Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSJEEP1987CHEROKEE LIMITEDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEM4.0L MPI SYSTEMDIAGNOSIS & TESTINGCOMPONENT TESTINGRELAYS - GENERAL TESTING
1987 Jeep Cherokee Limited
Relays - General Testing
1987 Jeep Cherokee LimitedSECTION Relays - General Testing
- The relays used on the 4.0L engine are all of the same basic construction and design. Terminal No. 30 is usually connected to battery voltage ("switched" or battery positive at all times). Terminal No. 87A is connected to terminal No. 30 in de-energized position.
- Terminal No. 87 is connected to terminal No. 30 in the energized position. This connection supplies battery voltage to the operated device.
- Terminal No. 86 is connected to the electromagnet of the operated device; usually through a "switched" power source. Terminal No. 85 is connected to the electromagnet of the operated device; usually grounded through a switch or the ECU.NOTE: Not all relays have battery voltage applied at terminal No. 1. Some may have battery voltage applied at terminal Nos. 87 or 87A. Check design of relay before testing.
- When testing relays, there should be continuity between terminal Nos. 87A and 30 when relay is in de-energized position. Resistance between terminal Nos. 85 and 86 should be 70-80 ohms for resistor-type relays and 81-91 ohms for diode-type relays.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.