Fuse #10 ECM IGN blows intermittently 96 Blazer 4x4
 

I have a 96 Blazer 4x4 (4.3L W engine). I do have the factory service manuals with all the info.

I did recently replace the distributor as the original one had a broken lug for holding down the cap. New cap and rotor as well. Did the CASE relearn using the manual procedure outlined somewhere else here. Put about 400 miles on it since then and it ran perfect. Until now....

I have been having an intermittent problem Fuse #10 "ECM IGN" (20A fuse) blowing. When it blows, engine will quit (of course) stranding me a couple times. Only runs a few minutes now, but since its intermittent its hard to find the culprit, clearly something is shorting to ground.

Looking for knowledge on commonly failing parts in this circuit.

The circuit powers the following:
1. VCM (aka ECM)
2. Fuel Injector system
3. Ignition Coil
4. Electronic Ignition Control Module
5. Crankshaft Position Sensor

Problem is I can really can't disconnect any of them and still have the engine run to get the fuse to blow.

While the problem "could" be downstream from the VCM, I am hoping not.

Are any of these common to fail in a "short" mode?

I am thinking its likely the Coil or ICM since I replaced the distributor, but that would only be shotgunning the problem.

If all else fails I may have to rig up something to feed power individually to one of the circuits at a time so I can tell which one is blowing, but thats hard to do without all the mating connectors.

Appreciate any help on this one.

Some time with a multimeter & a good wiring diagram (your FSM) should tell you if you have a dead/intermittent shorts somewhere in one of those circuits as far as the wiring goes.

The coil & ICM can be tested (I think it's posted in the Tech Article section). Not sure what multimeter testing can be done on a CKP as it's been awhile... The fuel injectors should all ohm out at near the same resistance.

Of all of the items listed, the coil & ICM are probably the most common component failures. As for wiring failures though, the wiring at the CKP sensor is something that has caused this problem in my experience and is often overlooked.

Thanks! appreciate the info.

Found the Coil and ICM troubleshooting link and copied it off in case I needed it.

Looked at the car again tonight after getting a bunch of fuses from the auto store :icon_wink: The fuse would blow now every time I turned the ignition on...great news, no more intermittent problem. Unplugged the Coil and ICM, fuse still blew, unplugged the Fuel Injectors, still blew. unplugged C4 from the VCM, still blew. Unplugged the CKP sensor, still blew. There goes all the easy stuff, now I know its in the wiring. So figuring the most likely place for the wiring to be bad is where the cable breaks away from the harness to connect to the CKP sensor, I moved it away from everything and separated the wires. Fuse DIDN'T blow anymore. So, looks like the short is near the CKP sensor wiring. Since it was dark and I didn't want to get under the car and pull the skid plate tonight, at least I think I have the problem area isolated. Not sure when I'll get back to it, but I'll post here if I get it resolved.

Bill

Fixed. Found that the wire loom about foot from the CKP sensor had slipped over to the exhaust manifold; melted thru the loom and the pink wire insulation. Yea! Just put about 10 miles on it and it seems to be running fine.