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Home >> Pontiac >> 2001 >> Aztek Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Fuel System (Gasoline) >> Fuel System Diagnosis >> Diagnostic Procedure
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Diagnostic Procedure

  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to step  2. If no, Go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK .
    2. IMPORTANT: Inspect the fuel system for damage or external leaks before proceeding with this diagnostic.
    1. Turn ON the ignition, with the engine OFF.
    2. Command the fuel pump ON with a scan tool.
    3. Does the fuel pump operate? If yes, go to step  3. If no, Go to FUEL PUMP ELECTRICAL CIRCUIT .
    3. IMPORTANT: Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic.
    1. Turn OFF the ignition.
    2. Turn OFF all accessories.
    3. Remove the engine cover. Refer to Engine Cover Replacement in Interior Trim.
      CAUTION: Wrap a shop towel around the fuel pressure connection in order to reduce the risk of fire and personal injury. The towel will absorb any fuel leakage that occurs during the connection of the fuel pressure gauge. Place the towel in an approved container when the connection of the fuel pressure gauge is complete.
    4. Install the fuel pressure gauge.
    5. Place the bleed hose of the fuel pressure gauge into an approved gasoline container.
    6. Turn ON the ignition, with the engine OFF.
    7. Command the fuel pump ON with a scan tool.
    8. Bleed the air out of the fuel pressure gauge.
      IMPORTANT: It may be necessary to command the fuel pump ON a few times in order to obtain the highest possible fuel pressure. Do Not start the engine.
    9. Command the fuel pump ON with a scan tool.
    10. Observe the fuel pressure gauge, with the fuel pump commanded ON.
    11. Is the fuel pressure within 414-455 kPa (60-66psi)? If yes, go to step  4. If no, go to step  10.
    4. IMPORTANT: 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.
  4. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure drop more than 34 kPa (5 psi)? If yes, go to  8. If no, go to  5.
