is a normal occurrence, periodic adjustment of belt tension is necessary.
• Drive belts can be used to drive a single part or a combination of parts.
• An engine can have three or more V-belts.
• In some cases, two matched belts are used on the same pulley set.
• This increases the strength of the belt and pulley connection and provides redundancy in case
a belt breaks.
 Inspection Even the best drive belts last only an average of 4 years.
• That time can be shortened by several things; most of these can be found by inspecting the
belts.
• Check the condition of all of the drive belts on the engine.
• Carefully look to see if they have worn or glazed edges, tears, splits, and signs of oil
soaking.
• If these conditions exist, the belt should be replaced.
• Also inspect the grooves of the drive pulleys for rust, oil, wear, and other damage.
• If a pulley is damaged, it should be replaced. Rust, dirt, and oil should be cleaned off the
pulley before installing a new belt.
• Misalignment of the pulleys reduces the belt’s service life and brings about rapid pulley
wear, which causes thrown belts and noise.
• Undesirable side or end thrust loads can also be imposed on pulley or pump shaft bearings.
• Check alignment with a straightedge. Pulleys should be in alignment within 1⁄16 inch (1.59
mm) per foot of the distance across the face of the pulleys.
 Belt Tension A quick check of a belt’s tension can be made by locating the longest

span of the belt between two pulleys.

• With the engine off, press on the belt midway through that distance.

• If the belt moves more than ½ inch per foot of free span, the belt should be adjusted.

• Keep in mind that different belts require different tensions.

• The belt’s tension should be checked with a belt tension gauge.

• The tension should meet the manufacturer’s specifications.

• Many engines are now equipped with a ribbed v-belt, which has an automatic

tensioning pulley; therefore, a tension adjustment is not required.

 Using service information proper belt tightening procedures and specifications are
given in the specification section of most service manuals.

Figure 3‑1 checking Belt

 3.4 Assembling system components
Connect the injector nozzle leak off pipe assembly
Connect the cooling system
Connect the exhaust pipe
Connect the injector nozzle leak off pipe assembly
Connect the fuel pipes from the fuel injection pump outlet and inlet to filter
Connect fuel pipe from fuel lift pump outlet to fuel filter. Remove fuel filter
Connect high pressure fuel pipes and nozzles
Connect fuel pipe and electrical lead at the thermostat.
Connect air filter and / or connecting hose
Connect induction and exhaust manifold
Connect the cooling system
Connect fuel pipe and electrical lead at the thermostat.
Remove air filter and / or connecting hose
Remove induction and exhaust manifolds
 3.5 Conducting post-service/pre-delivery check

1. Document result with evidence

• Documentation provides valuable descriptions of an organization’s development,
acquisition, and operating environments and significantly enhances an organization’s
ability to administer, operate, and maintain technology systems.
• Primary advantages for technicians’ involve having access to operation manuals and
on-line application help features.
• Documentation enhances administrators’ and technicians’ ability to maintain and
update systems efficiently and to identify and correct programming defects.
• Developing and maintaining current, accurate documentation can be complicated,
time consuming, and expensive.
• However, standardized documentation procedures and the use of automated
documentation software can facilitate an organization’s ability to maintain accurate
documentation.
 2. Final Inspection

Consumers’ expectations are that they will receive their vehicle back in a serviceable

condition and in a better operational condition than when it was delivered to the

workshop. This expectation requires two (2) critical components:

 A final inspection must be completed by the service technician to ensure that all of

the protective features for the braking system have been refitted is replaced to the

required specifications; and

 A final inspection must be completed by the service technician to ensure that all of

the work that was commenced on the system was completed to workplace, customer

and manufacturers expectations.

 3. Service provision
• There are some tasks that a technician will not carry out frequently.

• It would be unrealistic for a technician to have a detailed knowledge of seldom-

performed procedures.

• In these circumstances, job cards or checklists are very useful as they give a step-
by-step guide to follow whenever the rarely-used procedure needs to be performed.
• The required knowledge is often kept in manuals which may not be easily
accessible.
• However, going through a large manual, possibly in front of a customer, does
nothing for time effectiveness or professional image.
• A job card is also used as the basis of a recording process for the organization.
• In addition to refreshing the process for the technician it will be a list of the
workplace expectations as well.
• It is suggested that the final task on a job card will be to ensure that the equipment
is cleaned for use or storage.
 4. Noting and documenting observations during the service
 The most precise way to document instruction is to create a Running Record, or
virtual transcript, noting what was observed every two minutes.

 Direct observation of behaviors is important for many reasons.

 It is a means of generating hypotheses and new ideas or a means of answering

specific questions.

 Observations also enable us to answer questions about what happens during

repairing.

 For the purpose of these observations, time sampling is used to record engine parts
repairing.

 An observer should attend to all contextual details on the parts of engine repair.

 Observers do not make any assumptions at any time.

 They do not assume that any event is instructionally relevant or irrelevant.

 Observers should avoid biases based on personal preferences or practice.

 That is, when assigned to observe a particular instructional program, observers do

not judge the engine parts or specific activities during repairing.

 Observers must record what kind of an engine part is repaired without making

ongoing judgments about the quality of engine part repairing or the effective use of a

particular technique.

 The observer’s job is to capture what happened, not his or her opinion of what
happened.

 After noting and documenting the observation during the repair every technician
should complete work shop practice schedule documentation.
 Follow these three general principles to develop records and documents:

1. Keep it short and simple. Use bullet points and flow diagrams instead of long

sentences and lengthy paragraphs.

