GM Lumina/Silhouette/Transport APVs 1990-1999 Repair Guide

Fuel Injectors

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The SFI fuel injector is a solenoid-operated device controlled by the PCM. The PCM energizes the solenoid, which opens a valve to allow fuel delivery.

See Figures 1, 2 and 3

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Fig. Fig. 1: This is a ported fuel injector and its two O-rings and retaining clip

Fuel is injected, under pressure, in a conical spray pattern at the opening of the intake valve. Excess fuel not used by the injectors passes through the pressure regulator before being returned to the fuel tank.



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Fig. Fig. 2: This is a schematic of a typical ported fuel injector



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Fig. Fig. 3: Typical fuel rail assembly for a V-6 engine shown

The fuel injector is serviced as a complete assembly only and should never be immersed in any type of cleaner. Support the fuel rail to avoid damaging other components while removing the injector. Be sure to note that different injectors are calibrated for different flow rates. When replacing fuel injectors, be sure to get an exact replacement.

REMOVAL AND INSTALLATION



The fuel injector is serviced as a complete assembly only. If the injector fails the leak test, the engine oil may be contaminated with fuel. It would be recommended to change the oil and filter.

  1. Properly relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the fuel rail from the vehicle; remove the fuel feed and return pipes from the fuel rail.
  6.  
  7. Remove the fuel injector retaining clips, separate the injector from the fuel rail.
  8.  

When ordering new fuel injectors, be sure to order the correct injector for the applications being serviced. The fuel injector lower O-ring (brown) uses a nylon collar, called the O-ring backup, to properly position the O-ring on the injector. Be sure to reinstall the O-ring backup, or the sealing O-ring may move on the injector when installing the fuel rail and result in a possible vacuum leak and driveability complaints will occur.

See Figures 4 through 11

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Fig. Fig. 4: Unplug the injector harness from the injector



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Fig. Fig. 5: Remove the fuel rail hold-down bolts ...



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Fig. Fig. 6: ... which can be difficult to see under layers of accumulated dirt



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Fig. Fig. 7: Using an even force, raise the fuel rail, pulling the injectors from their mounting holes (arrows) in the manifold



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Fig. Fig. 8: Using a small pry tool, pry the injector lock from the injector



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Fig. Fig. 9: Gently pull the injector from the rail. A slight twisting motion may help ease removal



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Fig. Fig. 10: The injector O-rings can be removed easily



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Fig. Fig. 11: Injector flow is defined by the application. Installing the wrong one will cause driveability problems, always use direct replacement parts

To install:
  1. Install the new injectors using new O-rings. Coat the O-rings with clean engine oil.
  2.  
  3. Install the injector retaining clips.
  4.  
  5. Install the fuel rail, injectors are retained by the fuel rail.
  6.  
  7. Plug in the electrical connectors to the injectors.
  8.  

TESTING



The injector circuit can be can be tested by installing a "noid light", into the injector electrical harness connector. The light confirms a voltage feed when it flashes, as though the injector was firing.

  1. Start the engine and listen to each fuel injector individually for a clicking sound.
  2.  
  3. Turn the engine OFF and detach the electrical connector from the injector that did not have a clicking sound.
  4.  

See Figure 12

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Fig. Fig. 12: Use an ohmmeter to check injector resistance. Compare readings with a known good injector

  1. Check the injector for continuity across the terminals. Compare the injector the resistance value to a known good injector. The readings should be similar, if so proceed to the next test. If readings differ greatly, replace the injector.
  2.  
  3. Check between each injector terminal and ground. If continuity exists, replace the injector.
  4.  
  5. Detach the fuel injector connector and connect a noid light to the wiring harness connector. Crank the engine, while observing the light. Perform this test on at least two injectors before proceeding. If the light does not flash, check the injector power supply and ground control circuitry. If the light flashes, proceed to the next step.
  6.  
  7. If the light flashes remove the fuel rail from the engine and following the procedure given, check the injector operation.
    1. Using mechanic's wire, secure the injector to the fuel rail.
    2.  
    3. Place a clear plastic container around each injector.
    4.  

  8.  


CAUTION
Before performing this test, all fuel safety precaution must be followed. Make certain the container is approved to handle fuel and is securely positioned around the injector. Do not use a glass container. Glass containers can be easily damaged, resulting in a serious fire hazard.

    1. With the help of an assistant or using a remote starter button, crank the engine for 15 seconds while observing the injector operation. The injector should produce a cone shaped spray pattern and all containers should contain equal amounts of fuel.
    2.  
    3. Once the cranking test is complete, leave the fuel rail pressurized and observe the injectors for leakage.
    4.  


  1. Replace any injector that leaks or fails to provide a good spray pattern.
  2.  

 
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