Bobolink Posted February 28, 2016 Posted February 28, 2016 CPS output 4.5-4.7 VAC. Getting fuel, the injectors are working (so CPS is signaling ECU to fire injectors okay). Yet no spark. Coil impedance is 22.2 ohms across primaries, 4.96K ohms between positive primary to secondary. So coil seems okay. Leaves the dizzy (cam position sensor) or the ICM. Dizzy is indexed. Dizzy was replaced with reman 6-7 years ago. ICM is original Bendix. This was a gradual failure....an intermittent problem with starting, and an occasional incident of stalling (sometimes with an easy restart, sometimes a bit more difficult, but always restarted). These events happened more often when the engine was still cold, with the frequency of occurrence gradually increasing. Then finally it has reached the point where it will not start and there is now no spark at all. With no way that I know of to test either the components on the dizzy or to test the ICM, what would be the opinion of the forum as to which one of these two would the likely culprit? Or is there another component that I have overlooked that might be at fault? My inclination is to replace both. Oh, yes ...... all of Cruiser's pointers have been done at some point over the past few years.
cruiser54 Posted February 29, 2016 Posted February 29, 2016 Try the ICM first as that gizmo in the dizzy is for syncing fuel injector firing and has nothing to do with ignition.
Bobolink Posted March 3, 2016 Author Posted March 3, 2016 Cheesh.....I wish that the Renix ignition was my only problem......dang computer locked up and required a full system recovery to fix....lost all my programs, drivers, emails, everything that didn't come new with the computer..... workin' on the Jeep is a picnic compared to fixin' this! Thanks Cruiser...not that I've got my laptop working again, I'll order me an ICM.
Bobolink Posted March 11, 2016 Author Posted March 11, 2016 Still waiting for a new hard drive so I can get my computer up and running, but the Jeep is good. New ICM and all is well.
cruiser54 Posted March 11, 2016 Posted March 11, 2016 Still waiting for a new hard drive so I can get my computer up and running, but the Jeep is good. New ICM and all is well. We need a conclusive method to check the ICMs. did you replace ICM and coil or just ICM?
Bobolink Posted March 14, 2016 Author Posted March 14, 2016 Just the ICM. Coil checked out with the ohmmeter, not an absolutely conclusive test, but appeared good. Had the ICM replacement not solved the prob, I would've gone on with replacing the coil, too.
cruiser54 Posted March 14, 2016 Posted March 14, 2016 Just the ICM. Coil checked out with the ohmmeter, not an absolutely conclusive test, but appeared good. Had the ICM replacement not solved the prob, I would've gone on with replacing the coil, too. Did you take any ohm readings on the old one versus the new one by chance?
Bobolink Posted March 16, 2016 Author Posted March 16, 2016 Just the ICM. Coil checked out with the ohmmeter, not an absolutely conclusive test, but appeared good. Had the ICM replacement not solved the prob, I would've gone on with replacing the coil, too. Did you take any ohm readings on the old one versus the new one by chance? No, but I can.....give me a day or two. Not that hard to pull and check, and I still have the old one to compare. Not my truck, anymore, by the way. I sold it ... to my brother, of all people. Somebody kick me next time I think about selling to a relative. But I don't mind so much....had it for so many years, just needed something bigger and a little easier on these old bones. Got a Tundra. But little brother knows how well I cared for it, and knows that I know how to work on it. Nobody else has ever been under the hood. He'd had it for about six weeks, but I went down to pick it up and drive it back home, after he said it was giving him some trouble. He lives about 250 miles away. He'll be up to pick it up in a couple weeks.
Bobolink Posted March 28, 2016 Author Posted March 28, 2016 Cruiser, I found no significant differences in ohm readings between the old and new ICMs. At first I thought i was seeing big differences, but as I checked a second and third time, the ohms changed on both units. I don't know if there are capacitors or what that vary the readings, but they did finally settle down on both units, and were very close to the same reading between all combinations of pins. And as I said in the other thread, the new coil fixed the idle problem. Both the ICM and coil were original, 26 years old.
cruiser54 Posted March 29, 2016 Posted March 29, 2016 Cruiser, I found no significant differences in ohm readings between the old and new ICMs. At first I thought i was seeing big differences, but as I checked a second and third time, the ohms changed on both units. I don't know if there are capacitors or what that vary the readings, but they did finally settle down on both units, and were very close to the same reading between all combinations of pins. And as I said in the other thread, the new coil fixed the idle problem. Both the ICM and coil were original, 26 years old. Thanks. I was hoping we could come up with a real life test....
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