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eating ignition control modules

B

BowtieBlazer

Diesel Powered
Joined
Jul 15, 2001
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Location
Baton Rouge, Louisiana
88 355TBI

One morning this week I got in my truck started it drove about a tenth of a mile to the gas station shut the truck off went inside came back out bumped the truck over and it sounded like it was going to crank so i let off immediately and then i heard a pop from the fuse box. IGN fuse was blown I put a new fuse in turned the key to ign on not even the start position and each time i would it would blow the ign fuse. I then found that two of the three wires going to my 02 sensor were touching the drivers side header. Separated those two and then it stopped blowing that fuse but would not start despite the starter rolling the motor over. I bought new wires to replace the two burnt ones and splice them in. No change and now i notice no fuel. I decided it was the ign cont. mod and walked down to napa and paid the $73 they wanted for a new one off to work i go....

fast forward to that afternoon, i hook to a 8x12 enclosed trailer to drag home for a friend of mine and hit the road. 60 miles into the trip on the interstate doing 70 the service engine soon like comes on momentarily the truck sputters then the light disappears and the truck resumes running fine. 20 miles later i get onto some broken concrete sections on the interstate hit a good bump that jarred the cab and the light comes on then the truck engine dies i shift to Neutral and crank with no luck of restart, get towed off the interstate and to a friends house decide it the module again goto advanced auto get a new ign control module replace it and the remote starter solenoid i mounted on my firewall to help with the heat soak problem i was having incase the contacts in that were getting crusty and opening the circuit. drive 70miles home uneventfully and another 120 since then.

I am looking for diagnosis to possible causes the battery is mounted in a tray and clamped down the terminals are tight. I am replacing the battery cables just incase. eitherway if the hwy causes this what happens when i get offroad. By the way if your truck will not allow the injectors to fire and your service engine soon light doesnt come on before you start the truck its probably the ignition control module
 
Did you put the di-electric grease on the bottom side of the control module? If you didn't use di-electric grease on your module you will fry it. Have you replaced the pickup coil? Pickup coils can cause some wierd stuff to happen if they are going bad.

Harley
 
P.S. Go to checker to get a module. I think there Neihoff modules are like $40 instead of $73.

Harley
 
Hossbaby50 said:
Did you put the di-electric grease on the bottom side of the control module? If you didn't use di-electric grease on your module you will fry it. Have you replaced the pickup coil? Pickup coils can cause some wierd stuff to happen if they are going bad.

Harley
Click to expand...

new coil and yes i did use the di-electric grease...
 
Do a check on your charging syatem to se what voltage you are running. Don't trust the truck gauge.
Also, look for any wires that are exposed. I wire exposed, that comes into contact with a ground, can cause the same thing.
 
BowtieBlazer said:
new coil and yes i did use the di-electric grease...
Click to expand...

Hoss isn't talking about the ignition coil, there is what's called a pick-up coil located inside the distributor. You have to pull the distributor out and take it completely apart to change the pick-up coil.
 
I thought of one more very important thing. I don't care what your grounds look like right now, run a new ground wire from engine to frame, and engine to body. A while back, doing that fixed that exact problem on a buddies Burb. I think he even ran another single wire to tie them all together "just in case".

One more thing. Take the cap off and pay close attentin to the guts of the dizzy. I had one that the magnets had cracked on and it caused all kinds of problems. I had to take some time looking, to see it.
 
Leper said:
I thought of one more very important thing. I don't care what your grounds look like right now, run a new ground wire from engine to frame, and engine to body. A while back, doing that fixed that exact problem on a buddies Burb. I think he even ran another single wire to tie them all together "just in case".

One more thing. Take the cap off and pay close attentin to the guts of the dizzy. I had one that the magnets had cracked on and it caused all kinds of problems. I had to take some time looking, to see it.
Click to expand...

I suspect grounds could be a problem that is one thing i have not thought much about but have noticed the small straps that are there...I will be r&r them soon.
 
There is not a thing wrong with GM's grounding system.

I'm not saying that YOU don't have a wiring problem related to ground, because it is a pretty common problem in other areas of the trucks, just that as designed, GM's grounding is over-engineered. You don't need to increase the amount or size of grounds just because. If the grounds aren't adequate, something is wrong that should probably be fixed, not just worked around.

Of course these are my opinions, I've only wired up my one truck. But I know for a fact, when wired properly, these things work, or they wouldn't have left the factory.
 
Leper said:
I thought of one more very important thing. I don't care what your grounds look like right now, run a new ground wire from engine to frame, and engine to body. A while back, doing that fixed that exact problem on a buddies Burb. I think he even ran another single wire to tie them all together "just in case".

One more thing. Take the cap off and pay close attentin to the guts of the dizzy. I had one that the magnets had cracked on and it caused all kinds of problems. I had to take some time looking, to see it.
Click to expand...

Ya, if the reluctor ring is cracked it will do all kinds of funky stuff. It will run one minute then not the next. It will crank and crank and crank and nothing. 10 minutes later it will fire up like nothing was ever wrong. I had that happen once too.

The reluctor ring is the metal ring with triangle points on it on top of the pickup coil underneith the dist cap.

Harley
 
I added an additional ground wire from the motor to the frame and replaced the battery to frame ground wire.

I also found that one of the coil braket mounting bolts had rattled loose and was no existant so i replaced that. So far a couple hundred miles with no service engine soon light. I'm hopeful.
 
its back tonight i had the reoccuring problem numerous times on roads it normally had been doing fine. I thought maybe it could be in the column but the tilt steering column is pretty tight and when i shake it while the truck is running i get no idiot light. Tommorrow I will check the distributor coil and other wiring.
 
okay here we go again:
yesterday i pull the blazer under my driveway and start looking for the new culprit. checked for loose wires nothing disconnect the battery and pull the distributor cap check the wires to the ign module everything seems fine get it all back together and i suddenly have no interior lights and no service engine soon light before cranking and of course no fuel. run to the auto parts store get my ign. control mod. swapped out and buy a pickup coil as well.

today change the pickup coil and ign. cont. mod. and get it all back together i have the service engine soon light now and once again have interior lights crank but no fuel... i check ohms on the old and new pickup coils and both test out fine. I am baffled on the ign control mod issue. I will check the ignition coil again tomorrow....frickin frackin .....i can hear the pump and relay open when bipassed the pump will run from the priming wire. I need to verify no spark tomorrow am as well.

i hand cranked the truck to TDC to verify that I had restabbed the dizzy correctly and that was all fine...

running out of parts and pieces to replace :mad:
 
Leper said:
I thought of one more very important thing. I don't care what your grounds look like right now, run a new ground wire from engine to frame, and engine to body. A while back, doing that fixed that exact problem on a buddies Burb. I think he even ran another single wire to tie them all together "just in case".

One more thing. Take the cap off and pay close attentin to the guts of the dizzy. I had one that the magnets had cracked on and it caused all kinds of problems. I had to take some time looking, to see it.
Click to expand...
looks like it must have be the reluctor magnets on top of the coil i had another dizzy sitting around and swapped magnets and its got spark and fuel again with the original pickup coil
 
as an update I think the original tripping factor was the field wire going to the alternator. Although the wire was not frayed it appears to have been smashed flat at some point in time. I have yet to get stranded since i discovered this, I'm sure its what was eating the ignition control modules with hard bumps it would arc continuity and flicker check engine light. Sometimes this was enough to shock the ICM
 
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