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Home >> Pontiac >> 2002 >> Aztek AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Basic Fuel System Checks (Gasoline) >> Fuel System Pressure Test (4.3L) >> Diagnostic Procedure
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Diagnostic Procedure

  1. Did you perform a Diagnostic System Check-Engine Controls? If yes, go to next step. If no, perform DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP or SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article.
  2. Inspect the fuel system for damage or external leaks before proceeding with this diagnostic. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Does the fuel pump operate? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS (GASOLINE) in SYSTEM & COMPONENT TESTING - TRUCKS article.
  3. Verify there is adequate fuel in the fuel tank before proceeding with this diagnostic. Turn OFF the ignition. Turn OFF all accessories. Install the fuel pressure gauge. Turn ON the ignition, with the engine OFF. 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. Command the fuel pump ON with a scan tool. Observe the fuel pressure gauge, with the fuel pump commanded ON. Is the fuel pressure 60-66 psi (415-455 kPa) for VIN W models or 55-62 psi (379-427 kPa) for VIN X models? If yes, go to next step. If no, go to step  10.
    NOTE: To identify model Vehicle Identification Number (VIN), see GENERAL MOTORS INTRODUCTION - TRUCKS article.
  4. 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. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure decrease by more than 5 psi (34 kPa). If yes, go to step  8. If no, go to next step.
  5. Relieve the fuel pressure to 10 psi (69 kPa). Monitor the fuel pressure gauge for 5 minutes. Does the fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step  22. If no, go to next step.
  6. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gauge. Start the engine. Does the fuel pressure decrease by 3-10 psi (21-69 kPa) when the engine is started? If yes, go to next step. If no, go to step  21.
  7. Operate the vehicle within the conditions of the customer's concern. Monitor the fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? If yes, go to step  15. If no, diagnose by symptom. See SYMPTOMS (GASOLINE) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
  8. Turn OFF the ignition. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel feed pipe and the rear fuel return pipe from the chassis fuel pipes. Drain any remaining fuel into an approved gasoline container. Install the fuel pipe shut-off adapters between the rear fuel pipes and the chassis fuel pipes. Open the valves on the fuel pipe shut-off adapters. Turn ON the ignition, with the engine OFF. Command the fuel pump ON with a scan tool. Bleed the air from the fuel pressure gauge. Command the fuel pump ON and then OFF with a scan tool. Close the fuel feed pipe shut-off valve. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure remain constant at 3-10 psi (21-69 kPa)? If yes, go to step  17. If no, go to next step.
  9. Turn OFF the ignition. Open the fuel feed pipe shut-off valve. Turn ON the ignition, with the engine OFF. Command the fuel pump ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gauge for 1 minute. Does the fuel pressure remain constant? If yes, go to step  21. If no, go to step  18.
  10. Is the fuel pressure more than 66 psi (455 kPa) for VIN W models or 62 psi (427 kPa) for VIN X models? If yes, go to step  12. If no, go to next step.
  11. Is the fuel pressure more than 0 psi (0 kPa)? If yes, go to step  14. If no, go to step  15.
  12. Turn OFF the ignition. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel return pipe from the chassis pipe. Attach a length of flexible hose to the chassis fuel pipe. Place the open end of the flexible fuel hose into an approved gasoline container. Turn ON the ignition, with the engine OFF. Monitor the fuel pressure gauge while the fuel pump is operating. Is the fuel pressure 60-66 psi (415-455 kPa) for VIN W models or 55-62 psi (379-427 kPa) for VIN X models? If yes, go to step  20. If no, go to next step.
  13. Inspect the fuel rail outlet passage and the fuel return chassis pipe for a restriction. Did you find and correct the condition? If yes, go to step  23. If no, go to step  21.
  14. Turn OFF the ignition. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  under BASIC FUEL SYSTEM CHECKS (GASOLINE). Remove the EVAP canister. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Disconnect the rear fuel return pipe from the chassis pipe. Install the fuel pipe shut-off adapter between the rear fuel return pipe and the chassis fuel pipe. Open the valve in the fuel pipe shut-off adapter. Turn ON the ignition, with the engine OFF. Bleed the air from the fuel system. Monitor the fuel pressure gauge. DO NOT allow the fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage the fuel system. Slowly close the valve in the fuel return pipe shut-off adapter. Command the fuel pump ON with a scan tool. Does the fuel pressure increase to more than 66 psi (455 kPa) for VIN W models or 62 psi (427 kPa) for VIN X models? If yes, go to step  21. If no, go to next step.
  15. Inspect the fuel filter and fuel feed pipe for restrictions. Did you find and correct the condition? If yes, go to step  23. If no, go to next step.
  16. Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step  23. If no, go to next step.
  17. Remove the fuel sender assembly. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. 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. Contaminants in the fuel tank. Did you find and correct the condition? If yes, go to step  23. If no, go to step  22.
  18. Open the fuel return pipe shut-off valve. Remove the fuel meter body. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Install the engine compartment fuel feed and fuel return pipes to the fuel meter body. Turn ON the ignition, with the engine OFF. Inspect for a fuel leak from the fuel pressure regulator. Is the fuel pressure regulator leaking fuel? If yes, go to step  21. If no, go to next step.
  19. Remove the fuel injector poppet nozzles from the intake manifold in order to isolate the leaking fuel injector. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.
  20. Locate and repair the restricted fuel return pipe between the chassis fuel pipe and the fuel tank. Did you complete the repair? After repair is complete, go to  23.
  21. Inspect for a missing or damaged "O" ring seal before replacing the fuel pressure regulator. Replace the fuel pressure regulator. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, go to  23.
  22. Replace the fuel pump. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, go to next step.
  23. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step  3.
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