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Home >> Pontiac >> 2003 >> Vibe Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - System & Component Testing >> Fuel Systems >> Fuel System Diagnosis >> Diagnostic Procedures
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Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 1.8L VIBE article.
  2. Turn ignition switch to OFF position. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  procedure. Install a fuel pressure gauge. See FUEL GAUGE under FUEL SYSTEMS in REMOVAL & INSTALLATION - 1.8L VIBE article. Connect scan tool. Turn ignition switch to RUN position, engine OFF. Select FUEL PUMP in ENGINE OUTPUT CONTROLS menu of the scan tool. Using the scan tool, turn the fuel pump ON. Observe the fuel pressure indicated by the fuel pressure gauge with the fuel pump running. Is any fuel pressure indicated? If yes, go to next step. If no, go to step  5 .
  3. Using the scan tool, turn the fuel pump ON. Observe fuel pressure indicated by the fuel pressure gauge with the fuel pump running. Is fuel pressure 44-50 psi (301-347 kPa)? If yes, go to step  12 . If no, go to next step.
  4. Is the fuel pressure more than 50 psi (347 kPa)? If yes, go to step  22 . If no, go to next step.
  5. Was the circuit opening relay diagnostic performed? If yes, go to step  24 . If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS  .
  6. Remove the bottom cushion of the rear seat to gain access to the fuel sender assembly access panel. Turn ignition switch to RUN position, engine OFF. Place a listening device against the access panel. Command the fuel pump ON, using the scan tool. Listen for audible fuel pump operation. The fuel pump should have a smooth and steady low humming sound. Is the fuel pump operating as described? If yes, go to next step. If no, go to step  24 .
  7. Measure the resistance of the fuel pump, with a DMM. Is the fuel pump resistance 0.2-3.0 ohms at 68°F (20°C)? If yes, go to next step. If no, go to step  24 .
  8. Visually and physically check the fuel feed pipe for kinks, cracks, incorrect routing or restrictions. Repair as necessary. Was a repair necessary? If yes, go to step  25 . If no, go to next step.
  9. Remove the fuel sender assembly. Visually and physically check the fuel pump strainer for plugging or restriction. Was the fuel pump strainer found to be plugged? If yes, go to step  23 . If no, go to next step.
  10. Visually and physically inspect the seals and the "O" rings between the fuel pump, the fuel filter, and the fuel pressure regulator for cracks, splits, deformation or missing components. Repair as necessary. Was a repair necessary? If yes, go to step  25 . If no, go to next step.
  11. Check the fuel filter for a restriction. Replace the fuel filter, if necessary. Was the fuel filter replaced? If yes, go to step  25 . If no, go to step  22 .
  12. Using the scan tool, turn the fuel pump ON. Wait for the fuel pressure to stabilize. Turn the fuel pump OFF. Monitor the fuel pressure on the fuel gauge. Does the fuel pressure remain equal to or more than 21 psi (147 kPa) for 5 minutes after the fuel pump is turned OFF? If yes, go to next step. If no, go to step  17 .
  13. Does the fuel pressure decrease during acceleration, cruise, or hard cornering? If yes, go to next step. If no, go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 1.8L VIBE article.
  14. Visually and physically inspect the fuel filter and fuel feed pipe for restrictions. Was a restriction found? If yes, go to next step. If no, go to step  16 .
  15. Repair the restriction as necessary. After repair, go to step  25 .
  16. Visually and physically inspect for any of the following conditions:
    • A restricted fuel pump strainer.
    • An incorrectly positioned fuel pump pick-up.
    • The incorrect fuel pump.
    • A loose or missing fuel pump or tank baffle.

    Repair as necessary. Was a repair necessary? If yes, go to step  25 . If no, go to step  24 .

  17. Turn the fuel pump ON using the scan tool. Pinch off the fuel pressure gauge adapter hose on the fuel tank side, while monitoring the fuel gauge. Turn the fuel pump OFF. Does the fuel pressure remain equal to or more than 21 psi (147 kPa) for 5 minutes after the fuel pump is turned OFF? If yes, go to step  19 . If no, go to next step.
  18. Check for a fuel leak at the base of the fuel injectors, at the fuel injectors and at the fuel rail. Repair as necessary. Was a repair necessary? If yes, go to step  25 . If no, go to step  20 .
  19. Check the fuel feed pipe for leaks. Repair as necessary. Was a repair necessary? If yes, go to step  25 . If no go to next step.
  20. Remove the fuel sender assembly. Visually and physically check the seals and "O" rings between the fuel pump, the fuel filter, and the fuel pressure regulator for the following conditions:
    • Any cracks.
    • Any splits.
    • Any deformation.
    • Any missing components.

    Inspect the entire fuel pump electrical circuit. Verify battery voltage at the fuel pump connector and less than 5.0 ohms to ground. Repair as necessary. Was a repair necessary? If yes, go to step  25 . If no, go to next step.

  21. Check the fuel filter and the fuel pump for cracks or a leaking seam. Replace as necessary. Was a component replacement necessary? If yes, go to step  25 . If no, go to next step.
  22. Replace the fuel pressure regulator. See FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL & INSTALLATION - VIBE article. Attempt to start and run the engine. Monitor the fuel pressure gauge while the engine is running. Is the fuel pressure 44-50 psi (301-347 kPa)? If yes, go to step  25 . If no, go to next step.
  23. Replace the fuel pump strainer. Inspect the fuel system for the cause of the plugged fuel pump strainer. Repair as necessary. After repair, go to next step.
  24. Replace the fuel pump. See FUEL PUMP under FUEL SYSTEMS in REMOVAL & INSTALLATION - VIBE article. After repair, go to next step.
  25. Attempt to start and run the engine. Monitor the fuel pressure gauge while the engine is running. Is the fuel pressure 44-50 psi (301-347 kPa)? If yes, system is okay at this time. If no, go to step  2 .
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