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

Fuel Pump

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There are two different electric fuel pumps used:



A medium pressure twin turbine pump for vehicles equipped with Throttle Body Injection (TBI).
 
A high pressure roller vane pump for vehicles equipped with Sequential Fuel Injection (SFI).
 

See Figure 1

Click image to see an enlarged view

Fig. Fig. 1: View of the fuel pump assembly and related components

The fuel pump is mounted to the fuel sender assembly inside the fuel tank. The fuel is pumped to the engine at a specified flow and pressure by the fuel pump. Excess fuel is returned to the fuel tank by the return pipe. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers.


CAUTION
When working on or near the fuel tank, be sure to observe the information molded on the bottom of the tank.

Removal & Installation



  1. Disconnect the negative battery cable.
  2.  
  3. Properly relieve the fuel system pressure.
  4.  

See Figure 2

Click image to see an enlarged view

Fig. Fig. 2: Exploded view of the fuel pump-to-tank mounting components

  1. Drain and remove the fuel tank.
  2.  
  3. Remove the fuel sender assembly.
  4.  
  5. Disassemble the fuel pump strainer and the fuel pump: Note the position of the strainer in relation to the pump.
  6.  

See Figure 3

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Fig. Fig. 3: Remove the fuel tank locking ring with a non-sparking (brass) punch.

  1. Support the fuel pump in one hand, and grab the strainer in the other hand.
    1. Rotate strainer in one direction and pull off pump. Discard strainer.
    2.  

  2.  

See Figure 4

Click image to see an enlarged view

Fig. Fig. 4: Exploded view of the fuel pump components

    1. Remove deflector.
    2.  


  1. Disconnect the fuel pump electrical connector.
  2.  
  3. Loosen the two connecting clamps, if equipped.
  4.  
  5. Place the fuel sender assembly upside down on the work bench.
    1. Pull the fuel pump downward to remove it from the mounting bracket, then tilt the pump outward and remove it from the connecting hose or the fuel pulse dampener.
    2.  

  6.  
  7. It is recommended to replace the hose and clamps, if equipped.
  8.  


CAUTION
Do not run the pump unless submerged in fuel

To install:
  1. Push the fuel pump assembly into the attaching hose. Attach the pump electrical wires and fasten the hose clamps to the attaching hose and around the pump body, where equipped.
  2.  
  3. Place the fuel tank sender and pump assembly into the fuel tank. Use a new O-ring seal during assembly.
  4.  

TESTING



See Figure 5

Click image to see an enlarged view

Fig. Fig. 5: Schematic for hooking up a fuel pressure test gauge to the fuel system-TBI shown, SFI similar

  1. Properly relieve the fuel system pressure and install a pressure test gauge according to the tool manufacturers instructions.
  2.  
  3. Turn the ignition switch to the ON position for 3 seconds, then turn to the OFF position for 5 seconds. Repeat this procedure two or three times to pressurize the system. Again turn the switch to the ON position.
    1. On TBI equipped vehicles, the gauge should read a static pressure of between 9 and 13 psi (62-89kPa)
    2.  
    3. On SFI equipped vehicles, the gauge should read a static pressure of between 41 and 47 psi (248-325kPa)
    4.  
    5. If not, check for a clogged fuel filter, a kinked fuel line, or an inoperative fuel pump.
    6.  

  4.  
  5. On TBI equipped vehicles, the fuel pressure will drop after the fuel pump stops running due to a controlled bleed in the fuel system. Use of the fuel pressure gauge will determine if the fuel system pressure is enough for the engine to start and run.
  6.  
  7. No fuel spray from the injector indicates a faulty fuel or ignition system or no PCM control of the injector.
  8.  
  9. This test will determine if the ignition control module is not generating the reference pulse or if the wiring or PCM are at fault. By touching and removing a test light to B+ on CKT 430 (purple/white wire from the ignition system), a reference pulse should be generated. If the injector test light blinks, the PCM and wiring are OK.
  10.  

See Figures 6 and 7

Click image to see an enlarged view

Fig. Fig. 6: This chart shows the electrical schematic for the TBI injectors and drivers



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Fig. Fig. 7: Shows the wiring on SFI engines, from the fuel pump relay to the PCM and how the oil pressure sensor can control injector firing.

 
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