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Fuel System Pressure Test: 4.3L

  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 test port. Using scan tool, command fuel pump on. Bleed air from fuel pressure gauge into container. Using scan tool, command fuel pump on. Monitor fuel pressure with fuel pump running. Fuel pressure should be 60-66 psi (4.2-4.6 kg/cm2 ). If fuel pressure is as specified, go to next step. If fuel pressure is not as specified, go to step  11.
  3. If fuel pressure decreases more than 5 psi (.4 kg/cm2 ) within 10 minutes after fuel pump turns off, go to step  8. If fuel pressure does not decrease more than 5 psi (.4 kg/cm2 ) within 10 minutes after fuel pump turns off, go to next step.
  4. Relieve fuel pressure until gauge reads 10 psi (.7 kg/cm2 ). Monitor fuel pressure. If fuel pressure decreases more than 2 psi (.1 kg/cm2 ) within 10 minutes, go to step  20. If fuel pressure does not decrease more than 2 psi (.1 kg/cm2 ) within 10 minutes, go to next step.
  5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to step  7. If fuel pressure is not suspected of decreasing during acceleration, cruise or hard corning, go to next step.
  6. Start engine and allow it to reach normal operating temperature. Open throttle quickly. Observe fuel pressure. Fuel pressure should increase to about 66 psi (4.6 kg/cm2 ). If fuel pressure increases quickly, check for intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure does not increase quickly, go to next step.
  7. Check for restriction in fuel filter or fuel feed pipe. Check fuel pump electrical circuit for high resistance. If problem is found, go to step  24. If no problem is found, go to step  16.
  8. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Remove EVAP canister. Disconnect fuel feed pipe from either side of fuel filter. Drain remaining fuel from fuel pipe into container. Connect Fuel Pipe Shutoff Adapter (J-42964-1) onto fuel feed pipe. Open valve on shutoff adapter. Install fuel pressure gauge onto shutoff adapter pressure test connection farthest from fuel tank. Reconnect negative battery cable. Turn ignition on. Using scan tool, command fuel pump on. Check for leaks at fittings. Place bleed hose of fuel pressure gauge into container. Bleed air from fuel pressure gauge. Using scan tool, command fuel pump on and wait for pressure to build. Close valve on shutoff adapter connected to fuel feed pipe. Monitor fuel pressure. If fuel pressure remains constant, go to step  20. If fuel pressure does not remain constant, go to next step.
  9. Check fuel feed pipe for leak between shutoff adapter and engine fuel pipe. If a leak is found, go to step  24. If no leaks are found, go to next step.
  10. Open valve in shutoff adapter connected to fuel feed pipe. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Disconnect fuel return pipe located near EVAP canister. Drain remaining fuel from fuel pipe into container. Connect Fuel Pipe Shutoff Adapter (J-42964-2) onto fuel return pipe. Open valve in shutoff adapter connected to fuel return pipe. Reconnect negative battery cable. Turn ignition on. Using scan tool, command fuel pump on and wait for pressure to build. Close valve in shutoff adapter connected to fuel return pipe. Monitor fuel pressure. If fuel pressure remains constant, go to step  21. If fuel pressure does not remain constant, go to step  22.
  11. If fuel pressure is greater than 66 psi (4.6 kg/cm2 ), go to next step. If fuel pressure is not greater than 66 psi (4.6 kg/cm2 ), go to step  14.
  12. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Remove EVAP canister. Disconnect fuel feed pipe from either side of fuel filter. Disconnect fuel return pipe located near EVAP canister. Drain remaining fuel from fuel pipe into container. Connect Fuel Pipe Shutoff Adapter (J-42964-1) onto fuel feed pipe. Open valve on shutoff adapter. Install fuel pressure gauge onto shutoff adapter pressure test connection. Connect flexible fuel hose to chassis fuel return pipe. Place open end of hose into container. Reconnect negative battery cable. Turn ignition on. Using scan tool, command fuel pump on. Monitor fuel pressure with fuel pump running. If fuel pressure is 60-66 psi (4.2-4.6 kg/cm2 ), go to step  23. If fuel pressure is not as specified, go to next step.
  13. Check engine compartment and chassis fuel pipes for restriction. If a restriction is found, go to step  24. If no restriction is found, go to step  21.
  14. If fuel pressure is greater than zero psi, go to next step. If fuel pressure is not greater than zero psi, go to step  17.
  15. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Remove EVAP canister. Disconnect fuel feed pipe from either side of fuel filter. Disconnect fuel return pipe located near EVAP canister. Drain remaining fuel from fuel pipe into container. Connect Fuel Pipe Shutoff Adapters (J-42964-1 and J-42964-2) onto fuel feed and return pipes. Open valves on shutoff adapters. Install fuel pressure gauge onto either shutoff adapter pressure test connection. Reconnect negative battery cable. Turn ignition on. Using scan tool, command fuel pump on. Check for leaks at adapter fittings. Place fuel pressure gauge bleed hose into container. Bleed air from fuel pressure gauge. Using scan tool, command fuel pump on. DO NOT allow fuel pressure to exceed 75 psi (5.3 kg/cm2 ). Slowly close valve on adapter connected to fuel return pipe. Monitor fuel pressure with fuel pump running. If fuel pressure increases to more than 66 psi (4.6 kg/cm2 ), go to step  21. If fuel pressure does not increase to more than 66 psi (4.6 kg/cm2 ), go to next step.
  16. Check for high resistance in fuel system electrical circuits. Check for leaks or restrictions in fuel system. Ensure fuel pump is correct for vehicle application. If a problem is found, go to step  24. If no problem is found, go to step  20.
  17. Turn ignition on. Using scan tool, command fuel pump on. If fuel pump runs, go to next step. If fuel pump does not run, diagnose fuel pump electrical circuit. See appropriate diagnostic procedure under NO START DIAGNOSIS .
  18. Check for appropriate amount of fuel in tank. Check for restrictions in fuel filter, fuel feed pipe and fuel pump strainer. Check for leaks in fuel pump flex pipe. If a problem is found, go to step  24. If no problem is found, go to next step.
  19. Check for fuel leaks in fuel feed pipe between shutoff adapter and fuel sending unit. If a leak is found, go to step  24. If no leaks are found, go to next step.
  20. Replace fuel pump.
  21. Replace fuel pressure regulator.
  22. Replace any leaking or grounded fuel injectors.
  23. Repair restriction in fuel return pipe.
  24. Repair problem as necessary.
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