no spark problem

If you are getting no power to the coil that means something is keeping your ASD relay open, the usual suspect is the CPS.

When you turn the key to run without turning it to start, do you have a CEL light?

Have you tried the key test to see if you have any stored codes?

Do you have a security system that is tied into your key fob door opener?

Is yours an early 96 or a late 96? My early 96 has many 95 parts in it, which sometime makes it interesting guessing which parts I need..

I guess the new cps could a bad one? I've been thinking that it might be. And there is a check engine with key on. I had parts store put on there cheap code reader came back as O2 sensor - temp. Sensor strange thing is they all said high voltage with each code? There's no alarm not sure of the month it was made. Thanks 8mud

check the ground wires at the stud where the oil dipstick tube is. a broken one there will cause a cts and o2 high code

Thanks guys found out the ignition module is bad! Which is in the Ecu. !!!!! So time to break out a couple hundred! Again .. J.E.E.P

um... if you are spending a couple hundred on an ECU I have a tip for you, try the junkyard.

pretty rare.

chances are high that that isn't the problem.

Be sure to let us know when you replace it if it fixed it.

Digger87 any other ideas? Thanks

Well, first off I would need to know how you came to the conclusion that the ECU was bad?
What specific tests were done to determine this?

I'm not saying your diagnosis is incorrect, just that ECU's failing on 4.0s are really rare.

Snap on scanner said and a lot of testing. Only thing left there's the proper voltage where it should be all sensors are good grounds goods fuses etc. etc.

Well i got a 97 Ecu put it in fired right up! !!!!

Right on man!

Well the ecu worked but...... not for long seem to be fried again? Same problem as before! ? So i got to reading on it and it seems i get to high of voltage to ecu which fries it? I seen this web site http://www.ehow.com/list_7451463_causes-jeep-pcm-failure_.html can somebody explain it what they mean on the voltage part? Thanks again

I know this thread is a little old, but ive got a related question.

I suspect the cps is bad on my rig(97 xj 4.0)

problem is, ive got no power to the coil, which means no spark of course. ive jumped the coil directly off the battery and it fires right up. when the key is on, I can hear the relays actuate when I plug and unplug the cps. ive got fuel pressure. the rig runs flawlessly once I hot wire the coil. ive had cps problems before so im going to replace it relatively soon anyways.

any ideas?

Interesting.

On HO rigs, the ASD relay and fuel pump relay are kept off until the ECU sees a valid CPS signal. Then they are turned on and the engine runs normally. The ASD relay runs the O2 sensor heaters, part of the ECU (but not all of it), the alternator field winding, the ignition coil, the fuel injectors, and a few other things. So when you jump the coil off the battery you're actually powering a lot of circuits, not just the coil.

My guess is one of two things has happened. One, the ASD relay has worn out - try swapping it with another one to check that. Two, your downstream O2 sensor wiring has come loose from the transmission tunnel and dropped onto the rear driveshaft, worn through, and shorted out. This will usually blow the blue (15 amp? 20 amp? can't remember) mini fuse somewhere near the middle of the PDC that powers... you guessed it... all that stuff I listed under ASD relay. Check that fuse (and any others you feel like checking, if you get bored) and if it's blown, check the O2 sensor wiring and repair as necessary to prevent it shorting out again.