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Fuel System Pressure Test (Aurora)

CAUTION: Begin fuel system trouble shooting and diagnosis with checking fuel injection system pressure. High fuel pressure may be present in fuel lines and component parts. Relieve fuel pressure before disconnecting any fuel system components.
  1. If powertrain diagnostic system check has already been performed, go to next step. If powertrain diagnostic system check has not been performed, go to POWERTRAIN DIAGNOSTIC SYSTEM CHECK under DIAGNOSTIC SYSTEM CHECKS in appropriate SELF-DIAGNOSTICS article.
  2. Ensure ignition is on. Using scan tool, command fuel pump on. If fuel pump operates, go to next step. If fuel pump does not operate, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS  under NO-START - ENGINE CRANKS OKAY (3.5L & 4.0L AURORA)
  3. Turn ignition off. Ensure fuel tank has adequate fuel. Turn A/C system off. Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. Pace fuel pressure gauge bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition several times to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be within specification. See FUEL PRESSURE SPECIFICATIONS (AURORA)  table. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step  12.
    FUEL PRESSURE SPECIFICATIONS (AURORA)

    Application (1) psi (kg/cm2 )
    3.5L & 4.0L 41-47 (2.9-3.3)
    (1) Specification listed is with ignition on and engine off.
  4. Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant. Note fuel pressure when fuel pump stops running. If fuel pressure decreases more than 5 psi in one minute, go to step  9. If fuel pressure does not decrease more than 5 psi in one minute, go to next step.
  5. Relieve fuel pressure until pressure is 10 psi. Monitor fuel pressure gauge for 5 minutes. If fuel pressure decreases more than 2 psi in 5 minutes, go to step  24. If fuel pressure does not decrease more than 2 psi in 5 minutes, go to next step.
  6. Turn ignition off for 15 seconds. Turn ignition on. Observe fuel pressure gauge. Start engine. If fuel pressure decreases 3-10 psi, go to next step. If fuel pressure does not decrease 3-10 psi, go to step  8.
  7. Operate vehicle within conditions of customers concern. If any scan tool parameters indicate a lean condition, go to step  17. If no scan tool parameters indicate a lean condition, diagnose by symptom. See appropriate TROUBLE SHOOTING - NO CODES article.
  8. Disconnect vacuum hose from fuel pressure regulator. With engine idling, apply 12-14 in. Hg of vacuum to fuel pressure regulator. If fuel pressure decreases by 3-10 psi, go to step  21. If fuel pressure does not decrease 3-10 psi, go to step  23.
  9. Turn ignition off. Disconnect vacuum hose from fuel pressure regulator. Turn ignition on. Using scan tool, command fuel pump on. Check for fuel leak at pressure regulator vacuum port. If pressure regulator is leaking fuel, go to step  23. If pressure regulator is not leaking fuel, go to next step.
  10. Turn ignition off. Relieve fuel pressure. See FUEL PRESSURE SPECIFICATIONS (AURORA) . Disconnect fuel supply and return hoses at fuel rail. Install Fuel Pipe Shutoff Adapters (J 37287) between fuel hoses and fuel rail pipes. Open valve on fuel pipe shutoff adapters. Place bleed hose into container. Turn ignition on. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge. Using scan tool, command fuel pump on and off. Close valve on fuel supply pipe shutoff adapter. Monitor fuel pressure for one minute. If fuel pressure remains constant, go to step  19. If fuel pressure does not remain constant, go to next step.
  11. Turn ignition off. Open valve on fuel supply pipe shutoff adapter. Turn ignition on. Using scan tool, command fuel pump on and off. Close valve on return pipe shutoff adapter. Monitor fuel pressure for one minute. If fuel pressure remains constant, go to step  23. If fuel pressure does not remain constant, go to step  20.
  12. If fuel pressure is more than 62 psi, go to step  14. If fuel pressure is not more than 62 psi, go to next step.
  13. If fuel pressure is more than zero psi, go to step  16. If fuel pressure is zero psi, go to step  17.
  14. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF (EXCEPT SATURN) . Disconnect fuel return pipe from fuel rail. Attach a flexible fuel hose to fuel rail return outlet passage. Place other end of flexible hose into container. Turn ignition on. Observe fuel pressure gauge with fuel pump running. Fuel pressure should be within specification. See FUEL PRESSURE SPECIFICATIONS (AURORA)  table. If fuel pressure is as specified, go to step  22. If fuel pressure is not as specified, go to next step.
  15. Inspect fuel rail outlet passage for restriction. Repair as necessary. After repairs, go to step  25. If no restriction is found, go to step  23.
  16. Turn ignition off. Relieve fuel pressure. See FUEL PRESSURE SPECIFICATIONS (AURORA) . Disconnect fuel supply and return hoses at fuel rail. Install Fuel Pipe Shutoff Adapters (J 37287) between fuel hoses and fuel rail pipes. Open valve on fuel pipe shutoff adapters. Place bleed hose into container. Turn ignition on. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge. DO NOT allow fuel pressure to exceed 75 psi. Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Slowly close valve on return pipe shutoff adapter. Using scan tool, command fuel pump on. If fuel pressure increases to more than 47 psi, go to step  23. If fuel pressure does not increase to more than 47 psi, go to next step.
  17. Inspect fuel filter and fuel supply pipe for restrictions. Repair as necessary. After repairs, go to step  25. If no problems are found, go to next step.
  18. Inspect fuel pump connectors and ground circuit for poor connections. Repair as necessary. After repairs, go to step  25. If no problems are found, go to next step
  19. Remove fuel pump assembly. Fuel pump can be accessed through an inspection panel in trunk. Inspect fuel pump strainer for restrictions. Check fuel pump flex pipe for leaks. Check for contaminates in fuel tank. Repair as necessary. After repairs, go to step  25. If no problems are found, go to step  24.
  20. Locate and replace leaking fuel injector(s). After repairs, go to step  25.
  21. Locate and repair loss of vacuum to fuel pressure regulator. After repairs, go to step  25.
  22. Locate and repair restriction in fuel return pipe. After repairs, go to step  25.
  23. Replace fuel pressure regulator. After repairs, go to step  25.
  24. Replace fuel pump. After repairs, go to next step.
  25. Turn ignition off. Reconnect all disconnected connectors. Turn ignition on. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. If engine starts and continues to idle, system is okay. If engine does not start or continue to idle, go to step  3.
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