1. Actuators Topics covered in this presentation:
Fuel Injector and Mixture/shutoff Solenoids
IAC Solenoids and Relays
Fuel Pumps
ClassAct SRS enabled.

2. Introduction Three basic actuator types: Solenoid. Relay. Motor.
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3. Question 1
Which of the following is NOT a basic type of actuator usually controlled by an ECU?
A) DC Motor
B) Lamp
C) Solenoid
Correct Answer = B
D) Relay

4. Electronic Fuel Injector Operation
Fuel injector contains a solenoid coil.
Coil energized, needle valve lifts from nozzle, fuel sprayed into engine.
Coil not energized, needle valve seals nozzle and no fuel flows.
Injectors are precise and efficient.
Needle valve
Electrical connector
Fuel filter
Fuel in
Spring
Armature
Nozzle / jet
Solenoid coil
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5. Question 2
These are the stages of electronic fuel injection operation:
1. When a voltage is applied to the coil it is energized.
2. When the coil is energized the armature moves out of the coil.
3. The fuel flows into the engine.
4. The armature is returned to its original position by a spring when it is no longer energized.
Which one is incorrectly described?
A) 1
C) 3
Correct Answer = B
B) 2
D) 4

6. Injector Pulse Width
ECU controls injector pulse width (injector opening time).
Pulse width determined from:
1. Air volume.
4. Throttle position.
2. Engine temperature.
5. Exhaust oxygen content.
3. Air temperature.
Timing pulses
(engine speed)
Cyl. 1
Cyl. 2
Cyl. 3
Cyl. 4
Pulse shaper
Frequency divider 1 2 3 4 5
Injector pulse width
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7. Question 3
Which of the following does NOT control injector pulse width?
A) Fuel pressure
B) Engine temperature
C) Air volume
Correct Answer = A
D) Throttle position

8. Idle Air Control (IAC) Valve
Operated by solenoid or stepper motor.
ECU
IAC valve
Throttle valve
Air in
Solenoid coil
Used to control idle speed of engine, by allowing air to bypass throttle valve.
ECU determines the amount of bypass air.
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9. Question 4
Which of the following statements about the Idle air control (IAC) is true?
A) The IAC controls the throttle valve
B) The IAC controls the amount of air bypassing the throttle valve
C) The IAC controls the top speed of the engine
Correct Answer = B
D) The IAC senses whether the engine is idling correctly

10. Fuel mixture control solenoid
Computer Controlled Carburettors
ECU monitors sensors.
ECU O2
ECT
MAP
Manifold
Controls mixture solenoid to change air/fuel mixture.
When solenoid energized, fuel flow blocked.
Main discharge
Fuel mixture control solenoid
Energized
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11. Computer Controlled Carburettors
Duty cycle signal from ECU switches solenoid on and off.
ECU
Fuel mixture
control solenoid
Main
discharge
Efficient mixture
Rich mixture
Lean mixture
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12. Fuel Shut-Off Solenoid
Fuel shut-off solenoid used when switching off or decelerating.
Shut-off
solenoid
Inlet Manifold
Carburettor
ECU
Main fuel
metering passage
Blocks fuel passages and stops fuel leaks and drips.
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13. Question 5
With a computer controlled carburettor, when is the fuel flow blocked?
A) When the sensor monitors the flow
B) When the mixture is energized
C) When the air supply is insufficient
Correct Answer = D
D) When the fuel mixture control solenoid is energized

14. Electric Fuel Pumps Transfers pressurized fuel from tank to engine.
Pump either in fuel tank, or between fuel tank and engine.
Both types are used
in some fuel systems.
Inertia switch stops flow in the event of an accident.
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15. Summary You should be aware of:
Fuel Injector and Mixture/shutoff Solenoids
IAC Solenoids and Relays
Fuel Pumps
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