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Home >> Saturn >> 2003 >> L300 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Fuel Systems >> Fuel System Diagnosis >> System Description
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System Description

The control module enables the fuel pump relay when the ignition switch is turned to ON position. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within 2 seconds if ignition reference pulses cease to be detected and the ignition remains on.

The fuel tank stores the fuel supply. The electric fuel pump supplies fuel through an in-line fuel filter to the fuel injection system. The pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator maintains the correct fuel pressure to the fuel injection system. A separate pipe returns unused fuel to the fuel tank.

  1. If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 3.0L SATURN "L" SERIES article.
    2. NOTE: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic.
  2. Turn ignition on, with engine off. Command the fuel pump relay ON with a scan tool. If the fuel pump operates, go to next step. If fuel pump does not operate, see FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS  .
    3. NOTE: Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.
  3. Turn ignition on, with engine off. Remove the hose from the fuel pressure regulator. Command the fuel pump relay ON with a scan tool. Inspect for a fuel leak from the fuel pressure regulator port. If the fuel pressure regulator is leaking fuel, go to step  25 . If fuel pressure regulator is not leaking fuel, go to next step.
  4. Command the fuel pump relay OFF with a scan tool. Turn ignition off. Turn OFF all accessories. Install the Gauge Bar Set with the Fuel Pressure Adapter and the Drain Hose. Turn ignition on, with engine off. DO NOT start the engine. Command the fuel pump relay ON with a scan tool. Observe the fuel pressure gauge with the fuel pump commanded ON. Is the fuel pressure 39-49 psi (269-338 kPa)? If yes, go to next step. If fuel pressure is not 39-49 psi (269-338 kPa), go to step  9 .
    5. NOTE: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.
  5. Monitor the fuel pressure gauge for 5 minutes. Does the fuel pressure decrease by more than 8 psi (55 kPa)? If yes, go to step  7 . If fuel pressure remains constant, go to next step.
  6. Operate the vehicle within the conditions to reproduce the original symptoms. Monitor the O2 and the Fuel Trim parameters with a scan tool. If scan tool parameters indicate a lean condition, go to step  13 . If scan tool parameters do not indicate a lean condition, see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 3.0L SATURN "L" SERIES article.
  7. Perform the following:
    1. Turn ignition off.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  .
    3. Remove Fuel Pressure Gauge from the fuel pressure test connection.
    4. Disconnect the chassis fuel hoses from the engine compartment fuel pipes.
    5. Connect the fuel feed hose to the inlet side of the Fuel Pressure/flow Adapter using the 3/8" male Fuel Pressure Adapter Line.
    6. Connect the fuel return hose to the outlet side of the Fuel Pressure/flow Adapter using the 5/16" male Fuel Pressure Adapter Line.
    7. Close the valve on the Fuel Pressure/flow Adapter.
    8. Turn ignition on, with engine off.
    9. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
    10. Record the fuel pressure.
    11. Command the fuel pump relay OFF.
    12. Monitor the fuel pressure gauge for 5 minutes.

    If the fuel pressure decrease by more than 8 psi (55 kPa, go to step  27 . If fuel pressure remains constant, go to next step.

  8. Perform the following:
    1. Turn ignition off.
    2. Open the valve on the Fuel Pressure/Flow Adapter.
    3. Disconnect the fuel feed hose from the inlet side of the Fuel Pressure/Flow Adapter.
    4. Connect the fuel feed hose to the engine compartment fuel pipe.
    5. Connect the fuel rail side of the engine compartment fuel return pipe to the inlet side of the Fuel Pressure/Flow Adapter using the 5/16" female Fuel Pressure Adapter Line.
    6. Close the valve on the Fuel Pressure/Flow Adapter.
    7. Turn ignition on, with engine off.
    8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
    9. Record the fuel pressure.
    10. Command the fuel pump relay OFF.
    11. Monitor the fuel pressure gauge for 5 minutes.

    If the fuel pressure decrease by more than 8 psi (55 kPa), go to step  20 . If fuel pressure remains constant, go to step  25 .

