88 XJ, No spark - coil volt/signal ok - stator 2.5v?

After running flawlessly last night, the jeep suddenly wouldnt start this morning. No spark at the plugs or from the coil. I tested the coil for 12v, ground and alternating +5v when starting on the signal wire as all ok, which leads me to suspect the coil has failed. I dont have resistance measurements as a baseline to see if it is shorted. The stator measures 2.5v from the blue wire to the black w/white stripe instead of 5v as my docs say it should read off the distributor, but it does alternate when turning the engine over. Any thoughts? Anyone have coil resistance measurements i can compare to?

thanks, Mike

My book says 0.9-1.4 ohms primary (12 volt) and 7.3-11.1K secondary. This is with the coil seperated from the module.
I'd give you some true numbers, but my spare coil is in my XJ and gone right now.
I don't ever remember seeing a bad Renix XJ coil. Though they did have a series of recalls (TSB) way back when, I guess there was a batch of bad ones.
The module needs a special tester to test it. I remember someone saying there NAPA (or maybe another main chain retailer), had the tester.

How did you test the 5 volt square wave pulse to the module? I've gotten some needle movement with an analoge meter, and some display action with a digital meter, but have never had much luck getting a difinitve pulse signal.
I have both a 88 and a 96.
I've never seen it on a Renix, but 2.5 volts to the sync ring, cam position sensor or whatever it's called, is a sign of a short in the 5 volt supply circuit for various sensors. On my 96, the short was in the CPS, there may be something similiar going on with your Renix. It's difficult to back pin the connector for the cam position sensor with it connected. I've had pretty good results, by pulling the little silicon moisture seals out of the back of the connector and rerouting the cable over the top of something to get a good reading. The cam position sensor actually has little (if anything) to do with ignition (on the Renix), it is for injector timing. But the CPS, crank position sensor sure does.

8Mud,
Good call, it was the CPS. It seems the wire leaned over and melted onto the exhaust manifold when I parked the truck, grounding it out. I taped it up for now, zip tied it out of the way and it started right up. I guess my multimeter test on AC for the wave form was nothing more than fools gold. I figured I could short-cut testing if something was there.

Thanks !

-Mike

If you unroll the extra wire for the CPS, piled on top of the bell housing, you can zip tie the wire to the speedo cable well out of the way of the exhaust and use up all that extra wire just laying around rubbing on things.
I went one step farther and used a piece of slit plastic cable protector and slipped it over the CPS wire and zip tied that to the speedo cable.