WARNING
Stay clear of all moving engine parts. Do not wear dangling jewelry or loose clothes. Keep power tool cords or other items that might get caught in a moving part away from fan and pulleys. Also, do not work on an open fuel system around open flames, welders, or any device that can cause a spark.
Checking fuel injector operation with the engine running is as simple as listening for a clicking sound coming from the injectors. Use a mechanic’s stethoscope, or a section of rubber hose. Place the end of the stethoscope or the rubber hose onto the body of the injector. Place the stethoscope in your ears, or place the end of the hose against your ear. An audible clicking noise should be heard; this is the solenoid operating. If the injector makes this noise, the injector driver circuit and computer are operating as designed. Continue testing all the injectors this way.
If you've determined that all injectors are clicking, but the problem is the fuel system continue diagnostics. Make sure that you have checked fuel pump pressure as outlined. An easy way to determine a weak or unproductive cylinder is a cylinder drop test. This is accomplished by cancelling one cylinder at a time, and seeing which cylinder causes the least difference in the idle. The cylinder(s) that causes the least change is the weak cylinder(s).
If the injectors were all clicking and the ignition system is functioning properly, remove the injector of the suspect cylinder and have it bench tested. This is accomplished by checking for a spray pattern from the injector itself. The injectors are placed in a device that applies an electrical signal to the injector and a supply of pressurized solvent (not fuel) to check the spray pattern. If no spray is achieved, replace the injector and check the engine performance.
| Unplug the fuel injector connector
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| Probe the two terminals of a fuel injector to check resistance
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| Plug the correct "noid" light directly into the injector harness connector
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| If the correct "noid" light flashes while the engine is running, the injector driver circuit inside the PCM is working
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If one or more injectors are found to be inoperative, testing the injector driver circuit and computer can be accomplished using a "noid" light. First, with the engine not running and the ignition key in the OFF position, remove the connector from the injector you plan to test, then plug the "noid" light into the injector connector. Start the engine and the "noid" light should flash, signaling that the injector driver circuit is working. If the "noid" light flashes, but the injector does not click when plugged in, test the injector’s resistance. Resistance should be between 13.8-15.2 Ohms. Repeat this procedure on each injector, noting which cylinder(s) are faulty.
If the "noid" light does not flash, the injector driver circuit is faulty. Shut OFF the engine, and then disconnect the negative battery cable. Unplug the "noid" light from the injector connector and unplug the PCM. Check the harness between the appropriate pins on the harness side of the PCM connector and the injector connector. Resistance should be less than 5.0 ohms; if not, repair the circuit. If resistance is within specification, the injector driver inside the PCM is faulty. Replace the PCM.
