Fuel Pump: Testing and Inspection
***UPDATED BY TSB #89032 NOV.89OPERATION CHECK:
If a problem is suspected with the Fuel Pump, check to be sure that the Fuel Pump actually runs. It should make a "humming" noise for two (2) seconds when the ignition switch is turned ON. If the Fuel Pump does not make a "humming" noise, check as follows:
1. Jack up car and place jackstands in proper locations.
Fuel Pump Testing:
2. Remove the Fuel Pump cover and disconnect the connector. Make sure ignition switch is turned OFF before disconnecting wires.
3. Check that battery voltage is present at the Fuel Pump connector for two (2) seconds when the ignition switch is first turned ON. Apply positive probe to the yellow wire and negative probe to the black wire.
a. If battery voltage is present replace the Fuel Pump.
b. If there is no voltage, see "COMPUTERIZED ENGINE CONTROLS" for other faults.
COMPLETE PUMP TEST:
If the Fuel Pump does make a "humming" noise but a problem with Fuel Pump output pressure or Fuel Pump check valve is suspected proceed with the following test:
WARNING: Do not smoke during the test. Keep open flames away from your work area. Be sure to relieve fuel pressure while engine is OFF.
1. Attach a pressure gauge to the service port of the fuel filter.
a. Disconnect the negative battery cable.
b. Remove the fuel tank filler cap.
Fuel Filter:
c. Use a box end wrench on the 6mm service bolt at the top of the filter, while holding the special banjo bolt with another wrench.
d. Place a rag or shop towel over the 6mm service bolt and SLOWLY loosen the 6mm service bolt one complete turn.
Pressure Regulator:
e. Remove the service bolt on the top of the fuel filter while holding the banjo bolt with another wrench and attach the fuel pressure gauge.
2. Start the engine. With the fuel pressure regulator vacuum hose disconnected fuel pressure should be:
36 - 41 psi (2.55 - 2.85 kg/cm2)
If fuel pressure is above or below specifications refer to, "FUEL PRESSURE CHECK".
3. Turn the engine OFF.
For the first five (5) minutes fuel pressure should stay at:
30 - 35 psi (2.10 - 2.45 kg/cm2)
For the first ten (10) minutes fuel pressure should drop no more than:
10 psi (.70 kg/cm2)
a. If the fuel pressure drops too fast, go to STEP 4.
b. If the fuel pressure remains stable, fuel pump and fuel pressure regulator are GOOD.
4. Restart the engine, then turn it OFF and lightly pinch the fuel return hose from the fuel pressure regulator.
a. If the fuel pressure remains stable, replace the fuel pressure regulator.
b. If the fuel pressure still drops to fast, replace the fuel pump, as fuel pump check valve is bad.
5. See "COMPONENT REPLACEMENT AND REPAIR PROCEDURES" if component replacement is needed.
6. Disconnect pressure gauge from the service port of the fuel filter and reinstall service bolt. Reattach any hoses that were removed. START engine, check for any leaks.