lawdog

Ok if there are any threads im missing on this please point me in the right direction. My 89 Cherokee burned up my ICM the other day and I went and bought another one. I put the new one in the jeep and had the alternator checked and everything passed. I started the jeep and it ran great for about 5 mins. Then it stopped. Had the bran new ICM checked and it had burned out to. What am I missing. Those things are $115 a pop. any help would be great. Thanks

freegdr

your going to have to check for shorts in power source to it with wiring diags and test light or volt meter

tjwalker

Gotta tell you that this may be a tough one.

Something is shorting out your computer and finding out why is going to take a schematic, a meter, and the ability to use both of those things.

Obviously, no new ICM until you are SURE you have found the problem.

Good luck.

freegdr

im done all ready lol

freegdr

law dog you do own a manual

lawdog

lol yea i got a manual. I was hoping it wouldnt come to that but oh well. thanks and i will let you no if i come up with anything.

freegdr

good luck

lawdog

ok so i jumped to conclusions. I had my new ICM tested and they say its fine. I checked for power from the coil to the distributer and its there. Then I checked for spark..... I dont have any. I pulled off the Spark plug wire and had my wife turn the jeep over. I tested the end of the plug wire and i have power but it is very weak, not enough to make the plugs spark. I put new distributer cap and rotor button on the same time i changed the ICM. Any Ideas. oh and it has a new CPS about 3 months ago. Thanks

tjwalker

Have you actually tested the ignition coil for primary and secondary resistances per manual? That is the only way to verify the coil.

For a weak spark, the coil is always suspect.

lawdog

Ok so its fixed. I just wanted to give a quick update. At first I thought it was the coil but I tested the coil per the book and it checked out just fine. So then I had my ICM tested and it failed on SATURATION and according to the machine that is what tells the coil how much voltage to send to the distributor. Anyway I changed the ICM and it started and ran great for about 5 min then shut off. I thought the ICM must have burned up again but upon further investigation it ended up being the coil this time. Now I’m not a mechanic by any means but the best I can figure is both the ICM and the Coil were on there last leg and when I put a new ICM in and the coil started getting the right amount of power it finally conked out too. Thanks for all the help guys your all great!!!!!