Fuel Injector Circuit Tests
- Check Fuel Injector Operation - Using a stethoscope, ensure injector operating sound (clicking) is present while engine is cranking. If operating sounds are not heard, go to next step. If operating sounds are heard, verify fuel pressure. See FUEL PRESSURE under FUEL SYSTEM.
- Check ECM Output Signal - Turn ignition on. Measure voltage between ECM connector terminals and ground. See ECM OUTPUT SIGNAL & FUEL INJECTION HARNESS IDENTIFICATION table. If voltage is more than 10 volts go to next step. If voltage is less than 10 volts, go to step 4).
- Check Harness Between ECM Connector & Fuel Injector
- Turn ignition off. Disconnect connector from fuel injector. Turn ignition on. Backprobe ECM connector to measure voltage between listed ECM connector terminals and ground. See ECM OUTPUT SIGNAL & FUEL INJECTION HARNESS IDENTIFICATION
table. If voltage is more than 10 volts, repair short in harness between ECM and fuel injector. If voltage is less than 10 volts, turn ignition off. Measure resistance between fuel injector terminals No. 1 and 2. See Fig 1
. If resistance is less than one ohm, replace fuel injector and ECM. If resistance is more than one ohm, inspect ECM connector for poor contact. If connector is okay, replace ECM.ECM OUTPUT SIGNAL & FUEL INJECTION HARNESS IDENTIFICATION
ECM Terminal No. Engine Cylinder No. 96 1 70 2 44 3 16 4 43 5 15 6 - Check Resistance Between Fuel Injectors & ECM Connector - Turn ignition off. Disconnect connector from fuel injector on faulty cylinder(s). Measure resistance between fuel injector connector terminal No. 1 and ground. If resistance is less than 10 ohms, repair short to ground in harness between fuel injector and ECM connector. If resistance is more than 10 ohms, measure resistance of each harness circuit between ECM connector terminal and fuel injector connector terminal. If resistance is less than one ohm, go to step 5). If resistance is more than one ohm, repair open in harness between ECM and fuel injector connector.
- Check Fuel Injector - Measure resistance between fuel injector terminals No. 1 and 2. Resistance should be between 5 and 20 ohms. If not as specified, replace fuel injector. If resistance is as specified, turn ignition on. Measure voltage between fuel injector terminals No. 2 and ground. If voltage is more than 10 volts, repair poor contact in connectors. If voltage is less than 10 volts, repair harness and connectors. See appropriate wiring diagram in WIRING DIAGRAMS article.