Fuel Injector: Testing and Inspection

CIRCUIT DIAGRAM











USING SCAN TOOL





HARNESS TEST

Oscilloscope Pattern:

Fuel Injector Circuit:

Oscilloscope Pattern:

OSCILLOSCOPE TEST
1. Run the engine until it reaches operating temperature. Maintain idle speed for testing.
2. Connect the scope pick-up probe to the test points shown in the system schematic. Compare the scope pattern to the image shown. If scope pattern is not as depicted in image, continue with the rest of the test procedures before replacing the assembly.

Operational Test:

FUNCTIONAL TEST
1. Using a stethoscope, check the operational sound (tick) made by the injectors (one at a time) during idle or cranking. Check that the sound is produced at shorter intervals as the engine speed increases.

NOTE: Other injectors may produce sound as they operate even if the injector being tested does not operate. Ensure that the sound from an adjacent injector is not being transmitted along the delivery pipe to an inoperative injector.

Resistance Test:

INJECTOR RESISTANCE
1. Disconnect the connector for the injector.
2. Measure the resistance between the terminals.

Resistance: 13 - 16 ohms at 20°C (68°F)

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

2. If the injectors do not operate when the engine is cranked check the following:
1. Faulty power supply or ground to the engine control module.
2. Faulty MFI control relay.
3. Faulty crankshaft position sensor or camshaft position sensor.

3. if there is any cylinder whose idle state remains unchanged when the fuel injectors are cut out one after the other during idling check for the following items on that cylinder.
1. Injector and harness.
2. Spark plug and wire.
3. Compression.

4. If the injection system is ok but the injection drive time is out of specification, check the following items:
1. Poor combustion in the cylinder (faulty spark plugs, ignition coil, compression, etc.)
2. Egr valve not seating.