  9. If the fuel pressure more than 60 psi (414 kPa), go to next step. If fuel pressure is less than 60 psi (414 kPa), go to step  13 .
  10. Perform the following:
    1. Turn ignition off.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  .
    3. Disconnect the fuel return hose from the engine compartment fuel return pipe.
    4. Connect the fuel rail side of the engine compartment fuel return pipe to the inlet side of the Fuel Pressure/Flow Adapter using the 5/16" female Fuel Pressure Adapter Line.
    5. Connect the return hose from the Fuel Pressure/Flow Adapter to the outlet side of the Fuel Pressure/Flow Adapter.
    6. Place the other end of the return hose into the fuel filler pipe.
    7. Cap the pressure test port on the Fuel Pressure/Flow Adapter with the Fuel Pressure Adapter Cap.
    8. Open the valve on the Fuel Pressure/Flow Adapter.
    9. Turn ignition on, with engine off.
    10. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
    11. Monitor the fuel pressure gauge while the fuel pump is operating.

    If the fuel pressure is less than 75 psi (517 kPa), go to next step. If fuel pressure is more than 75 psi (517 kPa), go to step  17 .

  11. Perform the following:
    1. Turn ignition off.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  .
    3. Remove the Fuel Pressure/Flow Adapter.
    4. Connect the fuel return hose to the engine compartment fuel return pipe.
    5. Raise the vehicle.
    6. Disconnect the chassis fuel return pipe at the passenger side front wheel well area.
    7. Connect the engine side of the fuel return pipe to the inlet side of Fuel Pressure/Flow Adapter using the Fuel Pressure Adapter Lines 5/16" Female Fuel Pressure Adapter Line.
    8. Connect the return hose from the Fuel Pressure/Flow Adapter to the outlet side of Fuel Pressure/Flow Adapter.
    9. Place the other end of the return hose into the fuel filler pipe.
    10. Cap the pressure test port on the Fuel Pressure/Flow Adapter with the Fuel Pressure Adapter Cap.
    11. Open the valve on the Fuel Pressure/Flow Adapter.
    12. Turn ignition on, with engine off.
    13. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
    14. Monitor the fuel pressure gauge while the fuel pump is operating.

    If the fuel pressure is less than 75 psi (517 kPa), go to next step. If fuel pressure is more than 75 psi (517 kPa), go to step  22 .

  12. Perform the following:
    1. Turn ignition off.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  .
    3. Remove the Fuel Pressure/Flow Adapter.
    4. Connect the chassis fuel return pipe at the passenger side front wheelwell area.
    5. Remove the fuel pipe shield.
    6. Disconnect the fuel return pipe at the front of the fuel tank.
    7. Connect the engine side of the fuel return pipe to the inlet side of Fuel Pressure/Flow Adapter using the 5/16" female Fuel Pressure Adapter Line.
    8. Connect the return hose from the Fuel Pressure/Flow Adapter to the outlet side of Fuel Pressure/Flow Adapter.
    9. Place the other end of the return hose into the fuel filler pipe.
    10. Cap the pressure test port on the Fuel Pressure/Flow Adapter with the Fuel Pressure Adapter Cap.
    11. Open the valve on the Fuel Pressure/Flow Adapter.
    12. Turn ignition on, with engine off.
    13. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.
    14. Monitor the fuel pressure gauge while the fuel pump is operating.

    If the fuel pressure is less than 75 psi (517 kPa), go to step  19 . If fuel pressure is more than 75 psi (517 kPa), go to step  24 .

  13. Perform the following:
    1. Turn ignition off.
    2. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  .
    3. Remove the Fuel Pressure Gauge from the fuel pressure test connection.
    4. Disconnect the chassis fuel hoses from the engine compartment fuel pipes.
    5. Connect the fuel feed hose to the inlet side of the Fuel Pressure/Flow Adapter using the 3/8" male Fuel Pressure Adapter Line.
    6. Connect the fuel return hose to the outlet side of the Fuel Pressure/Flow Adapter using the 5/16" male Fuel Pressure Adapter Line.
    7. Connect the Fuel Pressure Gauge to the Fuel Pressure/Flow Adapter.
    8. Open the valve on the Fuel Pressure/Flow Adapter.
    9. Turn ignition on, with engine off.
    10. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

    If the fuel pressure is more than 55 psi (379 kPa), go to step  25 . If fuel pressure is less than 55 psi (379kPa), go to next step.

