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Fuel System Diagnosis

  1. Perform diagnostic system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - PRIZM article. Repair any faults identified and go to next step.
  2. Turn ignition off and relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  . Place shop towel around fuel feed hose, and remove quick connect coupling cover of fuel feed hose from fuel feed pipe at fuel rail. Using Fuel Line Quick Connect Separator (J-43178), disconnect quick connect coupling of fuel feed hose from fuel feed pipe. Separate fuel feed hose from fuel feed pipe.
  3. Install Fuel Rail Adapter (J-42982) between fuel feed pipe and fuel feed hose. Connect Fuel Pressure Gauge (J-34730-1A) to adapter. Ensure fuel tank has adequate supply of fuel. Connect negative battery cable. Install scan tool to Data Link Connector (DLC). See SELF-DIAGNOSTICS - PRIZM article. Turn ignition on, with engine off. Using scan tool, command fuel pump on and observe fuel pressure on fuel pressure gauge. If fuel pressure is indicated, go to next step. If fuel pressure is not indicated, go to step  6 .
  4. Using scan tool, command fuel pump on and observe fuel pressure on fuel pressure gauge. If fuel pressure is not 44-50 psi (3.1-3.5 kg/cm2 ), go to next step. If fuel pressure is 44-50 psi (3.1-3.5 kg/cm2 ), go to step  13 .
  5. If fuel pressure is not greater than 50 psi (3.5 kg/cm2 ), go to step  7 . If fuel pressure is greater than 50 psi (3.5 kg/cm2 ), go to step  22 .
  6. If fuel pump control circuit diagnostic procedure was performed, go to step  24 . If fuel pump control circuit diagnostic procedure was not performed, go to FUEL PUMP CONTROL CIRCUIT DIAGNOSIS  .
  7. Remove bottom cushion of rear seat to gain access to fuel pump assembly access panel. Turn ignition on (engine off). Place a listening device on fuel pump assembly. Turn ignition on, with engine off. Using scan tool, command fuel pump on and off, and listen for fuel pump operation. If fuel pump operation is smooth with steady low humming sound, go to next step. If fuel pump operation is not smooth with steady low humming sound, go to step  24 .
  8. Turn ignition off and check fuel pump resistance. If fuel pump resistance is 2-3 ohms at 68°F (20°C), go to next step. If fuel pump resistance is not 2-3 ohms at 68°F (20°C), go to step  24 .
  9. Inspect fuel feed pipe for any kinks, cracks, incorrect routing and/or restrictions. If no problem is found and corrected, go to next step. If problem is found and corrected, go to step  25 .
  10. Remove fuel pump assembly from fuel tank. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. Inspect fuel pump strainer for plugging. If fuel pump strainer is not plugged, go to next step. If fuel pump strainer is plugged, go to step  23 .
  11. Inspect seals and "O" rings between fuel pump, fuel filter and fuel pressure regulator for any cracks, splits, deformation and/or missing components. If no problems are found and corrected, go to next step. If problems are found and corrected, go to step  25 .
  12. Check fuel filter for restriction. If necessary, replace fuel filter. If fuel filter is not replaced, go to step  22 . If fuel filter is replaced, go to step  25 .
  13. Using scan tool, command fuel pump on. Wait for fuel pressure to stabilize, then use scan tool to command fuel pump off. Monitor fuel pressure reading on gauge for 5 minutes. If fuel pressure is 21 psi (1.5 kg/cm2 ) or greater 5 minutes after turning fuel pump off, go to next step. If fuel pressure is not 21 psi (1.5 kg/cm2 ) or greater 5 minutes after turning fuel pump off, go to step  17 .
  14. Road test vehicle with fuel pressure gauge visible from passenger compartment. If fuel pressure decreases during acceleration, cruise or hard cornering, go to next step. If fuel pressure does not decrease during acceleration, cruise or hard cornering, condition may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - CARS article.
  15. Inspect fuel filter and fuel feed pipe for restrictions. If restrictions do not exist, go to next step. If restrictions are located, repair as necessary and go to step  25 .
  16. Inspect fuel system for restricted fuel pump strainer, incorrectly positioned fuel pump pick-up, incorrect fuel pump and/or loose or missing fuel pump or tank baffle. If fuel system is okay, go to step  24 . If any fault was located and repaired, go to step  25 .
  17. Using scan tool, command fuel pump on. While watching fuel pressure gauge, pinch off fuel pressure gauge adapter hose on fuel tank side of gauge. Using scan tool, command fuel pump off. If fuel pressure reading does not hold at 21 psi (1.5 kg/cm2 ) or greater for 5 minutes after turning fuel pump off, go to next step. If fuel pressure reading does hold at 21 psi (1.5 kg/cm2 ) or greater for 5 minutes after turning fuel pump off, go to step  19 .
  18. Check for leaks at base of fuel injectors, fuel injectors and fuel rail. If no repair is required to fix fuel leaks, test fuel injector coils. See FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE IS 50-95°F (PRIZM) in SYSTEM & COMPONENT TESTING - CARS - PRIZM article. If leak is located and repaired, go to step  25 .
  19. Check fuel feed pipe for leaks. If fuel feed pipe is okay, go to next step. If fuel feed pipe is leaking, repair as required and go to step  25 .
  20. Remove fuel pump assembly from fuel tank. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. Inspect seals and "O" rings between fuel pump, fuel filter and fuel pressure regulator for any cracks, splits, deformation and/or missing components. Inspect entire fuel pump circuit for battery voltage at Blue/Black wire at terminal No. 4 of Gray 5-pin fuel pump connector. Inspect ground circuit for less than 5 ohms resistance at terminal No. 5 (White/Black wire) of Gray 5-pin fuel pump connector. If no problems are found and corrected, go to next step. If problems are found and corrected, go to step  25 .
  21. Inspect fuel filter and fuel pump for cracks or leaking seam. If fuel filter and fuel pump are okay, go to next step. If fuel filter and fuel pump are cracked or have a leaking seam, repair as required and go to step  25 .
  22. Replace fuel pressure regulator. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. With fuel gauge installed, start and run engine. With engine running, monitor fuel pressure. If fuel pressure reading is not between 44-50 psi (3.1-3.5 kg/cm2 ), go to step  24 . If fuel pressure reading is between 44-50 psi (3.1-3.5 kg/cm2 ), go to step  25 .
  23. Replace fuel pump strainer. Inspect fuel tank and rest of fuel system for cause of plugged fuel pump strainer. After repair of cause for plugging, go to step  25 .
  24. Replace fuel pump. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. After repair, go to next step.
  25. With fuel gauge installed, start and run engine. With engine running, monitor fuel pressure. If engine starts and fuel pressure reading is between 44-50 psi (3.1-3.5 kg/cm2 ), system is okay. If engine does not start and/or fuel pressure reading is not between 44-50 psi (3.1-3.5 kg/cm2 ), repeat test from step  2 .
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