Fuel Pressure LEAKDOWN Test

NOTE: Perform FUEL PRESSURE LEAKDOWN TEST in conjunction with FUEL PUMP PRESSURE TEST and FUEL PUMP VOLUME TEST . After each repair procedure has been completed, reconnect all components.

Release fuel system pressure. See FUEL PRESSURE RELEASE . Remove air cleaner housing (if necessary) to access quick-connect fuel fittings. Disconnect fuel supply line quick-connect fittings at fuel rail. Connect Fuel Line Pressure Test Adapter (6539) for 5/16" fuel lines, or Fuel Line Pressure Test Adapter (6631) for 3/8" fuel lines, and test port "T" between disconnected fuel supply line and fuel rail.

NOTE: Ensure all fittings on tools and lines are in good condition and are not leaking prior to performing this test or fuel pressure readings may be incorrect.

Connect 0-60 psi fuel pressure test gauge to test port "T" on appropriate Fuel Line Pressure Test Adapter. Start engine and bring to normal operating temperature. Observe fuel pressure test gauge. Fuel system pressure should be 44.2-54.2 psi (305-373 kPa). Shut engine off. Fuel system pressure should not fall below 30 psi (207 kPa) for 5 minutes. Go to next step.
If fuel system pressure falls to less than 30 psi (207 kPa), check fuel injector, check valve inside fuel pump module or fuel tube/line for leaks. To diagnose components and pinpoint fuel system leaks, perform the following tests:
1. Fuel Injector Or Fuel Rail Leakage
  
  Start engine. Clamp off rubber hose portion of Fuel Line Pressure Test Adapter between fuel rail and test port "T" on Fuel Line Pressure Test Adapter. If fuel system pressure does not fall to less than 30 psi (207 kPa) for 5 minutes, fuel injector or fuel rail is leaking. Repair as necessary.
2. Fuel Pump Check Valve, Filter/Regulator Check Valve Or Fuel Tube/Line Leakage
  
  Start engine. Clamp off rubber hose portion of Fuel Line Pressure Test Adapter between vehicle fuel line and test port "T" on Fuel Line Pressure Test Adapter. If fuel system pressure does not fall to less than 30 psi (207 kPa) for 5 minutes, fuel rail and fuel injectors are not leaking. Check fuel lines and tubes for leakage.
If fuel lines and tubes are okay, check electric fuel pump or filter/regulator check valves for leakage. A quick loss of fuel system pressure usually indicates defective check valve in the filter/regulator. A slow loss of pressure usually indicates a defective check valve in the electric fuel pump. Repair as necessary.