Fuel Injector: Testing and Inspection

INJECTORS





OPERATION
^ The injector is an injection nozzle with a solenoid valve which injects fuel according to the injection signal coming from the engine control unit.

^ The injector has a fixed nozzle opening area and the fuel pressure against manifold inside pressure is regulated to a fixed level. Theretore, the volume of fuel injected by the injector is determined by the time during which the needle valve is open, namely, by the time during which the solenoid coil is energized.

^ The battery voltage is applied through the control relay to this injector. When the engine control unit turns ON the power transistor in the unit, the solenoid coil is energized to open the injector valve, which then injects fuel.


TROUBLESHOOTING HINTS
Hint 1: If the engine is hard to start when hot, check fuel pressure and check the injector tor leaks.

Hint 2: If the injector does not when the engine that is hard to start is cranked, the following as well as the injector itself may be responsible.
(1) Faulty power supply circuit to the engine control unit, faulty ground circuit
(2) Faulty control relay
(3) Faulty crank angle sensor, top dead center sensor

Hint 3: If there is any cylinder whose idle state remains unchanged when the fuel injection of injectors is cut one after another during idling, make following checks about such cylinder.
(1) Injector and harness check
(2) Ignition plug and high tension cable check
(3) Compression pressure check

Hint 4: If the injector harness and individual part checks have resulted normal but the injector drive time is out of specification, the following troubles are suspected.
(1) Poor combustion in the cylinder (faulty ignition plug, ignition coil, compression pressure, etc.)
(2) Loose EGR valve seating
(3) High engine resistance


INSPECTION
Using Multi-use Tester





Using Oscilloscope
(1) Run the engine at idle speed.





(2) Connect the probe to the oscilloscope pick-up point as shown in the circuit diagram, and check the waveform at the drive side ot each injector.

HARNESS INSPECTION





ACTUATOR INSPECTION

Checking Operation Sound
- Using a sound scope, check the operation sound ("chi-chi-chi") of injectors during idling or during cranking.
- Check that as the rotating speed increases, the frequency of the operating sound also increases.

Caution: Note that even if the injector you are checking is not operating, you will hear the operating sound of the other injectors.

NOTE: If no operating sound is heard from the injector that is being checked, check the injector drive circuit. If there is nothing wrong with the circuit, a defective injector or engine control unit is suspected.

Measurement of Resistance between Terminals
(1) Remove the injector connector.
(2) Measure the resistance between terminals.

Standard value: 13 - 16 Ohms [at 20°C (68°F)]

(3) Install the injector connector.