Fuel Pump Relay: Testing and Inspection

If one of the fuel pumps will not energize while attempting to start the engine perform the following test.

NOTE: a. It will first be necessary to determine which bank of cylinders is not being provided with fuel. DME system 1 (CYL. 1-6) or DME system 2 (CYL. 7-12).
b. All terminal numbers refer to numbers stamped on the relay socket and not the relay body.

1. Check the fuel pump circuit fuse in the power distribution box. Replace the fuse as necessary. If the fuse tests OK continue.

^ Fuel pump for DME control 1 (fuse 23)
^ Fuel pump for DME control 2 (fuse 24)

2. Remove the fuel pump relay and bridge terminals 7 and 2 of the fuel pump relay socket with a fused jumper.

^ The fuel pump should run. If the fuel pump does not run check the circuit from terminal 2 of the fuel pump relay socket to the fuel pump. If the circuit is OK refer to FUEL PUMP for testing the fuel pump. If the fuel pump test OK continue.

3. Remove the fused jumper and test voltage at terminal 7 of the fuel pump relay socket.

^ Reading should be 12 volts. If not check the circuit to battery positive for opens.

4. Test for ground at terminal 6 of the fuel pump relay socket.

^ If ground is not present test for open circuit to ground point under the plastic cover next to the E Box (control unit box).

5. Test voltage at terminal 4 of the fuel pump relay socket while cranking the engine.

^ Reading should be > 10 volts. If not check circuit from fuel pump relay socket terminal 4 to the start relay socket terminal 2 for opens. If the circuit is OK refer to ELECTRICAL AND ELECTRONIC DIAGRAMS for checking the starter relay, ignition switch and A/T range switch.

6. Test for voltage at terminal 5 of the fuel pump relay socket.

^ With the ignition on reading should be 12 volts. If not check for open circuit between terminal 5 of the fuel pump relay socket and terminal 2 of the DME main relay socket. If the circuit is OK refer to COMPUTERIZED ENGINE CONTROLS for testing the DME main relay and control unit.

7. While cranking the engine test for pulsed ground at terminal 1 of the fuel pump relay socket. If a pulsed ground signal is not present check the circuit from terminal 1 of the fuel pump relay to terminal 1 of the DME control unit for opens or short. If the circuit tests OK refer to COMPUTERIZED ENGINE CONTROLS for testing the DME control unit.

NOTE: Terminal 1 of the fuel pump relay socket receives the same ground signal as the primary side of the ignition coil from the DME control unit. The signal is interpreted as RPM input.




^ If all circuits tests are OK replace the fuel pump relay.