C3 random shutoff

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Apr 19, 2020 | 12:21 PM

Mogwai 1977

Thread Starter

3rd Gear

Joined: Apr 2020

Posts: 3

Likes: 1

C3 random shutoff

Hello all! I have a 1977 corvette that I purchased a couple of years ago. Car runs great unfortunately since I bought it the car has been plagued by random shut offs. I recently put a Fitech EFI on it and it still does the same thing. Strangest part, is that there’s no consistency in when it happens. It can happen when it’s hot, cold, or may not happen at all. I can drive it for an hour and it not happen, or I can pull it out run for 15 mins then just quit. I turn the key off, and it fires right back up. Any thoughts or suggestions on where to start diagnosing this issue. I’m pretty certain it’s ignition related. could be ICM, Coil, wiring? Would appreciate any thoughts you guys may have.

Apr 19, 2020 | 02:11 PM

sullyman56

Drifting

Joined: Nov 2013

Posts: 1,546

Likes: 281

From: Scottsdale Arizona

Failing ignition module?

Apr 19, 2020 | 05:39 PM

drwet

Melting Slicks

Joined: Dec 2009

Posts: 3,229

Likes: 656

From: Thunder Bay

Quote:

Originally Posted by sullyman56

Failing ignition module?

Very common problem on early HEI's. IIRC GM solved the problem with the addition of conductive grease under the module for heat transmission to allow the module to cool. Regardless, I would bet the family ranch replacing your ignition module will solve your problem. They're cheap. Try it. Good luck.

Apr 19, 2020 | 05:45 PM

Haggisbash

Melting Slicks

Joined: Oct 2012

Posts: 2,156

Likes: 273

From: Dunedin NZ.

Key switch contacts worn?

Apr 21, 2020 | 11:59 AM

Mogwai 1977

Thread Starter

3rd Gear

Joined: Apr 2020

Posts: 3

Likes: 1

Thanks!

Ordered a new ICM, should be in tomorrow and will give that a try. Cheap fix if it works. Thank you all for the help and welcome.

Apr 21, 2020 | 12:16 PM

jackson

Le Mans Master

Joined: Sep 2001

Posts: 7,739

Likes: 630

From: Unreconstructed, South Carolina

Use some GOOD thermal transfer paste ... something better that just any ol' dielectric grease

Amazon

Apr 21, 2020 | 12:34 PM

Big2Bird

Le Mans Master

Joined: Dec 2006

Posts: 8,837

Likes: 1,028

HEI module
Fuel tank filter sock
Ignition switch worn/out of adjustment
Loose wire connector
It should be one of these for 98%

Apr 25, 2020 | 04:29 PM

Mogwai 1977

Thread Starter

3rd Gear

Joined: Apr 2020

Posts: 3

Likes: 1

Icm

Replaced the ignition control module. I have driven it everyday for the past 4 days including about a 100 mile round trip this morning. Not a single shutoff. Thanks for the help all, fingers crossed it stays running!