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94 XJ won't start

jonathanlo

NAXJA Forum User
Location
Ontario, OR
When my Jeep troubles started, it would have issues staying running when the motor was hot. I'd pull up to a stop sign and it would die. It would hesitate to start. Then it got worse. I was driving down the highway one day and it just stopped running. It'd cool down for a while and I'd be able to get it started and drive for a few miles. That night, I ended up having to get it towed. I just replaced the fuel pump today to no avail. I'm getting fuel to the rail (disconnected it and sprayed fuel all over myself). Any ideas what this could be? Sensors and such? It'll turn over and it'll fire a cylinder every now and then, but it wont quite catch.
 
Crankshaft position sensor. Common problem with your exact symptoms
 
I concur with Islander, CPS would be my first guess, though it can be other stuff. The CPS fails to send out a good pulse and the PCM stops the spark and the fuel.

The fuel pump relay closes (for few seconds) when the key goes past the run position on the way to the start position and primes/pressurizes the fuel rail. You may get some pressure or a squirt of fuel, but the fuel pump relay won't close again and really turn on the fuel supply, until the PCM gets a good pulse from the CPS.

Sometimes a key test and retrieving the MIL codes will tell you if you have a bad CPS, sometimes it won't. Testing the CPS with an ohm meter can also be iffy, they can test good by the book and still be bad.

If it isn't the CPS it can be something in the ASD relay circuit. I had a bad security module in my ASD circuit that acted just like a CPS problem.

A side note, I had a CPS that would crap out when it got hot. One day I had an idea and dumped a bottle of water on the CPS, cooled it down and XJ started right up. :)

I also had a CPS that was covered in oil, I cleaned the oil off and it has been working since (three years now). I don't really know why the oil would affect it, but it did.
 
I know it's been a super long time since I posted this. I figured this deserved a follow up due to the stupid issue that caused it. After knocking my head against the wall for a long time I found out it was ....... a coil wire!!!!

I guess inside the insulation, the wire had snapped. I'm assuming from the expanding when the engine was operating temp, it would pull the wire apart and kill the engine. After replacing all the BS sensors and the fuel pump, it turned out to be a $20 fix.

Oh well. We live and learn.
 
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