Cranks but won't start, also no bus

hear

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2000 TJ, 4.0L auto. Cranks all day, but will not start. Occasionally we'll get a small backfire if we give it some starting fluid.

Was running fine, then died on us one day, had to be towed back & hasn't been able to be started since then.

Verified fuel pressure @ 49psi, 30 mins later was still at 27psi.

Verified spark.

New crank & cam position sensors.

We also get an intermittent no bus on the cluster, but prior to that we did not have any codes. Have verified that the wiring behind the valve cover looks ok.


Not sure where to turn at this point. Any ideas?
 

primetime4

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What brand of sensors did you install and are your other gauges working? When I had this problem it was a crank position sensor and the TJ seems very sensitive to brand here. Would recommend Mopar if you can find one.
 
OP
hear

hear

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I’m sure he bought parts store sensors.

The no bus is weird. I’m at his house now, and the no bus was not present, reader worked fine. Then he put the coil rail back on and the no bus re-appeared.
 
OP
hear

hear

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Well it took me an hour but I got it running. Not sure what it was, however. We cleaned up the battery cables & dug into the sections of the harness (didn’t find anything but if there was a short we may have “cleared it” with all the movement). He replaced the cam & crank sensors, and the coil rail.

We’re working backward to put the old sensors on 1 by 1 to isolate the issue. It’s not the cam, and not the crank. That leaves the rail, some wiring in the harness, or whatever we cleaned up at the battery.
 
OP
hear

hear

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Old coil rail was not the problem. It has to be a short in the harness somewhere. I know what I’m doing tonight.
 
OP
hear

hear

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Last update for a while. We had pulled some of the PCM harness around, didn’t see any wiring issues but it ran fine. Put the wiring back into place and it wouldn’t run again. It did fire up but then immediately would die. Jiggled the wires again, runs fine. 100% it’s a wiring issue.