Fuel Pressure: Testing and Inspection

WARNING: Fuel system pressure must be released before a fuel system hose or component is disconnected.

1. Fuel system pressure must be released each time a fuel hose is to be disconnected. Release fuel system pressure.
2. Remove protective cover from service valve on the fuel rail.
3. Connect Fuel Pressure Gauge 0-4799 to fuel rail service valve.

CAUTION: When using the scan tool Fuel System Test, fuel pump relay will remain energized for 7 minutes or until the test is stopped, or until the ignition switch is turned to the OFF position.

4. Place the ignition key in the ON position. Using the scan tool, access actuator test "Fuel System Test." The Fuel System Test will activate the fuel pump and pressurize the system.
- Standard value: 324-343 kPa (47-50 psi)
5. Use the scan tool "Fuel System Test" to pressurize the system. Ensure fuel does not leak from the fuel rail service valve.
6. If pressure is not correct, troubleshoot and repair according to the table below.

Symptom Fuel pressure too low or No fuel pressure in fuel return hose

Probable Cause Followed by Recommended Action
- Clogged fuel filter -- Replace fuel filter
- Fuel leaking to return side due to poor fuel regulator valve seating or settled spring -- Replace fuel pressure regulator
- Low fuel pump delivery pressure -- Replace fuel pump

Symptom Fuel pressure too high

Probable Cause Followed by Recommended Action
- Binding valve in fuel pressure regulator -- Replace fuel pressure regulator
- Clogged fuel return hose or pipe -- Clean or replace hose or pipe

7. Using the scan tool, with the ignition key in the ON position, repeat the "Fuel System Test."
8. Turn the ignition switch off and observe fuel pressure gauge reading. Normal if the reading does not drop within 2 minutes.
- If it does, observe the rate of drop and troubleshoot and repair according to the table below.

Symptom Fuel pressure drops gradually after engine is stopped

Probable Cause Followed by Recommended Action
- Leaky injector -- Replace injector
- Leaky fuel regulator valve seat -- Replace fuel pressure regulator

Symptom Fuel pressure drops sharply immediately after engine is stopped

Probable Cause Followed by Recommended Action
- Check valve in fuel pump is held open -- Replace fuel pump

9. Remove fuel pressure gauge and reinstall protective cover onto fuel rail service valve.