2. Clarity is important. Step-by-step instructions are easily understood.

3. Use a standardized, consistent format. Although different programs may need

different documents and records, using a similar approach will help staff learn

quickly.
 5. Completing and delivering report to appropriate person

Delivery is the process of transporting something/ like reports/ from a source location

to a predefined destination after the work is done. The technician should be prepare a

report and deliver to appropriate person. The reporting Record the work to be done

 Inspect/test the repaired engine accordance with manufacturer procedure

 Record/ capture the problem with the necessary information

 Order the recorded problems /work done in accordance with their damaging area

 Preparing reports have no error/discrepancy

 Deliver reports to appropriate person.

Unit Four: Cleanup work area and maintain equipment
This unit is developed to provide you the necessary information regarding the
following content coverage and topics:

 Waste and scrap materials

 Hazardous goods and substances
 Tools equipment
 Workplace documentation and reporting
This unit will also assist you to attain the learning outcomes stated in the cover
page. Specifically, upon completion of this learning guide, you will be able to:
 Reusing waste and scrap materials
 Safe handling and storage of hazardous goods and substances
 Inspecting and maintain tools equipment
 Workplace documentation and reporting
 4.1 Cleaning and making ready workplace for next work
• Cleaning is not just a measure of respect for the workspace, it also removes

hazards.

• Plan to easily and regularly remove trash and debris. Enforce a strict clean up

policy throughout the workspace.

• Keep work areas tidy as well by minimizing the number of wires running around.

• Extension cords quickly become tripping hazards, and power strips also cause

trouble on the ground or as they tumble erratically on a desktop.

• We suggest you provide access to grounded outlets all along the perimeter of the

room and/or dropped from the ceiling for each workbench.

 4.2 Kinds of Cleaning Solvents
• Solutions are homogeneous mixture of two or more components.
• They can be gaseous, liquid or solid.
• When we speak of a solution, we usually think of a solid dissolved in water.
• While water is the most common solvent, other liquids are frequently employed as
solvents for certain substances for example wax maybe dissolved in gasoline.
• The dissolved material in a solution is termed as solute (e.g. Wax) while the
dissolving medium is called solvent (e.g. Gasoline).
• However, the term can be interchanged depending on which substance is of greater
amount.
• Solvent is a component of a solution that dissolves solute and is usually present in
large proportion or amount.
• It can be classified as polar or non-polar.
• Polar solvents are solvents which dissolve/are soluble in water; while non-polar
solvents are solvents which do not dissolve/are insoluble in water.
• Solvents usually used for cleaning in automotive shops are: water, gasoline,
kerosene, thinner and detergent soap.
• The table below shows the kinds of cleaning solvents based on their solubility in
water.
Cleaning Solubility in Polar Nonpolar
Solvents Water
a. Water Soluble X
b. Gasoline Insoluble X
c. Kerosene Insoluble X
d. Thinner
Insoluble X
e. Detergent soap
Soluble X
 4.3 Properties of Cleaning Solvents

• A useful generalization much quoted is that “Like dissolves like”.

• More specifically, high solubility occurs when the molecules of the solute are

similar in structure and electrical properties to the molecules of the solvent.

• When there is a similarity of electrical properties; e.g. High dipole element between

solute and solvent, the solute-solvent attractions are particularly strong.

• When there is dissimilarity, solute-solvent attractions are weak.

• For this reason, a polar substance such as H2O usually is a good solvent for a polar

substance such as detergent soap but a poor solvent for a non-polar substance such

as gasoline.
 Uses of Cleaning
Solvents
Cleaning Solvents Uses

1. Gasoline It is used to wash oil/greasy tools/equipment.

2. Diesel It is used to wash oil engine, transmission and other parts

of the vehicle.

3. Kerosene It is used to remove dust, grease oil, paint, etc.

4. Thinner It is used to remove spilled paint on the floor, walls and

tools.

5. Soap and water It is used to wash/clean upholstered furniture such as

seats, tables, cabinets, etc.
 4.4 Occupational Health and Safety Practices in Handling Cleaning Solvents

1. A great percentage of eye injury and cuts results from a disregard for the simplest of

rules in handling cleaning solvents.

2. You should never use compressed air to clean your clothes, hands or body.

3. The pressure could cause the cleaning solvents and dirt particles to penetrate your

skin, resulting in infection and /or blood poisoning.

4. Do not use compressed air to clean an object immediately after it has been

removed from a hot cleaning tank.

5. First, rinse the cleaning solvents away with water.

6. Do not use carbon tetrachloride as a cleaning solution.

7. The fumes, when inhaled can cause serious internal injury and possibly result in

death.

8. When steam-cleaning, place the object to be cleaned on a pallet and wear a face

shield and rubber gloves for protection against loose debris.

9. If a job or cleaning task requires the use of gloves, use the appropriate gloves.

10. Do not for instance use welding gloves when removing an object from a hot tank,

or rubber gloves when welding.

11. If you have cut, nicked, or burned yourself, or something has got into your eyes,
report immediately to the first-aid person.
12. Keep all inflammable cleaning solvents in closed tin containers and whenever
possible, store them in a separate area.
 Cleaning procedures

 Clean up every time whenever you leave an area, including sweeping the floor.
 Clean and return all tools to where you got them.
 Use compressed air sparingly; never aim it at another person or use it to clean hair
or clothes.
 Shut off and unplug machines when cleaning, repairing, or oiling.
 Never use a rag near moving machinery.
 Use a brush, hook, or a special tool to remove chips, shavings, etc. From the work
area. Never use the hands.
 Keep fingers clear of the point of operation of machines by using special tools or
devices, such as, push sticks, hooks, pliers, etc.
 Keep the floor around machines clean, dry, and free from trip hazards. Do not
allow chips to accumulate.
 Mop up spills immediately and put a chair or cone over them if they are wet
enough to cause someone to slip.
THE END
•WE THANK YOU !