GM Cavalier/Sunfire 1995-2000 Repair Guide

Bottom Feed Port Fuel Injectors

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TESTING



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.


CAUTION
Be extremely careful while working on an operating engine, make sure you have no dangling jewelry, extremely loose clothes, power tool cords or other items that might get caught in a moving part of the engine.

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

See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Unplug the fuel injector connector



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Fig. Fig. 2: Plug the correct noid light directly into the injector harness connector



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Fig. Fig. 3: If the correct noid light flashes while the engine is running, the injector driver circuit inside the PCM is working



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Fig. Fig. 4: Probe the two terminals of a fuel injector to check it's resistance

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



See Figures 5, 6, 7, 8, 9, 10 and 11


WARNING
Any time the injectors are removed for service, always remove the fuel pressure regulator to drain excess fuel, and prevent fuel from entering the engine cylinders. Flooded cylinders could result in engine damage.



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Fig. Fig. 5: Cross-section view of a bottom feed fuel injector



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Fig. Fig. 6: Remove the fuel injector retainer bracket attaching screws (arrows)



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Fig. Fig. 7: Remove the bracket by carefully sliding it off to clear the injector slots



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Fig. Fig. 8: Unplug the injector electrical connectors



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Fig. Fig. 9: Remove the fuel injectors from the lower intake manifold assembly



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Fig. Fig. 10: Remove the injector O-rings and discard them



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Fig. Fig. 11: You may need to use a pick to remove the O-rings as the are sometimes hard to get a hold of

  1. Relieve the fuel system pressure as outlined earlier.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the upper manifold assembly.
  6.  


CAUTION
To reduce the chance of personal injury, cover the fuel line connections with a shop towel, when disconnecting.

  1. Disconnect the fuel return line retaining bracket nut and move the return line away from the regulator.
  2.  
  3. Remove the pressure regulator assembly.
  4.  


WARNING
Do not try to remove the injectors by lifting up on the injector retaining bracket while the injectors are still installed in the in the bracket slots or damage to the bracket and/or injectors could result. Do not attempt to remove the bracket without first removing the pressure regulator.

  1. Remove the injector retainer bracket attaching screws and carefully slide the bracket off to clear the injector slots and regulator.
  2.  
  3. Detach the injector electrical connectors.
  4.  
  5. Remove the fuel injector(s), then remove and discard the O-ring seals.
  6.  


CAUTION
To reduce the risk fire and personal injury, make sure that the lower (small) O-ring of each injector does not remain in the lower manifold. If the O-ring is not removed with the injector, the replacement injector, with new O-rings, will not seat properly in the injector socket and could cause a fuel leak.

  1. Cover the injector sockets to prevent dirt from entering the opening.
  2.  

Each injector is calibrated with a different flow rate so be sure to replace the injector with the identical part numbers.

To install:
  1. Lubricate the new injector O-ring seals with clean engine oil and install on the injector assembly.
  2.  
  3. Install the injector assembly into the lower manifold injector socket, with the electrical connectors facing inward.
  4.  
  5. Carefully position the injector retainer bracket so that the injector retaining slots and regulator are aligned with the bracket slots.
  6.  
  7. Attach the injector electrical connectors.
  8.  
  9. Install the pressure regulator assembly.
  10.  
  11. Install the injector retainer bracket retaining screws, coated with thread locking material and tighten to 31 inch lbs. (3.5 Nm).
  12.  
  13. Install the accelerator cable bracket with the attaching bolts/nuts finger-tight at this time.
  14.  


WARNING
The accelerator bracket must be aligned with the accelerator cam to prevent cable wear, which could result in cable breakage.

  1. Align the accelerator bracket as follows:
    1. Place a steel rule across the bore of the throttle body, with one end in contact with the accelerator bracket.
    2.  
    3. Adjust the accelerator bracket to obtain a 25 / 64 in. (9-11mm) gap between the bracket and the throttle body.
    4.  
    5. Tighten the top bolt first and tighten all bolts/nuts to 18 ft. lbs. (25 Nm).
    6.  

  2.  
  3. Tighten the fuel filer cap.
  4.  
  5. Connect the negative battery cable and turn the ignition ON for 2 seconds, OFF for 10 seconds, then ON and check for fuel leaks.
  6.  
  7. Install the air intake duct.
  8.  

 
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