'95 XJ 'eating' coils

I have a '95 XJ 4.0 and this thing eats coils. Have owned it for 14 months and have gone through 5 coils. Put a new one on and it last anywhere from 2-3 hours. HELP ! Where do I start looking/checking ???

Dunno '95 I'm Renix guy but ask/look for ignition ballast resistor? The resistor drops voltage during ON but bypasses for starter cranking to keep voltage drop to minimum. Similar to the fuel pump ballast circuit. If it's been bypassed, it could cook the coil in short time as you describe.

But, 1st check your system voltage in case the alternator is malfunctioning and remember I dunno if your model even has an ignition ballast resistor? Hope this helps...

Are you sure it isn't a crank position sensor? That would cause a no spark condition.

Will check the alt this evening . . . have had the CKPS checked and was told it was within 'spec'. Thanks.

Any luck? Im searching for my friend who has a 1995 grand cherokee. His has also been eating coils for the past year. he has bought 5 coils already and cant find the problem.
So far he has checked and replaced some ground wires, and now he is thinking that it might be the PCM. The grand cherokee has the good old inline 6.

Man this sounds like a boat load of defective colis from asia!!!!

Where are you buying these coils???????? Have you tried a different brand or OEM coil. Hell at that rate I would go get one from my new favorite vendor, the JY.:sunshine:

To date have gone through 2 more coils. Have tried coils from all the local auto parts stores - no luck. Seems that Borg-Warner last the longest - have not tried the OEM. I found a site that stated there was a re-wire from the PCM to the coil but it would not print out - I can't find it. Have a friend with a SnapOn 2500 scanner and it shows 'everything' in spec. I, myself, am leaning towards the PCM.

XJXJ: The '95 does not have a ballast resister. I also have an Renix system in an '88 MJ and yes it has a mind of its own.

Thanks for all the replys. . . .

My friend with the coil problem has acutaly bought the OEM along with other high performace coils, right now hes using a Napa coil. It has a one year warranty. :thumbup:

M14/0311 said:

I have a '95 XJ 4.0 and this thing eats coils. Have owned it for 14 months and have gone through 5 coils. Put a new one on and it last anywhere from 2-3 hours. HELP ! Where do I start looking/checking ???

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Have you changed the rotor, cap and plug wires yet? If one or more of them has too high a resistance it could be causing the coil to load up (overload) and look for an alternate path to ground until it finds or makes one, thus burning (shorting) it out. Could also be the ICM (Igniton Coil Modile, electronic) directly under the HV coil) is bad and hiting the coil with too much voltage, thus overloading the coil to burn out. I think the ICM voltage output and input from the CPM(ECU) (with the HV coil removed) can be tested with DMM to see if this is case, while in the run (but do not start mode). As I recall the HV coil has power to the input side and the spark is initiated by ground that low voltage on the coil, which causes a field colapse on the secondary HV side, thus causing the spark.

I would quess that there is bad common supplier of HV coils causing the problem, but I would check and replace (if you have not done so already) the rotor, cap, and HV coils.

I would also find a good, old HV coil, and try it, if it burns up quickly then I would suspect the ICM and or PCM (ECU), (or maybe a shorted wiring harness sending the wrong voltage to coil, like 14 volts instead of 5 volts). I don't recall the coil input volatge, but I am thinking 5 volts for some reason is or was common, so if this is the case a 14 volt signal would cause too high a coil voltage and burn it out.

Thank you for you for lookin into it, i will post up results when he finds out.

IIRC- 9.5-10.0V supply voltage in "run" position is what the coil wants to avoid overheating.
--Shorty