I replaced the distributor seal, which was leaking enough oil to have an occasional drip off the transmission casing.

You can see by the pic that the (still original) ignition wires preclude much rotation error on distributor re-installation.
Regardless, I marked the distributor location to ensure the orientation was correct.

After reassemby, the engine wouldn't start. So, I thought, what did I do???
My test light showed no spark from the coil, so I tried my new spare. Nothing.
Next I tried my spare ICM, and it started right up. Hmmm... too coincidental...
I noticed the old ICM spade lugs were corroded, so I sanded the corrosion off, applied dielectric grease and reinstalled the old ICM.
Bingo! Fired right up.

Even though I didn't touch the connector, moving the wires that attach to the spade lugs to ensure they were going to be inside the cap must have disturbed the connection.
So then I also put the old coil back on. Now I have new spares that have been tested & verified as good.

I had a spare ICM & coil due to a couple of warm engine no-starts 2 years ago. The following day, the engine would start.
After monkeying with the coil and ICM, the engine started & has since.
Now, I'm suspicious that the spade lug connection was the problem then too.

Since the distributor typically has corrosion issues under the cap, maybe rusty ICM lugs are the cause of some ICM replacements.
Next time you fault the ICM, have a look at the spade lugs. If they're rusty, try cleaning them and see if that fixes the no-start.
It might be enough to unplug and reconnect the connector a couple of times to restore a connection. Handy if you're out somewhere...

Anyone else have this experience?

Similar, yes. On mine the plastic clip that secures the two wires from the pickup coil to the module had cracked and fallen off years earlier and the two wires were just attached press-fit style to the spades on the module. Hardly a durable system anymore. And to make it even more troublesome, the green and white wires were both faded and discolored to the point of being nearly indistinguishable from one another. A module change required careful study of which wire was which otherwise it was 50/50 they'd go back on correctly.

quote Originally posted by css9450: Similar, yes. On mine the plastic clip that secures the two wires from the pickup coil to the module had cracked and fallen off years earlier and the two wires were just attached press-fit style to the spades on the module. Hardly a durable system anymore. And to make it even more troublesome, the green and white wires were both faded and discolored to the point of being nearly indistinguishable from one another. A module change required careful study of which wire was which otherwise it was 50/50 they'd go back on correctly.

Good points! I had this issue also. Multiple ICM replacements in the 1st 18 months I had the car. The first one was on my way to the 25th Anniversary Reunion. In my case it was heat related. The engine quit after several hours of running with no issues. Each replacement was installed on the side of the road. Tractor-trailers whizzing by at 70 mph impaired my diagnostic skills. I noticed the connector on the module had electrical tape on it, but didn't think much of it. When I finally took the time to check it out at home in the garage, removing the electrical tape revealed a cracked terminal housing. I had a spare pickup coil so I removed the connector housing from the spare and installed it on the existing pickup coil wires. That saved me from having to remove the distributor. I installed new terminals since I did not want to cut and splice the old ones. No issues in the last 5 yrs.

I have a sneaking suspicion that much of the ICMs bad reputation comes from user error. Either people fail to pack the electrical connectors with dialectric grease, or they apply the heatsink grease incorrectly (or use the wrong grease), or they don't tighten the ICM mounting screws correctly (so the ICM is tilted). Once again, this is just my opinion.

quote Originally posted by Blacktree: ...pack the electrical connectors with dialectric grease

Living on the coast, I'm a great believer in the use of dielectric grease. Gotta keep the dampness (and therefore corrosion) out of the connections!

Good advice! Thanks David for taking the time to point it out! I'll keep that in mind when I have to deal with that.

Out of curious, where did you make your mark for the distributor?

quote Originally posted by Fiero Vice:Out of curious, where did you make your mark for the distributor?

After I removed the clamp, I marked the distributor housing and engine block in the area where the clamp had been.

Just pointer, use only the GM AC Delco ICM. Plus use the di-electric grease. You need that.

Plus, every time you change the ICM, buy the 2 new GM factory screws. There not expensive. (10-15 dollars)
Old rusted screws can cause problems. They are the grounding point of the module.

A clean / maintained ignition system should last a long time. New GM parts are still available to re-furbish the system.
A daily driven fiero should have the cap & rotor replaced every year. 95% of owners don't do that. They wait an say, "I'll
replace that next year".

Many say / wait until their stranded and wonder why they should of done it before. Its simple maintenance.

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.

quote Originally posted by fierogt28: Just pointer, use only the GM AC Delco ICM. Plus use the di-electric grease. You need that.

And just to be clear, in case there's any confusion whatsoever with anyone reading this... dielectric grease is not used between the ICM and the base of the distributor. Heat sink compound/thermal paste is what is used there.

[This message has been edited by Patrick (edited 08-01-2016).]

quote Originally posted by Blacktree: I have a sneaking suspicion that much of the ICMs bad reputation comes from user error. Either people fail to pack the electrical connectors with dialectric grease, or they apply the heatsink grease incorrectly (or use the wrong grease), or they don't tighten the ICM mounting screws correctly (so the ICM is tilted). Once again, this is just my opinion.

Far more common that many think... Failed ICM is very often a Symptom, Not the main problem IE the Root Cause.

loose/rusting screws are a problem.
Bad main coil, even just poor mounting of it can fry the ICM.
See my Cave, HE Ignition

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

quote Originally posted by Patrick: And just to be clear, in case there's any confusion whatsoever with anyone reading this... dielectric grease is not used between the ICM and the base of the distributor. Heat sink compound/thermal paste is what is used there.

Patrick, thanks for pointing this out. Normally when you buy a new ICM there is heat-sink with it. Its in the box.
Yes, its more paste than grease.

------------------
fierogt28

88 GT, Loaded, 5-speed.
88 GT, 5-speed. Beechwood interior, All original.