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Fuel System Pressure Test (Except SATURN)

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 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. On all models except 2.2L and 2.4L, connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. On 2.2L and 2.4L, install Fuel Pressure Gauge (J-29658-D). This kit modifies fuel pressure gauge so it may be installed in fuel delivery line with quick-connect fittings. On all models, place 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 to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be within specification. See FUEL PRESSURE SPECIFICATIONS (EXCEPT SATURN)  table. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step  12 .
  3. 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 (0.3 kg/cm2 ) in 10 minutes, go to step  10 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm2 ) in 10 minutes, go to next step.
  4. Relieve fuel pressure until pressure is 10 psi (0.7 kg/cm2 ). If fuel pressure decreases more than 2 psi (0.1 kg/cm2 ) in 10 minutes, go to step  19 . If fuel pressure does not decrease more than 2 psi (0.1 kg/cm2 ) in 10 minutes, go to next step.
  5. If fuel pressure is suspected of decreasing during acceleration, cruise or hard cornering, go to next step. If fuel pressure is not suspected of decreasing during acceleration, cruise or hard cornering, go to step  8 .
  6. Inspect in-line fuel filter and fuel feed pipe for restriction. Repair as necessary. After repairs, go to step  24 . If no restriction is found, go to next step.
  7. Remove fuel sending unit assembly. Inspect fuel pump strainer for restriction and correct installation. Check fuel pump flex pipe for leaks, and ensure fuel pump is correct for application. Repair as necessary. After repairs, go to step  24 . If no problem is found, go to step  19 .
  8. Turn ignition off for 10 seconds. Turn ignition on. Fuel pump should run for about 2 seconds. Cycle ignition to obtain highest fuel pressure possible. Note fuel pressure. Start engine. Allow engine to idle until normal operating temperature is reached. If fuel pressure is less than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm2 ), check for intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel pressure is greater than previously noted pressure by 3-10 psi (0.2-0.7 kg/cm2 ), go to next step.
  9. Disconnect vacuum hose from fuel pressure regulator. With engine idling, apply 12-14" of vacuum to fuel pressure regulator. If fuel pressure decreases by 3-10 psi (0.2-0.7 kg/cm2 ), go to step  20 . If fuel pressure does not decrease by 3-10 psi (0.2-0.7 kg/cm2 ), go to step  21 .
  10. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF (EXCEPT SATURN)  . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 65 psi (4.5 kg/cm2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel feed hose. If fuel pressure remains constant, go to step  19 . If fuel pressure does not remain constant, go to next step.
  11. Gradually unpinch fuel feed hose. Using scan tool, pressurize fuel system. Wait for fuel pressure to build. Gradually pinch off fuel return hose. If fuel pressure remains constant, go to step  21 . If fuel pressure does not remain constant, go to step  22 .
  12. If fuel pressure is greater than specification, go to next step. See FUEL PRESSURE SPECIFICATIONS (EXCEPT SATURN)  table. If fuel pressure is less than specification, go to step  15 .
  13. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF (EXCEPT SATURN)  . Disconnect fuel return pipe from fuel rail. Attach flexible fuel hose to fuel rail return outlet passage. Place other end of flexible hose into container. Turn ignition off for about 10 seconds. Turn ignition on. Observe fuel pressure gauge with fuel pump running. Fuel pressure should be within specification. See FUEL PRESSURE SPECIFICATIONS (EXCEPT SATURN)  table. If fuel pressure is within specification, go to step  23 . If fuel pressure is not within specification, go to next step.
  14. Inspect fuel rail outlet passage for restriction. Repair as necessary. After repairs, go to step  24 . If no restriction is found, go to step  21 .
  15. If fuel pressure is greater than zero psi, go to next step. If fuel pressure is zero psi, go to step  17 .
  16. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF (EXCEPT SATURN)  . Place bleed hose into container. Turn ignition on. Bleed air out of fuel pressure gauge. Using scan tool, pressurize fuel system. DO NOT allow fuel pressure to exceed 65 psi (4.5 kg/cm2 ). Excess pressure may damage fuel pressure regulator. Wait for fuel pressure to build. Using scan tool, obtain highest fuel pressure possible. Gradually pinch off fuel return hose. If fuel pressure increases to greater than specification, go to step  21 . See FUEL PRESSURE SPECIFICATIONS (EXCEPT SATURN)  table. If fuel pressure does not increase to greater than specification, go to step  7 .
  17. Check fuel pump electrical circuit. See appropriate diagnostic procedure under NO START DIAGNOSIS  . Repair as necessary. After repairs, go to step  24 . If no problem is found, go to next step.
  18. Remove fuel sending unit assembly. Inspect in-line fuel filter, fuel feed pipe and fuel pump strainer for restrictions. Check fuel pump flex pipe for leaks. Repair as necessary. After repairs, go to step  24 . If no problem is found, go to next step.
  19. Replace fuel sending unit assembly. After repairs, go to step  24 .
  20. Locate and repair loss of vacuum to fuel pressure regulator. After repairs, go to step  24 .
  21. Replace fuel pressure regulator. After repairs, go to step  24 .
  22. Locate and replace leaking fuel injector(s). After repairs, go to step  24 .
  23. Locate and repair restriction in fuel return pipe. After repairs, go to step  24 .
  24. Turn ignition off. Turn A/C system off. On all models except 2.2L and 2.4L, connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure fitting on fuel rail. On 2.2L and 2.4L, install Fuel Pressure Gauge (J-29658-D). This kit modifies fuel pressure gauge so it may be installed in fuel delivery line with quick-connect fittings. On all models, place 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 to obtain highest fuel pressure possible. Observe fuel pressure with fuel pump running. Fuel pressure should be within specification. See FUEL PRESSURE SPECIFICATIONS (EXCEPT SATURN)  table. If fuel pressure is within specification, go to next step. If fuel pressure is not within specification, go to step  11 .
  25. 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 (0.3 kg/cm2 ) in 10 minutes, go to step  10 . If fuel pressure does not decrease more than 5 psi (0.3 kg/cm2 ) in 10 minutes, system is okay.
FUEL PRESSURE SPECIFICATIONS (EXCEPT SATURN)

Application (1) KOEO - psi (kg/cm2 )
2.2L & 2.4L 52-58 (3.7-4.1)
3.0L 40-46 (2.8-3.2)
3.1L, 3.4L & 3.8L 48-55 (3.4-3.9)
3.5L & 4.6L 41-47 (2.9-3.3)
5.7L 55-60 (3.9-4.2)
(1) KOEO is ignition on and engine off.
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