  14. Perform the following:
    1. Turn ignition off.
    2. Remove the Fuel Pressure/Flow Adapter.
    3. Connect the chassis fuel hoses to the engine compartment fuel pipes.
    4. Raise the vehicle.
    5. Disconnect the fuel feed pipe at the fuel filter inlet.
    6. Connect the fuel feed pipe to the inlet side of the Fuel Pressure/Flow Adapter using the 3/8" male Fuel Pressure Adapter Line.
    7. Connect the return hose from the Fuel Pressure/Flow Adapter to the outlet side of Fuel Pressure/Flow Adapter.
    8. Place the other end of the return hose into the fuel filler pipe.
    9. Open the valve on the Fuel Pressure/Flow Adapter.
    10. Turn ignition on, with engine off.
    11. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

    If the fuel pressure is more than 55 psi (379 kPa), go to next step. If fuel pressure is less than 55 psi (379kPa), go to step  18 .

  15. Perform the following:
    1. Turn ignition off.
    2. Remove the Fuel Pressure/Flow Adapter from the fuel filter inlet.
    3. Connect the fuel feed pipe to the fuel filter inlet.
    4. Disconnect the fuel feed pipe at the fuel filter outlet.
    5. Connect the inlet side of Fuel Pressure/Flow Adapter to the fuel filter outlet using the 3/8" female Fuel Pressure Adapter Line.
    6. Open the valve on the Fuel Pressure/Flow Adapter.
    7. Turn ignition on, with engine off.
    8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

    If the fuel pressure is more than 55 psi (379 kPa), go to next step. If fuel pressure is less than 55 psi (379kPa), go to step  26 .

  16. Perform the following:
    1. Turn ignition off.
    2. Remove the Fuel Pressure/Flow Adapter from the fuel filter outlet.
    3. Connect the fuel feed pipe to the fuel filter outlet.
    4. Disconnect the chassis fuel feed pipe at the passenger side front wheel well area.
    5. Connect the fuel tank side of the fuel feed pipe to the inlet side of the Fuel Pressure/Flow Adapter using the 3/8" male Fuel Pressure Adapter Line.
    6. Open the valve on the Fuel Pressure/Flow Adapter.
    7. Turn ignition on, with engine off.
    8. Command the fuel pump relay ON for a minimum of 10 seconds with a scan tool.

    If the fuel pressure is more than 55 psi (379 kPa), go to step  21 . If fuel pressure is less than 55 psi (379kPa), go to step  23 .

  17. Inspect the fuel rail return pipe and the fuel rail outlet passage for a restriction. Did you find and correct a restriction? If yes, go to step  28 . If no, go to step  25 .
  18. Inspect the rear fuel feed pipe on the fuel tank for damage and for a restriction. Did you find and correct a restriction? If yes, go to step  28 . If no, go to step  27 .
  19. Inspect the rear fuel return pipe on the fuel tank for a restriction. Did you find and correct a restriction? If yes, go to step  28 . If no, go to step  27 .
  20. Perform the following:
    1. Turn ignition off.
    2. Open the valve on the Fuel Pressure/Flow Adapter.
    3. Remove the Fuel Pressure/Flow Adapter from the fuel return pipe.
    4. Connect the fuel return hose to the engine compartment fuel pipe.
    5. Raise the fuel rail, with the fuel lines connected. See FUEL RAIL & INJECTORS under FUEL SYSTEMS in REMOVAL & INSTALLATION - SATURN "L" SERIES article.
    6. Turn ignition on, with engine off.
    7. Command the fuel pump relay ON with a scan tool.
    8. Locate and replace the leaking fuel injector. See FUEL RAIL & INJECTORS under FUEL SYSTEMS in REMOVAL & INSTALLATION - SATURN "L" SERIES article.

    Did you complete the replacement? If yes, go to step  28 .

  21. Replace the engine compartment fuel feed pipe. After replacement is complete, go to step  28 .
  22. Replace the engine compartment fuel return pipe. After replacement is complete, go to step  28 .
  23. Replace the chassis fuel feed pipe. After replacement is complete, go to step  28 .
  24. Replace the chassis fuel return pipe. After replacement is complete, go to step  28 .
  25. Inspect for a missing or damaged fuel pressure regulator "O" ring seal before replacing the fuel pressure regulator. If fuel pressure "O" ring seal is okay, replace the fuel pressure regulator. See FUEL PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. After replacement is complete, go to step  28 .
  26. Replace the fuel filter. See FUEL FILTER under FUEL SYSTEMS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. After replacement is complete, go to step  28 .
  27. Replace the fuel pump module. See FUEL PUMP MODULE under FUEL SYSTEMS in REMOVAL & INSTALLATION - SATURN "L" SERIES article. After replacement is complete, go to step  28 .
  28. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step  4 .
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