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Fuel System Pressure Test: 3.4L

  1. Perform OBD system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Turn ignition off. Turn A/C system off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. Place fuel pressure gauge bleed hose into container. Connect negative battery cable. Turn ignition on. Bleed air from fuel pressure gauge. Using scan tool, command fuel pump on. Observe fuel pressure with fuel pump running. Fuel pressure should be 52-59 psi (3.7-4.1 kg/cm2 ). If fuel pressure is within specification, go to step  6. If fuel pressure is not within specification, go to next step.
  3. If indicated fuel pressure is greater than 59 psi (4.1 kg/cm2 ), go to step  14. If indicated fuel pressure is not greater than 59 psi (4.1 kg/cm2 ), go to next step.
  4. Check fuel system for leaks. Repair as necessary. After repairs, go to step  21. If no leaks are present, go to next step.
  5. If indicated fuel pressure is greater than zero psi, go to step  7. If indicated fuel pressure is not greater than zero psi, go to step  16.
  6. Monitor fuel pressure. If fuel pressure decreases more than 5 psi (.4 kg/cm2 ) in 10 minutes, go to next step. If pressure does not decrease more than 5 psi (.4 kg/cm2 ) in 10 minutes, go to step  9.
  7. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Connect Fuel Pipe Shutoff Adapters (J-37287) between fuel feed pipe and fuel return pipe at fuel rail. Open fuel feed and close fuel return valves. Turn ignition on. Bleed air from fuel system. Using scan tool, command fuel pump on and wait for pressure to build. If fuel pressure is constant at 52-59 psi (3.7-4.1 kg/cm2 ), go to step  19. If fuel pressure is not as specified, go to next step.
  8. Using scan tool, command fuel pump on. With fuel pump running, close fuel feed valve. If fuel pressure is constant, go to step  17. If fuel pressure is not constant, diagnose fuel injectors. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in appropriate SYSTEM & COMPONENT TESTING article.
  9. If fuel pressure is suspected of dropping off during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of dropping off during acceleration, cruise or hard cornering, go to step  12.
  10. Check in-line fuel filter and fuel feed pipe for restriction. Repair as necessary. After repairs, go to step  21. If no problem is found, go to next step.
  11. Remove fuel sending unit assembly. Check pump strainer for restriction or incorrect installation. Check for leaking fuel pump flex pipe. Ensure fuel pump is correct for vehicle application. Repair as necessary. After repairs, go to step  21. If no problem is found, go to step  17.
  12. Start engine and allow it to reach normal operating temperature. Observe fuel pressure gauge. If fuel pressure decreases 3-10 psi (.2-.7 kg/cm2 ), check for intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure does not decrease 3-10 psi (.2-.7 kg/cm2 ), go to next step.
  13. With engine idling, disconnect vacuum hose from fuel pressure regulator. Apply vacuum (12 in. Hg) to fuel pressure regulator. If fuel pressure decreases 3-10 psi (.2-.7 kg/cm2 ), go to step  18. If fuel pressure does not decrease 3-10 psi (.2-.7 kg/cm2 ), go to step  19.
  14. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Disconnect fuel return pipe. Connect flexible fuel hose to fuel rail return outlet. Place open end of hose into container. Using scan tool, command fuel pump on. Observe fuel pressure gauge. If fuel pressure is 52-59 psi (3.7-4.1 kg/cm2 ), go to step  20. If fuel pressure is not as specified, go to next step.
  15. Check fuel rail outlet for restriction. Repair as necessary. After repairs, go to step  21. If no restriction is found, go to step  19.
  16. Check for clogged in-line fuel filter or fuel pump strainer, restricted fuel feed pipe or leaks in fuel pump flex pipe. Repair as necessary. After repairs, go to step  21. If no problem is found, diagnose fuel pump electrical circuit. See appropriate diagnostic procedure under NO-START DIAGNOSIS .
  17. Replace fuel sending unit assembly. After repairs, go to step  21.
  18. Locate and repair loss of vacuum to fuel pressure regulator. After repairs, go to step  21.
  19. Replace fuel pressure regulator. After repairs, go to step  21.
  20. Repair restriction in fuel return pipe. After repairs, go to next step.
  21. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Reconnect all fuel system components, leaving fuel pressure gauge installed. Turn ignition on. Using scan tool, command fuel pump on. Monitor fuel pressure with fuel pump running. If fuel pressure is constant at 52-59 psi (3.7-4.1 kg/cm2 ), system is okay. If fuel pressure is not as specified, go to step  2.
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