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Home >> Pontiac >> 2003 >> Aztek FWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> 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 - 3.4L AZTEK & RENDEZVOUS article. After performing diagnostic system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Does the fuel pump operate? If yes, go to next step. If no, diagnose fuel pump electrical circuit. See FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 3.4L AZTEK & RENDEZVOUS article.
  3. Turn ignition off. Turn off all accessories. Install Fuel Pressure Gauge (J-34730-1A) and Fuel Pressure Gauge Fitting Adapter (J-34730-262). Turn ignition on, with engine off. Using scan tool, command fuel pump (fuel pump runs for about 2 seconds) in order to obtain the highest possible fuel pressure. DO NOT start engine. Observe fuel pressure gauge with fuel pump commanded on. Is fuel pressure within 52-59 psi (358-405 kPa)? If yes, go to next step. If no, go to step  12 .
  4. Monitor fuel pressure gauge for one minute. Does the fuel pressure drop more than 5 psi (34 kPa)? If yes, go to step  9 . If no, go to next step.
  5. Relieve fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. Does fuel pressure drop more than 2 psi (14 kPa)? If yes, go to step  24 . If no, go to next step.
  6. Turn ignition off for 15 seconds. Turn ignition on, with engine off. Monitor fuel pressure gauge. Start engine. Does fuel pressure drop by 3-10 psi (21-69 kPa) when engine is started? If yes, go to next step. If no, go to step  8 .
  7. Operate the vehicle within the conditions of the customers concern. Monitor fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? If yes, go to step  17 . If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTICS - 3.4L AZTEK & RENDEZVOUS article.
  8. Disconnect vacuum hose from fuel pressure regulator. Monitor fuel pressure gauge. Operate engine at idle. Using a hand-held vacuum pump, apply 12-14 in. Hg (34-47 kPa) to fuel pressure regulator. Does fuel pressure drop to 3-10 psi (21-69 kPa) when vacuum is applied? If yes, go to step  21 . If no, go to step  23 .
  9. Turn ignition off. Remove vacuum hose from fuel pressure regulator. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Inspect for fuel leak from fuel pressure regulator vacuum port. Is fuel pressure regulator leaking fuel? If yes, go to step  23 . If no, go to next step.
  10. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Disconnect fuel feed hose and fuel return hose from fuel rail pipes. Install a Fuel Line Shut-Off Adapters (J-37287) between fuel hoses and the fuel rail pipes. Open valves on fuel pipe shut-off adapters. Turn ignition on, with engine off. Command fuel pump on using scan tool. Obtain highest possible fuel pressure. Bleed air from fuel pressure gauge. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step  19 . If no, go to next step.
  11. Turn ignition off. Open fuel feed pipe shut-off valve. Turn ignition on, with engine off. Command fuel pump ON and then OFF with scan tool. Close fuel return pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does the fuel pressure remain constant? If yes, go to step  23 . If no, go to step  20 .
  12. Is fuel pressure greater than 59 psi (427 kPa)? If yes, go to step  14 . If no, go to next step.
  13. Is fuel pressure greater than zero psi? If yes, go to step  16 . If no, go to step  17 .
  14. Turn ignition off. Relieve fuel pressure. Disconnect fuel return hose from fuel rail return pipe. Attach a length of flexible fuel hose to fuel rail outlet passage. Place open end of the flexible fuel hose into an approved gasoline container. Turn ignition on, with engine off. Using scan tool, monitor fuel pressure gauge while fuel pump is operating. Is fuel pressure within 52-59 psi (358-405 kPa)? If yes, go to step  22 . If no, go to next step.
  15. Inspect the fuel rail return pipe and fuel rail outlet passage for a restriction. Did you find and correct the condition? If yes, go to step  25 . If no, go to step  23 .
  16. Turn ignition off. Relieve fuel pressure. Disconnect fuel return hose from fuel rail return pipe. Install a Fuel Line Shut-Off Adapters (J-37287) between fuel return pipe and fuel rail. Open valve in the fuel pipe shut-off adapter. Turn ignition on, with engine off. Bleed air from fuel system. Monitor fuel pressure gauge. DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage fuel system. Slowly close valve in fuel return pipe shut-off adapter. Command fuel pump on with scan tool. Does the fuel pressure rise to greater than 52 psi (358 kPa)? If yes, go to step  23 . If no, go to next step.
  17. Inspect fuel filter and fuel feed pipe for restriction. Did you find and correct the condition? If yes, go to step  25 . If no, go to next step.
  18. Inspect the harness connectors and ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step  25 . If no, go to next step.
  19. Remove the fuel sender assembly. Inspect fuel pump flex hose for damage, fuel pump harness connectors for poor connections, fuel strainer for a restriction or contaminates in fuel tank Did you find and correct the condition? If yes, go to step  25 . If no, go to step  24 .
  20. Turn ignition off. Raise fuel rail with fuel lines connected. Turn ignition on, with engine off. Command fuel pump on with scan tool. Locate and replace the leaking fuel injector. After repairs, go to step  25 .
  21. Repair vacuum source to fuel pressure regulator. After repairs, go to step  25 .
  22. Locate and repair restricted fuel return line. After repairs, go to step  25 .
  23. Replace fuel pressure regulator. After replacing fuel pressure regulator, go to step  25 .
  24. Replace fuel pump. After replacing fuel pump, go to next step.
  25. 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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