Fuel Pressure: Testing and Inspection

NOTE: To obtain an accurate fuel pressure reading the engine must by running. Basic fuel pump operation can be verified in a no start condition by observing gauge reading while cranking engine. Fuel pressure should be approximately 21 psi (147 kPa).


RELEASE FUEL PRESSURE
1. Remove fuel pump fuse.
2. Start the engine and run it until it stalls.
3. After the engine stalls, crank it for five (5) more seconds.
4. Turn the key "OFF".
5. Reinstall fuel pump fuse.

CHECK FUEL PRESSURE
1. Disconnect fuel filter outlet hose.
2. Connect a fuel pressure gauge between fuel filter outlet and hose.
3. Start engine and idle.
4. Disconnect vacuum hose from pressure regulator.
5. Momentarily pinch return hose closed and observe gauge reading (this checks fuel pump max. output pressure). If not within specification, check all delivery lines and if not pinched or restricted, replace fuel pump.

MAXIMUM FUEL PUMP PRESSURE
Approx. 36 - 50 psi (245 - 343 kPa)

6. Check engine vacuum reading at pressure regulator source hose. If not within specification, inspect for vacuum leak and/or clogged fitting at manifold.

ENGINE VACUUM AT IDLE
More than -19.69 inHg (-66.7 kPa)

7. Reconnect hose and observe gauge reading at idle.

CONTROLLED FUEL PRESSURE AT IDLE
20 - 24 psi (137 - 167 kPa)

8. Disconnect pressure regulator vacuum hose. Fuel pressure should raise.
9. Apply more than -20.5 inHg vacuum to pressure regulator. Fuel pressure should be lower than observed in step 7.
10. If pressure reading was incorrect or did not vary and all previous tests were OK, replace pressure regulator.