Devices that allow the computer to do
work and alter the operation of other
components
Actuator
Classifications
Actuators can be grouped into the
following categories:
solenoid
relay
servo motor
display device
control module
Actuator Operation
When the computer turns on an
actuator, it normally provides the
device with a ground circuit
Current can then operate the actuator
Solenoid Operation
Computer grounds the solenoid circuit
A magnetic field moves the plunger
mounted in the solenoid windings
Plunger movement is used to operate a
device
fuel injectors, vacuum valves, idle speed
control valve, door locks, etc.
Actuators
Common actuators used on modern
vehicles include:
Fuel injector
solenoid valve that controls fuel flow
Fuel pump
electric motor-driven pump
Actuators
Idle air solenoid
controls airflow into the engine to control
idle speed
EGR solenoids
open and close small ports to control
exhaust gas flow back into the engine
Actuators
Ignition coil
changes low voltage into high voltage
that operates the spark plugs
Ignition module
uses computer signals to control the
operation of the ignition coils
Fuel system
Fuel system components
Fuel pump
In-tank type
In-line type
Fuel filter
Pressure regulator
Pulsation damper
Injectors
Fuel pump
Fuel pump
Fuel pump control
On-off control by engine ECU
Pump control..
On-off control by fuel pump switch operated
by vane type air flow meter
On-off control with speed control
Pressure regulator
Regulates the fuel pressure to the
injectors according to intake manifold
pressure
Pulsation damper
Absorbs slight variation in pressure due
to injection by means of a diaphragm
Pulsation damper
Fuel injector
Is an electromagnetically-operated
nozzle which injects fuel in accordance
with signals from ECU
Injector..
Depending on their resistance value
Injectors are divided in to two;
High resistance type
Low resistance type
Electrical circuitry of injectors
High resistance type
Electrical circuitry....
Low resistance type
Cold start injector
Injects additional fuel during cranking
when the coolant temperature is low
It is controlled by cold start time switch
or ECU
Electrical circuitry of cold start
injector and its time switch
Electrical circuitry.....
Types of fuel injection
methods
Simultaneous fuel injection
Group injection
Sequential fuel injection (SEFI)
Cylinder individual fuel injection (CIFI)
Injection method..
Simultaneous
1. All injectors inject at the same time
2. half of the required fuel is injected in each crankshaft
rotation
Injection method..
Group injection
1. It can be groups of 2,3,4..
2. Each group injects the required amount of fuel once every
two complete rotation of crankshaft
Injection method..
Sequential
Fuel is injected in the same order as the firing sequence
Fuel injection duration and
injection timing control
ECU calculates the basic fuel injection
duration in accordance with two
signals:
1. Amount of air taken to the cylinder
2. Engine speed
D
U
R
I
N
G
S
T
A
R
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G
Injector pulse width
Self induced
Pick voltage
On time (pulse width)
Idle speed control (ISC)
The ISC system controls the idle speed by
adjusting the volume of air allowed to by-
pass the closed throttle valve in accordance
with signals from the ECU.
There are four types of ISC valve:
1. Duty control air control valve
2. Rotary solenoid type
3. Stepper motor type
4. On-off control Vacuum switching valve (reading
assignment)
Duty control type
It regulates the volume of air by-passing the
closed throttle valve by opening and closing
an air by-pass
Valve opening time is a function of a duty
cycle signal received from the ECU
Is incapable of flowing large volumes of air;
therefore, a separate mechanical air valve is
used
Duty .......
Duty control..
Duty ratio Ontime
ontime offtime
Rotary solenoid type
Air volume control is done by means of
a movable rotary valve which blocks or
exposes the air bypass port based on
signals received from the ECU.
Is capable of large air volume, so no
need of using mechanical air valve.
Rotary type..
Stepper motor type
regulates engine speed by means of a
stepper motor and pintle valve which
controls the volume of air by-passing
the closed throttle valve
is capable of controlling large volumes
of air, so it is not used in combination
with a mechanical air valve.
Stepper motor...
Stepper motor...
Neutral start switch