    1. Relieve the fuel pressure to the first specified value.
    2. Monitor the fuel pressure gauge for 5 minutes.
    3. Does the fuel drop more than 14 kPa (2 psi)? If yes, go to  22. If no, go to step  6
    1. Turn ON the ignition, with the engine OFF.
    2. Monitor the fuel pressure gauge.
    3. Start the engine.
    4. Does the fuel pressure drop 21-69 kPa (3-10 psi) when the engine is started? If yes, go to  7. If no, go to  21.
    1. Operate the vehicle within the conditions of the customers concern.
    2. Monitor the fuel related parameters with a scan tool.
    3. Do any of the scan tool parameters indicate a lean condition? If yes, go to  15. If no, Go to SYMPTOMS (GASOLINE) .
    1. Turn OFF the ignition.
    2. Relieve the fuel pressure. Refer to FUEL SYSTEM PRESSURE RELIEF .
    3. Disconnect the fuel filter and the fuel return union fitting. Refer to Fuel Filter Replacement.
    4. Drain any remaining fuel into an approved gasoline container.
    5. Install the J 42873-2 Fuel Pipe Shut- off Adapters and J 42873-1 in place of the fuel filter and the union fitting.
    6. Open the valves on the fuel pipe shut- off adapters.
    7. Turn ON the ignition, with the engine OFF.
    8. Command the fuel pump ON with a scan tool.
    9. Bleed the air from the fuel pressure gauge.
    10. Command the fuel pump ON and then OFF with a scan tool.
    11. Close the fuel feed pipe shut-off valve.
    12. Monitor the fuel pressure gauge for 1 minute.
    13. Does the fuel pressure remain constant? If yes, go to  17. If no, go to  9.
    1. Turn OFF the ignition.
    2. Open the fuel feed pipe shut-off valve.
    3. Turn ON the ignition, with the engine OFF.
    4. Command the fuel pump ON and then OFF with a scan tool.
    5. Close the fuel return pipe shut-off valve.
    6. Monitor the fuel pressure gauge for 1 minute.
    7. Does the fuel pressure remain constant? If yes, go to  21. If no, go to  18.
  10. Is the fuel pressure above 455 kPa (66 psi)? If yes, go to  12. If no, go to  11.
  11. Is the fuel pressure above 0 kPa (0 psi)? If yes, go to  14. if no, go to  15.
    1. Turn OFF the ignition.
    2. Relieve the fuel pressure. Refer to FUEL SYSTEM PRESSURE RELIEF .
    3. Disconnect the rear fuel return pipe union fitting located near the fuel filter.
    4. Attach a length of flexible fuel hose to the fuel chassis pipe.
    5. Place the open end of the flexible fuel hose into an approved gasoline container.
    6. Turn ON the ignition, with the engine OFF.
    7. Monitor the fuel pressure gauge while the fuel pump is operating.
    8. Is the fuel pressure within 414-455 kPa (59-66 psi)? If yes, go to  20. If no, go to  13.
    1. Inspect the fuel rail outlet passage and the fuel return chassis pipe for a restriction.
    2. Did you find and correct the condition? If yes, go to  23. If no, go to  21.
    1. Turn OFF the ignition.
    2. Relieve the fuel pressure. Refer to FUEL SYSTEM PRESSURE RELIEF .
    3. Disconnect the rear fuel return pipe union fitting located near the fuel filter.
    4. Install the J 42873-2 in place of the fuel return pipe union.
    5. Open the valve in the fuel pipe shut-off adapter.
    6. Turn ON the ignition with the engine OFF.
    7. Bleed the air from the fuel system.
    8. Monitor the fuel pressure gauge.
      NOTE: DO NOT allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel system.
    9. Slowly close the valve in the fuel return pipe shut-off adapter.
    10. Command the fuel pump ON with a scan tool.
    11. Does the fuel pressure rise above 455 kPa (66 psi)? If yes, go to  21. If no, go to  15.
    1. Inspect the following for a restriction:
      • Fuel filter
      • Fuel feed pipe
    2. Did you find and correct the condition? If yes, go to  23. If no, go to  16.
    1. Inspect the harness connectors and ground circuits of the fuel pump for poor connections. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
    2. Did you find and correct the condition? If yes, go to  23. If no, go to  17.
    1. Remove the fuel sender assembly. Refer to Fuel Sender Assembly Replacement.
    2. Inspect the following items:
      • The fuel pump flex hose for damage
      • The in tank fuel pump harness connectors for poor connections
      • The fuel strainer for a restriction
      • Contaminates in the fuel tank
    3. Did you find and correct the condition? If yes, go to  23. If no, go to  22.
    1. Open the fuel return shut-off valve.
    2. Remove the fuel meter body. Refer to REMOVAL & INSTALLATION (4.3L, 5.0L & 5.7L) .
    3. Install the engine compartment fuel feed and fuel return pipes to the fuel meter body.
    4. Turn ON the ignition, with the engine OFF.
    5. Inspect for a fuel leak from the fuel pressure regulator.
    6. Is the fuel pressure regulator leaking fuel? If yes, go to  21. If not, go to  19.
    1. Remove the fuel injector poppet nozzles from the intake manifold in order to isolate the leaking fuel injector. Refer to REMOVAL & INSTALLATION (4.3L, 5.0L & 5.7L) .
    2. Did you complete the replacement? If yes, go to  23.
    1. Locate and repair the restricted fuel return line between the chassis fuel pipe and the fuel tank.
    2. Is the repair complete? If yes, go to  23.
    21. IMPORTANT: Inspect for a missing or damaged O-ring seal before replacing the fuel pressure regulator.
    1. Replace the fuel pressure regulator. Refer to Fuel Pressure Regulator Replacement.
    2. Is the replacement complete? If yes, go to  23.
    1. Replace the fuel pump. Refer to Fuel Sender Assembly Replacement.
    2. Is the replacement complete? If yes, go to  23.
    1. Operate the system in order to verify the repair.
    2. Did you correct the condition? If yes, system OK. If no , go to  3.
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