Fuel Pressure: Testing and Inspection
1. Disconnect the fuel pump harness connector at the rear of the fuel tank.2. Start the engine and let it run until it stalls then turn off.
3. Disconnect the negative battery cable.
4. Connect the fuel pump harness connector.
5. Remove the upper eye bolt while holding the fuel filter nut securely. Cover the hose connection with a towel in case of splashing from residual pressure.
Remove Upper Eye Bolt From Fuel Filter:
6. Using fuel pressure gauge adapter (part# 03953-24000, 09353-24100, and 09353-24200), install the fuel-pressure gauge to the fuel filter.
Tighten the bolt to 18 - 25 ft.lb (25 - 35 Nm).
Install Pressure Gauge To Fuel Filter:
7. Connect the negative battery cable.
8. Apply battery voltage to the terminal for the fuel pump and check for leaks from the pressure gauge or connections.
9. Disconnect the vacuum hose from the pressure regulator and plug the hose end. Measure the fuel pressure at idle, should be 46 - 49 psi (320 - 340 kPa).
Fuel Pressure Regulator Location:
10. Reconnect the vacuum hose to the pressure regulator and measure fuel pressure again, should be 39 psi (270 kPa).
NOTE: At the completion of steps 8 through 10, prior to turning the ignition off, disconnect the battery power to the fuel pump drive terminal. If the engine stops and NO fuel pressure is observed, refer to COMPUTERS AND CONTROL SYSTEMS to diagnose the fuel pump power supply problem.
11. If the results of the measurements made in steps 9 and 10 are not within the standard values, refer to the symptoms listed below to determine the probable cause and make the necessary repairs before re-testing.
a. Fuel pressure too low:
1. Clogged fuel filter---Replace.
2. Fuel bleeds down to return hose---Replace the fuel pressure regulator.
3. Low pump output pressure---Check for leak in-line or replace fuel pump.
b. Fuel pressure too high:
1. Regulator stuck closed---Replace the fuel pressure regulator.
2. Clogged or bent fuel return hose---repair hose.
c. No difference with or without vacuum connected:
1. Non-responsive regulator---Replace the fuel pressure regulator.
2. Plugged vacuum line or no source vacuum---replace line / repair vacuum source.
12. Stop the engine and check for a change in fuel pressure readings. Pressure should hold for 5 minutes. If the gauge reading drops, observe the rate of drop. Determine the cause according to the following symptoms.
a. Fuel pressure drops slowly:
1. Injector leakage---Identify leaking injector and replace.
2. Regulator is leaking to return line---Confirm and replace regulator.
3. Check valve in the fuel pump is leaking---Replace the pump.
b. Fuel pressure drops immediately:
1. Regulator is leaking to return line---Confirm and replace regulator.
2. Check valve in the fuel pump is open---Replace the pump.
13. At the completion of testing, remove the test equipment and reinstall the upper eye bolt and washer.
Torque to 18 - 25 ft.lbs (25 - 35 Nm).