The easiest way to test the operation of the fuel injectors is to listen for a clicking sound coming from the injectors while the engine is running. This is accomplished using a mechanic's stethoscope, or a long screwdriver. Place the end of the stethoscope or the screwdriver (tip end, not handle) onto the body of the injector. Place the ear pieces of the stethoscope in your ears, or if using a screwdriver, place your ear on top of the handle. 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.
All Injectors Clicking
If all the injectors are clicking, but you have determined that the fuel system is the cause of your driveability problem, continue diagnostics. Make sure that you have checked fuel pump pressure as outlined earlier in this section. An easy way to determine a weak or unproductive cylinder is a cylinder drop test. This is accomplished by removing one spark plug wire at a time, and seeing which cylinder causes the least difference in the idle. The one that causes the least change is the weak cylinder.
If the injectors were all clicking and the ignition system is functioning properly, remove the injector of the suspect cylinder and bench test it. This is accomplished by checking for a spray pattern from the injector itself. Install a fuel supply line to the injector (or rail if the injector is left attached to the rail) and momentarily apply 12 volts DC and a ground to the injector itself; a visible fuel spray should appear. If no spray is achieved, replace the injector and check the running condition of the engine.One or More Injectors Are Not Clicking
If one or more injectors are found to be not operating, 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 tool 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 11-18 ohms.
If the "noid" light does not flash, the injector driver circuit is faulty. Disconnect the negative battery cable. Unplug the "noid" light from the injector connector and also 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 specifications, the injector driver inside the PCM is faulty and replacement of the PCM will be necessary.
REMOVAL & INSTALLATION
- Properly relieve fuel system pressure, as outlined earlier in this section.
- Disconnect the negative battery cable.
- On the 3.1L engine, remove the upper intake manifold, as outlined in of this guide.
- As outlined later in this section, remove the fuel rail.
- Unfasten and discard the injector retaining clip, then remove the injector assembly. Remove and discard the O-rings from each end of the injector.
- Lubricate new O-rings with clean engine oil, the install on the injector.
- Position a new injector retaining clip on the injector.
- Install the injector assembly into the fuel rail injector socket, with the electrical connector facing inward toward the manifold. Push the socket in far enough to engage the retainer clip with the groove on the rail.
- Install the fuel rail assembly, as outlined later in this section.
- On the 3.1L engine, install the upper intake manifold.
- Connect the negative battery cable.