ICM Relocation
 

Previous post, I talked about possible ICM issue, resulting in:
1. Dying after extended idling - not being able to restart without waiting about 15 minutes.
2. Not able to restart after short shutdown (example, run into store for 5-10 minutes). Again, open hood and wait to cool down.

So, tried ICM touching head - ICM spaced off of head, ICM with heat transfer paste between every piece of bracket, blah, blah, blah.

Used IR camera to see just what's getting hot and just how hot.
When warmed up, running, 93 degree day.
Cylinder head (where coil/ICM mounts), ICM, it's heat sink AND the coil, ALL 200-210 degrees.
After shutdown, temps slowly climb, as might be expected.

With, what seemed to me to be "junk science" regarding the cylinder head being a necessary heat sink to remove heat from the "heat generating" ICM,
OR spacing the ICM from the head, I decided to just move it away from the engine.

Since I just installed a K&N CAI, these is a pretty good space available when the stock air cleaner lived (SS models have even more room)
I bought an oversized, finely finned heat sink from Amazon and an OEM PT757 connector from eBay.
This would have required splicing in about 12-16" of wire to reach the ICM's new location (and 8 solder joints w/heatshrink).
I searched for the "female" connector (ICM side) but was not able to find.

Having bought a Casper Electronics 109068 Cooling Fan Control Module and seeing how nice their connectors were (inline, male and female), I contacted them
and "Joseph" said he could build me a custom extension for my ICM harness.


Just mounted the ICM to the heat sink, and build a crude mounting bracket from scrap at my buddy's shop (used his Bridgeport to drill & tap 8-32 holes for the ICM and bracket.
You'll notice I have 2 ICMs mounted. The "old" one was bought in July 23 and is 2 months out of 1 year warranty.
(Alternator from Rock Auto bought 8/31/22 - died less than 10 days out of 2 year warranty!!)

Bottom line...
Today 90 degree afternoon.
Temp on "hot" (the one being used) ICM was 115 degrees. This right after pulling into driveway, redline 3rd gear pull offramp.
"Cold" (spare) ICM 111 degrees.
Cylinder head 188, coil 186!

Pics below.

https://cimg6.ibsrv.net/gimg/www.cam...4abf0203d.jpeg
https://cimg7.ibsrv.net/gimg/www.cam...5a49bc9b3.jpeg
https://cimg8.ibsrv.net/gimg/www.cam...c9070c6a6.jpeg




https://cimg6.ibsrv.net/gimg/www.cam...22b54b0b5.jpeg
Relocated to the path of air that was occupied by factory air cleaner (behind headlights).
https://cimg0.ibsrv.net/gimg/www.cam...4e856fe2c.jpeg
“Hot” ICM, only 114.4 degrees!
https://cimg1.ibsrv.net/gimg/www.cam...f119bbd65.jpeg
“Cold”, unused ICM, 111.1 degrees.
https://cimg7.ibsrv.net/gimg/www.cam...dc86db44b.jpeg
Cylinder head, ICM area, running.
https://cimg9.ibsrv.net/gimg/www.cam...e9a60e9a3.jpeg
MSD Coil, running
https://cimg0.ibsrv.net/gimg/www.cam...d13336867.jpeg
Cylinder head, 5 minutes after shutoff.
https://cimg6.ibsrv.net/gimg/www.cam...352858b26.jpeg

Re: ICM Relocation
 

That is a nice setup. Was looking to do the same, but trying this instead.
https://cimg4.ibsrv.net/gimg/www.cam...c08241571b.jpg
This is what i did. Should look at a bigger heatsink. Also thinking of installing a 12v computer fan to either run all the time when running, or hook up with the rad fan to come on when they do.

Re: ICM Relocation
 

My $.02 is a failing ICM can take out a coil and visa versa. Relocating both may be a better path to minimize heat exposure

With that said, in over 25 years and 150k mi, I have only had ICM fail once in its stock location. Nothing unusual over any other part lifespan for comparative time/mileage. YMMV

Re: ICM Relocation
 

I have also never had an ICM fail. When attaching the ICM to the heatsink, did you use a high quality thermal paste?

Re: ICM Relocation
 

Thanks for your input.
Yes, on the thermal paste - always used it - every time I monkey'd with the ICM.
After numerous warm stalls/warm no-starts (idling, in my driveway), I determined that the problem was my fuel pump. It didn't occur to me to even check this, as we installed a new AC Delco unit when the car was resurrected in 2023 (along with new fuel tank AND all those new sensors...).
The Usual Suspects (self-proclaimed Forum contributors - here and FB groups) were directing me toward Water Pump Temp Sender, Opti, IAC and other possible issues. ( I even bought 2 new water temp senders, as those were not replaced in 2023)
I connected an induction timing light and wedged it in my open door, while waiting for it to die. It never failed to flash (even when cranking). Finally, it just wouldn't re-start.
I was sure this was ignition/PCM/injector-related (as in flooding or no spark) as i swear I smelled strong fuel odor when this problem occurred.
Obviously, connecting a test fuel pressure gauge (and absence of fuel pump sounds) confirmed that i wasn't getting fuel.
Not wanting to "drop" the axle, I cut a hatch to install a "GM Delphi" fuel pump and it started immediately. I've since purchased a Racetronix LT1 kit w/Hotwire, to be installed when we wire in my AEM WideBand for future tuning.