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Home >> GMC >> 2003 >> Jimmy 2D Utility, Part Time, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures - 4.3L >> Fuel Systems >> Fuel System Pressure Test >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. After performing diagnostic system check, go to next step.
    2. NOTE: Inspect fuel system for damage or external leaks before proceeding with this test.
  2. Turn ignition on, with engine off. Command fuel pump relay on with a scan tool. Does fuel pump operate? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  3. Verify that adequate fuel is in fuel tank before proceeding with this diagnostic. Turn ignition off. Turn off all accessories. Install fuel pressure gauge. Turn ignition on, with engine off. Fuel pump relay may need to be commanded on a few times in order to obtain highest possible fuel pressure. Do not start engine. Command fuel pump relay on with a scan tool. Observe fuel pressure gauge with fuel pump commanded on. Is fuel pressure within 55-62 psi (379-427 kPa)? If yes, go to next step. If no, go to step  10.
    4. NOTE: The fuel pressure may vary slightly when fuel pump stops operating. After fuel pump stops operating, fuel pressure should stabilize and remain constant.
  4. Monitor fuel pressure gauge for one minute. Does fuel pressure decrease by more than 5 psi (34 kPa)? If yes, go to step  8. If no, go to next step.
  5. Release fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. Does fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step  22. If no, go to next step.
  6. Turn ignition on, with engine off. Monitor fuel pressure gauge. Start engine. Does fuel pressure decrease by 3-10 psi (21-69 kPa) when engine is started? If yes, go to next step. If no, go to step  21.
  7. Operate vehicle within conditions to reproduce original symptoms. Monitor O2 and fuel trim parameters with a scan tool. Do any of scan tool parameters indicate a lean condition? If yes, go to step  15. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article.
  8. Turn ignition off. Release fuel pressure. Raise and support vehicle. Disconnect fuel feed pipe from fuel filter outlet. Disconnect rear fuel return pipe from chassis fuel pipe. Drain any remaining fuel into an approved gasoline container. Install Fuel Line Shut-Off Adapters (J-37287) between rear fuel pipes and chassis fuel pipes. Open valves on fuel pipe shut-off adapters. Turn ignition on, with engine off. Command fuel pump relay ON with a scan tool. Bleed air from fuel pressure gauge. Command fuel pump relay ON and OFF with a scan tool. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step  17. If no, go to next step.
  9. Turn ignition off. Open fuel feed pipe shut-off valve. Turn ignition on, with engine off. Command fuel pump relay on and off with a scan tool. Close fuel return pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step  21. If no, go to step  18.
  10. Is fuel pressure more than 62 psi (427 kPa)? If yes, go to step  12. If no, go to next step.
  11. Is fuel pressure more than zero psi? If yes, go to step  14. If no, go to step  15.
  12. Turn ignition off. Release fuel pressure. Disconnect fuel return hose from fuel rail return pipe. Attach a length of flexible hose to fuel rail return pipe. Place open end of flexible fuel hose into an approved gasoline container. Turn ignition on, with engine off. Monitor fuel pressure gauge while fuel pump is operating. Is fuel pressure within 55-62 psi (379-427 kPa)? If yes, go to step  20. If no, go to next step.
  13. Inspect fuel rail outlet passage and fuel rail return pipe for a restriction. Did you find and correct condition? If yes, go to step  23. If no, go to step  21.
  14. Turn ignition off. Release fuel pressure. Disconnect fuel return hose from fuel rail return pipe. Install Fuel Line Shut-Off Adapter (J-37287) between fuel return pipe and fuel rail. Open valve in fuel pipe shut-off adapter. Turn ignition on, with engine off. Bleed air from fuel pressure gauge. Monitor fuel pressure gauge. DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage fuel system. Command fuel pump relay on with a scan tool. Slowly close valve in fuel return pipe shut-off adapter, while fuel pump is operating. Does fuel pressure increase to more than 62 psi (427 kPa)? If yes, go to step  21. If no, go to next step.
  15. Inspect for restricted fuel filter or fuel feed pipe. Did you find and correct condition? If yes, go to step  23. If no, go to next step.
  16. Inspect harness connectors and ground circuits of fuel pump for poor connections. Did you find and correct condition? If yes, go to step  23. If no, go to next step.
  17. Remove fuel sender assembly. Inspect fuel pump flex hose for damage, in-tank fuel pump harness connectors for poor connections, fuel strainer for a restriction and fuel tank for contaminants. Did you find and correct condition? If yes, go to step  23. If no, go to step  22.
  18. Open fuel return pipe shut-off valve. Remove upper intake manifold. Install engine compartment fuel feed and fuel return pipes to fuel meter body. Turn ignition on, with engine off. Inspect for a fuel leak from fuel pressure regulator. Is fuel pressure regulator leaking fuel? If yes, go to step  21. If no, go to next step.
  19. Remove fuel injectors from intake manifold in order to isolate leaking fuel injector. After replacing injector(s), go to step  23.
  20. Repair restricted fuel return pipe. After repairs, go to step  23.
  21. Replace fuel pressure regulator. After replacing fuel pressure regulator, go to step  23.
  22. Replace fuel sender. After replacing fuel sender, go to next step.
  23. Operate system in order to verify repair. Did you correct condition? If yes, system is okay. If no, go to step  3.
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