Main Relay (Computer/Fuel System): Testing and Inspection

Relay Test

Fig. 33 Main relay terminal identification:

1. Remove the main relay.
2. Connect the battery positive terminal to the No.4 terminal and the battery negative terminal to the No.8 terminal.
3. Check for continuity between the No.5 and No.7 terminals. If there is continuity, proceed to step 3. If there is no continuity replace relay.
4. Connect the battery positive terminal to the No.5 terminal and the battery negative terminal to the No.2 terminal.
5. Check for continuity between the No.1 and No.3 terminals. If there is continuity, proceed to step 5. If there is no continuity replace relay.
6. Connect the battery positive terminal to the No.3 terminal and the battery negative terminal to the No.8 terminal.
7. Check for continuity between the No.5 and No.7 terminals. If there is continuity then the relay is good, if the fuel pump is still inoperative then proceed to harness testing. If there is no continuity then replace the relay.

Harness Test

1. Make sure ignition switch is in the OFF position. Disconnect the main relay coupler.

Check Yellow/Blue Wire For Battery Power:

2. Connect the positive probe of the circuit tester to the Yellow/Blue wire (1) in the coupler and ground the negative probe of the tester to body ground. If battery voltage is available, proceed to step 3. If there is no battery voltage, check the wiring between the battery and the main relay as well as the No.1 fuse in the engine compartment.

Check Black/Yellow Wire For Battery Voltage:

3. Connect the positive terminal of the test to the Black/Yellow wire (5) of the coupler and ground the negative terminal of the tester to body ground.
4. Turn the ignition switch ON. If battery voltage is available, proceed to step 5. If there is no battery voltage, check the wiring from the ignition switch and the main relay as well as the No.1 fuse.

Check Blue/Red Wire For Battery Power:

5. Connect the positive terminal of the test to the Blue/Red wire (40 in the coupler and ground the negative terminal to body ground.
6. Turn the ignition switch to the START position. If there is battery voltage, proceed to step 7. If there is no battery voltage, check the wiring between the ignition switch and main relay as well as No.10 fuse.

Check For Fuel Pump Operation:

7. Connect a jumper wire between the Yellow/Blue wire (1) and Yellow wire (7) in the coupler.
8. The fuel pump should run. If the fuel pump does not run, check the wiring between the battery and fuel pump and the wiring from the fuel pump to the ground (Black wire).