LV07k

Salman Shah
Level 3 light vehicle maintenance and repair
Multi point injection system:

a. Fuel injectors are very importing in vehicles as is decreases pollution and makes them more
fuel efficient. The multi point injection system on the back of the open intake valves, this is
known as indirect injection. Problems in a multipoint injection system happen when deposits
coat the valve. This causes the absorption of atomised fuel ending up in an outcome of a
lean fuel mixture. The injector also has quite a specific spray pattern, this varies to the type
system or type of engine. Top feed injectors are included with a fine mesh filter at the top.
side feed injectors have become more common; in the fuel rail fuel is able to flow through
the injector, handling fuel temperature issues.

The fuel starts from the tank where the fuel is stored and is then carried through to the main
pump by the pre pump which pressurises and pumps the fuel to the fuel filter where it is
cleaned and all the gunk stays in the filter then it travels to the fuel rail where the pressure is
held then the fuel travels to the injectors and if the fuel is too high then gets sent back to
fuel tank by the regulator and if it’s not too high then it gets sprayed into the cylinder by the
injectors. The fuel is sent by the injectors when it is commanded by the ecu. The ecu knows
when the fuel should be injected through the crank shaft position sensor and also camshaft
sensor.

Fuel tank:

The fuel tank is the starting point of the fuel in the multi point injection system, it is also where the
fuel is safely stored, so the fuel pump can get fuel from the fuel tank and have it pumped into the
internal combustion chambers. The fuel tank also has a fuel return pipe this is so fuel is sent back to
the fuel tank by the regulator through the return pipe if the pressure is too high.

Fuel return pipe:

Fuel filter:

The purpose of the fuel filter is to cleanse the fuel by removing the rust particles and dirt
from the fuel. Fuel filters are usually cartridges containing filter paper. They are also
commonly found in internal combustion engines. The fuel filter also stops the injectors from
getting clogged and prevents that from creating further faults in the engine.
Fuel rail:

The purpose of the fuel rail is to distribute the fuel to the injectors at a high or low pressure for it to
then be injected into the cylinder.
Air flow mass sensor:
fuel pump
Crank position sensor:
Coolant temperature sensor:
Throttle position sensor :
Injector assembly:

Injectors are opened electromagnetically and closed by the pressure of the spring which acts
on the pantile of the injector.

 Solenoids:
Allows high-pressure generation function and fuel injection performance to be
separated.
 Nozzle:
The nozzle is a fine sprayer that injects fuel into an engine. The fuel is sprayed
usually at high pressure this is to improve the mixing of fuel with air.
 Needle valve:
allows precise regulation of flow.
 Valve spring:
Closes the injector.
 Plunger:
at the point of the injector being is energized, there is an electromagnet which
moves the plunger opening the valve which will allow the pressurized fuel to shoot
out through a tiny nozzle.
 Fuel circulation:
Circulate fuel for fuel to make its way through the injector.
 Fuel inlet:
This supplies the fuel and air mixture to the cylinders. Also, can have a purpose of
being a mount for the carburettor, throttle body and fuel injectors.
 O- ring:
to stop fuel and air from leaking
 Nozzle body:
Hold the injector components.
 Armature:
Converts electrical power to mechanical power.

Furthermore, the electrical systematic process is when the driver turns the key to ignition
and the ecu receives the signal and then sends out a signal to start the pump to pump the
 fuel. So, once ignition is turned on the fuel is carried from the tank to the pump in which it
pressurizes and pumps it to the fuel rail. The crankshaft helps by letting the ecu know what
position the piston is and cam shaft sensor helps to let the ecu know what stroke the pistons
are on.

b. A typical electronic fault in the injection system is a dead fuel pump. This could be the pump,
the pump relay or the wiring circuit. The symptoms for this are difficulty starting, whining
noises or the engine not starting the cause of the engine not starting would be insufficient in
the vehicle. To diagnose this, use a voltmeter and put the probes to the sensor terminals and
if the reading shows 0.4volts or below then it is faulty.

c. Get the information from the customer about why they have asked for the vehicle to
checked. These questions should include: what is it that is concerning you about your
vehicle? When was the last time you got it serviced? When did you first experience the
problem and for how long? The customer would reply and say the engine wouldn’t start and
it stutters. Funnel down the information given to you by the customer to what the fault
could be. Start the car the same way the customer was starting the car if the problem is
what the customer explained then begin the checks on the vehicle. Firstly, inspect the
vehicle by doing simple visual checks to see for any noticeable faults. If you couldn’t see any
visible faults in the vehicle then Next check If there is no fuel and the fuel light is showing
then fill up the vehicle with fuel. If the problem isn’t lack of fuel then check if the injectors
are spraying any fuel in the system by cranking the engine and using a stethoscope to listen
if the injectors are firing. If that’s all fine then next check the resistance of the injector by
using an ohmmeter and removing the leads connecting to the injectors.

d. check if the injectors are spraying any fuel in the system by cranking the engine and using a
stethoscope to listen if the injectors are firing. If that’s all fine then next check the resistance
of the injector by using an ohmmeter and removing the leads connecting to the injectors.
The resistance should show 3ohms. Check if the relay was holding any pressure, do this by
using a pressure gauge the pressure should be about 30bar once ignition is turned on and
leave the ignition on to see if the pressure drops.
e. Start off by checking if the injectors were spraying. No fuel is being supplied then check the
pressure in the fuel rail and no pressure is being created then go back to the pump and
check the resistance if the voltage was being supplied to the pump for that use ohm meter
for resistance and voltmeter for voltage to the pump if there was no voltage coming
through, this would lead to the conclusion the fault is in the relay. Find out what type of
relay it is then next test the relay by checking the resistance with an ohm metre. And to fix
the problem replace the relay with a new one correct to the manufacturer’s specification.
Start the vehicle again the same way the customer did to see if the problem is fixed. If the
problem is fixed take the car for a test drive to finalise the repair and confirm everything is
working how it should. Once all these checks are done and the problem is rectified and the
car is working how it should be then pack all tools and equipment used back into their
original location where they belong in.