Fuel Pressure Leak Down Test

Abnormally long periods of cranking, to restart a hot engine that has been shut down for a short period of time, may be caused by:

^ Fuel pressure bleeding past the fuel pressure regulator.
^ Fuel pressure bleeding past the check valve in the outlet end of the fuel tank mounted fuel pump.

Pressure Regulator And Vacuum Hose:

1. Remove protective cap at fuel rail test port. With the engine off connect an accurate 0-689 kPa (0-100 psi) fuel gauge to the pressure test port fitting on the fuel rail. The fitting on the pressure tester must be in good condition and free of any leaks before performing this test.

2. Start the vehicle and let engine idle. Check fuel pressure reading on gauge. Fuel pressure should be within specifications. Refer to Fuel System Pressure Test.

3. Shut engine off. Observe and record fuel pressure reading on gauge. Leave fuel pressure gauge connected. Allow engine to set for 30 minutes and then compare the fuel pressure reading on the gauge with the reading taken when engine was shut down. A pressure drop of up to 138 kPa (20 psi) within 30 minutes is within specifications.

^ If the fuel pressure drop is within specifications, the fuel pump outlet check valve and fuel pressure regulator are both operating normally. Test completed.

^ If fuel pressure drop is greater than 138 kPa (20 psi), it must be determined if this drop is being caused by (in-tank mounted) fuel pump outlet check valve or fuel pressure regulator. Proceed to next step.

4. Release the fuel system pressure from fuel system. Refer to Fuel Pressure Release Procedure. Service and Repair

5. Disconnect both fuel tubes (lines) at fuel rail near fuel pressure regulator.

Adapter Tools - Typical Connections:

6. Connect Fuel Line (Tube) Pressure Test Adapter Tool number 6631 (3/8 in.) between the disconnected fuel supply line and fuel rail.

7. Connect Fuel Line (Tube) Pressure Test Adapter Tool number 6539 (5/16 in.) between the disconnected fuel return line and fuel rail.

8. Start engine. Observe and record fuel system pressure.

9. Shut engine off.

10. Clamp off the rubber hose portion of adapter tool number 6539 connected to the fuel return line. Allow engine to set for 30 minutes.

^ If pressure has dropped more than 138 kPa (20 psi) in 30 minutes, pressure is bleeding past the (in-tank mounted) fuel pump outlet check valve. Replace Fuel Pump Module assembly. Refer to Fuel Pump Module removal and installation.

^ If pressure drop is within specifications, proceed to next step.

11. Clamp off the rubber hose portion of adapter tool number 6631 connected to the fuel supply line. Allow engine to set for 30 minutes.

^ If pressure has dropped more than 138 kPa (20 psi) in 30 minutes, pressure is bleeding past the fuel pressure regulator. Replace fuel pressure regulator. Refer to Fuel Pressure Regulator removal and installation.