I have a 95 XJ that I just rebuilt the engine after 297K. The spark just quit one day in the parking lot. Replaced the CPS and TPS, coil tested good as did the CAM sensor. All fuses are good, no melted wires. Maybe a intermittent problem.Anybody have any ideas?

 

Is your Crank Position Sensor an aftermarket, or genuine Mopar part?

The aftermaket stuff is so bad that dead out of the box is not uncommon.


If you got the real deal, consider your Cam Position Sensor, located in the distributor.

It may also be the coil. The coil is pretty easy to test.

https://www.youtube.com/results?sear...testing+a+coil

 

New from Jeep CPS and TPS, coil tested and the only difference was .01 ohms difference in reading. There is zero signal to coil.

 

Feeding the coil will be an ASD fuse and up from that an ASD relay. Both in the PDC fusebox. Have you tested both to see that they are functioning properly, and whether they are getting any voltage during ignition?

 

with the key on all fuses are powered, I also swapped the ASD relay with a known good one. still no signal to coil.
I am on my own so I do not have any help.

 

Since you have swapped the ASD relay already, then you need to confirm that it is actually getting commanded/voltage from the ignition switch.

Also, you said the coil had no signal, but that all fuses were powered when the key was on. If the ASD fuse had power going through it, it should be going to the coil because it is on the asd fuse. So if you truly have voltage at the ASD fuse, but have no voltage as the coil. Then the problem is between the ASD fuse and coil. Either the wiring or the coil.

 

wires all look fine and the coil test good and is only .01 ohms different from new specs.

 

That just means it has proper resistance. Which is good.

But if it isn't getting any voltage during ignition, it won't do any good at all.

The coil is fed from the ASD fuse. You said all the fuses were powered with key on. Like I said before, if that fuse has power with key on, but the coil does not, then the problem is between that fuse and coil (wiring or the coil itself).

Now how did you confirm that the fuses were powered?

 

All I have to work with is small alligator clips 12 volt lights and a meter. Most of the testing I am doing is after dark so I can see the light.

 

You have the tools you need, then. That's good. You should see voltage being fed to the coil any time the key is on. The computer provides ground to the other side when it wants a spark.

So, as Jordan said...


If that checks out good, the problem may be with the computer not providing the ground correctly.

 

still no signal to the coil= no spark
Not sure where to go from here.

 

It turns out the coil has an intermittent failure issue, put a signal to it and it fails, but use a scope and it test good.
Replaced it and all is good

 

Good job. Thanks for the follow-up.