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Fuel System Pressure Test

WARNING: Begin fuel system trouble shooting and diagnosis with fuel system pressure test. Relieve fuel system pressure before disconnecting any components or installing fuel pressure gauge.
  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  . After performing OBD system check, go to next step.
  2. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  . Connect Fuel Pressure Gauge (J-34730-1A) to fuel pressure connector. Turn ignition on. With ignition on and engine off, pressure should be 41-47 psi (2.9-3.3 kg/cm2 ) and should hold steady.
  3. If pressure is within specification and holds, go to next step. If pressure is not within specification or within specification but does not hold, go to step 9).
  4. If fuel pressure is suspected of dropping off during acceleration, cruise or hard cornering, go to next step. If fuel pressure is as specified, go step 7).
  5. Inspect fuel filter and fuel supply line. Repair or replace as necessary. After repairs, go to step 27). If fuel filter and fuel supply line are okay, go to next step.
  6. Remove fuel sending unit from fuel tank. Inspect fuel pump strainer for restriction, position of fuel pump strainer, fuel pump noise dampener or verify if fuel pump is of right application. Repair or replace as necessary. After repairs, go to step 27). If no problems are found, go to step 20).
  7. Start engine. Warm engine to normal operating temperature. Allow engine to idle. Observe fuel pressure gauge. Fuel pressure should drop 3-10 psi (.2-.7 kg/cm2 ). If fuel pressure drop is as specified, see TESTS W/O CODES article. If fuel pressure drop is not as specified, go to next step.
  8. Disconnect vacuum hose to fuel pressure regulator. With engine at idle, apply 12-14 Hg. vacuum to fuel pressure regulator, using a vacuum pump. Fuel pressure should drop 3-10 psi (.2-.7 kg/cm2 ). If fuel pressure drop is as specified, go to step 21). If fuel pressure drop is not as specified, go to step 22).
  9. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  . Connect Fuel Pressure Gauge (J-34730-1) to fuel pressure connector. Install Fuel Pipe Shut-Off Adapter (J-37287) between fuel feed line and return line. Open valve on shut-off adapter. Pressurize fuel system by using scan tool. Bleed air out of fuel gauge. Wait for pressure to build up. Close valve in fuel shut-off adapter. If fuel pressure remains constant, go to next step. If fuel pressure does not remain constant, go to step 11).
  10. Remove fuel sender unit from fuel tank. Inspect fuel pump pulse dampener. If dampener is leaking, go to step 23). If dampener is okay, go to step 20).
  11. Open fuel shut-off adapter valve. Pressurize fuel system using scan tool. Wait for pressure to buildup. Close shut-off valve. If fuel pressure remains constant, go to step 22). If fuel pressure does not remain constant, go to step 24).
  12. If fuel pressure is greater than specification, go to next step. If fuel pressure is as specified, go to step 16).
  13. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF. Disconnect fuel return line from fuel rail. Attach a piece of fuel hose to return line and place in a container. Turn ignition off for about 10 seconds. Turn ignition on. Observe fuel pressure with fuel pump operating. Fuel pressure should be 41-47 psi (2.9-3.3 kg/cm2 ). If fuel pressure is as specified, go to step 25). If fuel pressure is not as specified, go to next step.
  14. Inspect fuel rail return/outlet passage for restriction. If restriction is present, go to step 27). If restriction is not present, go to next step.
  15. Remove fuel pressure regulator. Inspect regulator filter screen for restriction. If restriction is found, go to step 27). If restriction is not found, go to next step.
  16. If fuel pressure is not present, go to step 18). If fuel pressure is less than 41 psi (2.9 kg/cm2 ), go to next step.
    CAUTION: DO NOT allow fuel pressure to exceed 60 psi (4.2 kg/cm2 ).
  17. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF  . Connect Fuel Pressure Gauge (J-34730-1). Install Fuel Pipe Shut-Off Adapter (J-37287) between fuel feed line and return line. Open valve on shut-off adapter. On all engines, pressurize fuel system using scan tool. Bleed air out of fuel gauge. Wait for pressure to build up. Slowly close valve on fuel shut-off adapter. If fuel pressure increases to greater than specification, go to step 22). If fuel pressure does not increase to greater than specification, go to step 6).
  18. Check fuel system. See FUEL SYSTEM TEST under A-3, NO-START DIAGNOSIS  . If fuel pump circuit is faulty, go to step 27). If fuel pump circuit is okay, go to next step.
  19. Inspect fuel filter for obstruction, fuel supply line for restriction, fuel pump strainer for correct installation, fuel pump strainer for obstructions or fuel pump pulse dampener for leaks. Repair or replace as necessary. After repairs, go to step 27). If problem was not found, go to next step.
  20. Replace fuel pump.
  21. Locate and repair vacuum leak to fuel pressure regulator.
  22. Replace fuel pressure regulator.
  23. Replace fuel pump pulse dampener.
  24. Locate and replace and leaking fuel injector(s).
  25. Locate and correct restriction in fuel return line.
  26. Remove and discard fuel pressure filter screen.
  27. Repair problem as necessary. Using scan tool, clear any DTC(s) stored.
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