Fuel Pressure Leak Down Test

NOTE: If long cranking periods are experienced trying to restart a hot engine after a brief shut down, the fuel system pressure may be bleeding off past the fuel pressure regulator, or past the fuel pump outlet check valve.
1. Connect a 0-689 kPa (0-100 psi) pressure gauge in line before the pressure regulator.
2. START the engine and allow it to idle, then note the fuel pressure.
^ If the pressure is within specification, proceed to step 3.
If the pressure is outside of specifications, proceed to Fuel System Pressure Test.
3. STOP the engine, noting the gauge reading. Allow the engine to sit, with key OFF for 30 minutes, then recheck the fuel pressure gauge. A pressure drop of 0-138 kPa (20 psi) from the specified operating pressure is normal, and no further fuel pump testing is necessary. If the fuel pressure drop is greater than that specified, proceed to step 4.
4. START the engine and allow it to idle. Simultaneously pinch the fuel return hose, and STOP the engine. Note the fuel pressure reading. Allow the engine to sit for 30 minutes, with the fuel return line pinched, and recheck the pressure reading.
^ If the pressure has dropped 0-138 kPa (20 psi) or less, replace the fuel pressure regulator.
^ If the pressure drop still exceeds the specified amount, the fuel pump check valve or one of the fuel pump hoses is leaking inside the fuel tank, and the pump/sending unit will need to be removed from the tank and inspected. If there are no visible problems replace the fuel pump.