help!!!! 96 Xj wont start

[aw12345]

Find the signal wire coming from the crank sensor going to the ecm. Back probe it at the ecm connectorwith the key on turn the engine over slowly, you should see 5 volts then when you turn the engine over some more it should go to 0 volts then to 5 volts and so on. If it does that then the crank sensor is sending a signal to the ecm. Easiest test would be to borrow a OBD2 scanner from somebody, look at the data stream while cranking, if you get a rpm reading of say 200 rpm crank sensor is good and the ASD relay should activate. If it reads 0 rpm the ecm is not seeing a crank signal so no fuel pump or asd relay gets activated.

[kirkandsylvia]

Thank you Russ for the additional info for testing. I will retest the crank position sensor wiring too Art. But this will all have to wait for some time. My shoulder surgery has been scheduled for today at noon and I will be out of service for several weeks before I can do any physical labor. Not exactly what I was planning on, but the surgery needs to happen. So....my ongoing jeep saga is going to be put on hold.....kinda like a season finale that will start up in the fall. Thank you all for your continued support and suggestions and Russ, again, many thanks for spending the day here Monday.

[6spdYJ]

Is it throwing the code before cranking the starter? Have you verified that the camshaft position sensor is getting flagged? If it's in the distributor - and by chance the distributor isn't turning - it won't send the signal. If it's at the timing gear - and by chance the cam is not turning - it won't send the signal. I don't know where yours is located, but it's worth looking into.

[Russ Chung]

Ted,

If we clear the code and turn on the ignition, it does not throw a code until you crank the engine.
If we clear the code and turn on the ignition but do not crank the engine, the computer still turns off the ASD relay.
We verified that the distributor is turning. At the time, I did not know that the signal circuit should change from 5 volts to 0 volts and back to 5 volts when the window passes the sensor so we did not look for that voltage change. That will be one of the first things to check when Kirk recovers from his shoulder surgery.

[dr.dirty]

Just for giggles Id look at the pressure regulator.... I would have been willing to bet good money that my issue was electrical and all signs pointed to electrical and after lots of wasted $$$ and time it ended up being the pressure regulator.

[aw12345]

Just beg borrow or steal a OBD2 scanner look at the data stream while cranking. It will tell you what you need to know

[peteyg]

I know this is a little old, and hopefully you have fixed your problem, but I wanted to chime in.

My '96 XJ has been having PCM issues for about a year and a half. The Jeep will die randomly, throw weird codes, etc. I have replaced EVERYTHING. After troubleshooting this thing to death, I can say with CERTAINTY that your problem is one of two things:

1. One of the wires in the circuit you highlighted yellow is shorted (my bet would be on the front O2 sensor wire that goes down really close to the exhaust manifold or the rear O2 sensor wire), or

2. Your PCM connections are shot. Try this: Zip tie the connectors to the PCM and get them as tight as possible. Bad PCM connections can be caused by a loose connector (suspect the gray one...it has the ASD controller circuit in it), or bad solder joints inside the PCM on the circuit board.

Also, if one of the sensor wires are shorted, Fuse 20 in the PDC under the hood is blown.

It is NOT:

The CPS or CPK sensors.
The MAP Sensor
Any sensor at all, actually.
The Fuel Pump
The ASD Relay
The Fuel Pump Relay

It could be:

The coil (my PCM was shorting out and blowing the coils at an alarming rate). A blown coil is a symptom, not a cause of the no-start problem.

Good luck!