No Fuel No Spark - 1993 ZJ 4.0L 4WD AW4 TRANS. -
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post #1 of 2 Old 03-08-2020, 06:47 PM Thread Starter
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No Fuel No Spark - 1993 ZJ 4.0L 4WD AW4 TRANS.

No Fuel No Spark - 1993 ZJ 4.0L 4WD AW4 TRANS.

1993 ZJ 4.0L 4WD AW4 TRANS., VIN: 1J4GZ58S6PC555450 PCM part # 56027811

I need a Jeep electrical guru here.

I got this Jeep from a relative to keep & drive or fix & sell. I’ve never driven it. One owner, family commuter in decent shape. No mods. I have 1 key, no fobs. Unsure if it ever had a fob.
Jeep cranks but no fuel or spark. Check engine light on dash does go out after key is on for a bit; I haven't deciphered codes yet doing the “key dance”. No security lights on dash. I have most tools except any type of scanner.

In a nutshell: ASD and fuel relays are not switching (I pulled their covers off and watched them with key on/off). But when I manually test them with battery power, they are working just fine. Each relay has 12v with key off and 12v at the Lt. Blue/Rd wires when key is on. I’ve cleaned all grounds and ignition system connections with a brush and reassembled.

When the coil is unplugged and the key is on the plug has 11.45v at Gray wire and the Dk Green/Black wire “pulsates” when cranking. With the key on, voltage immediately disappears when it is plugged into the coil. Thinking the coil was at fault, I installed a new one, with no success.

Crankshaft Position Sensor - ohms measure exactly as a new one. Has 0.5 ohms between B and C contacts. Has 9 volts supplied to it and pulses during cranking.

Camshaft Position Sensor – White/Bk wire is 9.35V with key on. Black/blue & Gray/Blk wires have continuity.

02 sensor is installed and wires are visually damage-free.

#51 pin Pink wire at PCM has no power with key on or off or cranking. I also back-probed #51 and put my other end of multi-meter on the ASD and Fuel relay contacts. It has 6,950 ohms with relay contacts with key off. With key on, it has 7,790 ohms and 7,570 ohms with the other key switched wires at the relays. Is the Pink wire a PCM-controlled ground?

#57 pin Dk Green/Black wire at PCM has erratic voltage: very low with key off and on and cranking. Then cycle the key off then back to on and volts go to ~7 volts.

Side notes:

1.) fuel tank leaks somewhere at top when I filled it full. Rear area smells of strong gas.
2.) Also, left rear door lock does not function with power switches. Must be manual locked/unlocked. The lock mechanism (actuator/servo) runs continuous if I hold the lock button in “lock” or “unlock”. None of the other doors do that.
3.) There is a 2-wire plug tied into the starter harness. It is about 8 inches long, Brown/Gray and black wires, and hangs right by the oil filter. I don't see anywhere where it goes. Could this be for a manual transmission jeep?

What on earth is going on here? Harness short, PCM failure, TCM failure? Security system? Could a fuel/vapor leak be preventing the system from running normal? Something I’m missing?

I appreciate any/all help.

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post #2 of 2 Old 04-04-2020, 03:43 AM
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Did you ever find out the problem having b the same issue with my 94
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