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Fuel System Pressure Test

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. Perform On-Board Diagnostic (OBD) System Check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK in TESTS W/CODES article. After performing OBD system check, go to next step.
  2. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  . Install Fuel Pressure Gauge (J-34730-1A). Connect negative battery cable. Using scan tool, command fuel pump on. Observe fuel pressure with fuel pump running. Fuel pressure reading should be 44-50 psi (3.1-3.5 kg/cm2 ). If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step 4).
  3. If fuel pressure is greater than 44-50 psi (3.1-3.5 kg/cm2 ), go to step 24). If fuel pressure is less than 44-50 psi (3.1-3.5 kg/cm2 ), go to step 12).
  4. If fuel pressure is present, go to step 6). If fuel pressure is not present, go to next step.
  5. Diagnose fuel pump electrical circuit. See FUEL SYSTEM ELECTRICAL CIRCUIT under NO START DIAGNOSIS  . After repairs, go to step 26). If fuel pump electrical circuit is okay, go to step 25).
  6. Remove fuel filler cap. Using scan tool, command fuel pump on. Listen for operation of fuel pump. Fuel pump should operate with a smooth and steady low humming sound. If fuel pump operates as specified, go to next step. If fuel pump does not operate as specified, go to step 25).
  7. Using a DVOM, measure resistance between fuel pump connector terminals (pump side). Resistance should be 0.2-3.0 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, go to step 25).
  8. Check fuel feed pipe for kinks, cracks, restrictions or incorrect routing. Repair as necessary. After repairs, go to step 26). If fuel feed pipe is okay, go to next step.
  9. Remove fuel sending unit assembly. Check for a plugged fuel pump strainer. If fuel pump strainer is plugged, go to step 23). If fuel pump strainer is okay, go to next step.
  10. Check "O" rings and seals between fuel pump, fuel filter and fuel pressure regulator for cracks, splits, deformities or if missing. Repair as necessary. After repairs, go to step 26). If "O" rings and seals are okay, go to next step.
  11. Check for restricted fuel filter. Replace as necessary. After repairs, go to step 26). If fuel filter is okay, go to step 22).
  12. Using scan tool, command fuel pump on. Wait one minute for fuel pressure to stabilize. Monitor fuel pressure. If fuel pressure remains stable at 21 psi (1.5 kg/cm2 ) or greater for 5 minutes after fuel pump turns off, go to next step. If fuel pressure does not remain stable as specified, go to step 17).
  13. If it is suspected that 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, see TESTS W/O CODES article.
  14. Check for restrictions in fuel filter and fuel feed pipe. If a restriction is found, go to next step. If fuel filter and fuel feed pipe are okay, go to step 16).
  15. Repair restriction as necessary. After repairs, go to step 26).
  16. Check for restriction in fuel pump strainer, position of fuel pump pick-up, and if fuel pump is correct pump for vehicle. Repair as necessary. After repairs, go to step 26). If strainer, pick-up and fuel pump are okay, go to step 25).
  17. Using scan tool, pressurize fuel system. Pinch fuel feed hose at fuel pressure gauge and check fuel pressure. If fuel pressure remains stable, go to step 19). If fuel pressure does not remain stable, go to next step.
  18. Check for leaks at base of fuel injectors, injectors or fuel rail. Repair as necessary. After repairs, go to step 26). If no leaks are found, check fuel injectors. See SYSTEM/COMPONENT TESTS article.
  19. Check for leaks in fuel feed pipe. Repair as necessary. After repairs, go to step 26). If fuel feed pipe is okay, go to next step.
  20. Remove fuel sending unit assembly. Check "O" rings and seals between fuel pump, fuel filter and fuel pressure regulator for cracks, splits, deformities or if missing. Repair as necessary. After repairs, go to step 26). If "O" rings and seals are okay, go to next step.
  21. Check for cracks or a leaking seam in fuel filter and fuel pump. Replace as necessary. After repairs, go to step 26). If fuel filter and fuel pump are okay, go to next step.
  22. Replace fuel pressure regulator. Start and run engine. Monitor fuel pressure while engine is running and with engine off. If engine starts and runs with fuel pressure within normal range, go to step 26). If engine does not start, or fuel pressure is not within normal range, go to step 25).
  23. Replace faulty fuel pump strainer. Check fuel system for cause of plugged fuel pump strainer. Repair as necessary. After repairs, go to step 26).
  24. Replace fuel pressure regulator. After repairs, go to step 26).
  25. Replace fuel pump. After repairs, go to step 26).
  26. Attempt to start and run engine. Monitor fuel pressure while engine is running and with engine off. If engine starts and runs with fuel pressure within normal range, system is okay. If engine does not start, or fuel pressure is not within normal range, go to step 2).
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