Cherokee 4WD L6-242 4.0L VIN S MFI (1992)
Main Relay (Computer/Fuel System): Testing and Inspection
RELAYS-OPERATION AND TESTING
The following operations/tests apply to these relays only:
Automatic Shutdown (ASD), Fuel Pump and Ballast Bypass. For operations/tests on all other relays refer to the appropriate test.
OPERATION
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The relay terminal numbers can be found on the bottom of the relay.
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Terminal number 30 is connected to battery voltage and can be switched or B + (hot) at all times.
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Terminal number 87A is connected (a circuit is formed) to terminal 30 in the de-energized (normally OFF) position.
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Terminal number 87 is connected (a circuit is formed) to terminal 30 in the energized (ON) position. Terminal number 87 then supplies battery
voltage to the component being operated.
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Terminal number 86 is connected to a switched power source.
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Terminal number 85 is grounded by the Engine Controller.
TESTING
1. Remove relay before testing.
2. Using an ohmmeter, perform a resistance test between terminals 85 and 86. Resistance value (ohms) should be 75 ±5 ohms for resistor equipped
relays.
3. Connect the ohmmeter between terminals number 87A and 30. Continuity should be present at this time.
4. Connect the ohmmeter between terminals number 87 and 30. Continuity should not be present at this time.
5. Use a set of jumper wires (16 gauge or smaller). Connect one jumper wire between terminal number 85 (on the relay) to the ground side (-) of a 12
Volt power source.
6. Attach the other jumper wire to the positive side (+) of a 12V power source. Do not connect the jumper wire to relay at this time.
CAUTION: DO NOT ALLOW THE OHMMETER TO CONTACT TERMINALS 85 OR 86 DURING THESE TESTS. DAMAGE TO
OHMMETER MAY RESULT.
7. Attach the other jumper wire (12V +) to terminal number 86. This will activate the relay. Continuity should now be present between terminals
number 87 and 30. Continuity should not be present between terminals number 87A and 30.
8. Disconnect jumper wires from relay and 12 Volt power source.
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If continuity or resistance tests did not pass replace relay. If tests passed, refer to Wiring Diagrams for additional circuit information.
