- Relieve the fuel system pressure. Please refer to Relieving Fuel System Pressure for the procedure.
- Disconnect the negative battery cable.
- If removing a right side (rear) fuel injector, remove the upper intake manifold. Please refer to Engine and Engine Overhaul, Engine Mechanical, Intake Manifold, Removal and Installation for the procedure.
- On 1999-00 3.3L engines, if removing a left side (front) fuel injector, disconnect the spark plug wires from the plugs and position them aside. Then, remove the two left breather tube bracket-to-upper intake manifold bolts, disconnect the left breather hose from the left valve cover, and remove the tube.
- Disconnect the fuel injector electrical connector.
- Remove the two fuel injector cap screws. If removing a right side fuel injector, use a screwdriver tip socket to remove the screws. If removing a left side fuel injector, use a screwdriver tip socket on an extension to reach the screws.
- Remove the fuel injector cap, then, using a rocking side-to-side motion, gently pull the injector from the fuel supply manifold.
- The installation is the reverse of removal, but please note the following important steps.
- Before installing a fuel injector, replace the fuel injector grommet, insulator, and O-ring.
- When installing a fuel injector cap, tighten the screws to 26-33 inch lbs. (2.9-3.8 Nm).
- After installation, cycle the ignition switch several times from the OFF to ON positions without starting the engine, allowing five seconds at each position, to build fuel pressure within the system. Check for fuel leaks.
- Start the engine and recheck for fuel leaks. Road test the vehicle and check for proper operation.
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. On 1993-95 vehicles, if an injector is malfunctioning a diagnostic trouble code for the fuel injection circuit or oxygen sensor circuit (due to a rich or lean condition) may be set by the PCM. On 1996-00 vehicles, each cylinder is monitored by the PCM, and a diagnostic trouble code is set for each cylinder if it is weak or misfires. For information on retrieving trouble codes, please refer to Driveability and Emission Controls, Trouble Codes, Reading Codes.
Another 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 a cylinder drop test is performed, it will be necessary to clear the additional diagnostic trouble codes from the PCM memory after repairs are completed. Please refer to Driveability and Emission Controls, Trouble Codes, Clearing Codes for the procedure.
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. The resistance should be 10-14 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.