jpkemp

Have a 1978 Corvette with low mileage. Every 1-1 1/2 years I have to replace the Ignition Module because the car cranks but will not start(no spark?). First 9 months with a new IM, car starts no problem. After 9 months go by, it takes longer to start and eventually wont start - can always tell when the IM is going bad(takes longer and longer to start). Once I get it started, its starts when warm with no problem. After replacing the IM, car starts no problem.
So my question is - why does this module keep going bad? I have replaced the guts in the distributor, ground wire is good - what gives?
Its not a hard job/repair to do, its not expensive, just don't know why..
Thanks

71VetteLover

I assume you're referring to the ignition module inside the HEI? If so I suggest buying a Standard Module (good) or an MSD (better) because they're quality modules and they DO cost more.

'75

Be sure to use the heat sink compound under the new module, it helps to transfer heat from the module to the distributor housing. Heat kills these things.

jpkemp

Yes, the ignition control module - I usually buy the AC Delco replacement..Just don't know why they keep going bad,,

jpkemp

Usually use all of compound included with the module,,,Its just mind boggling why I have to keep replacing them every so often

tracdogg2

Make sure the coil ground strap is inside the cap. It goes in the center port of the 3- wire terminal.
Make sure your plug wires are good, A bad wire will zap the module.
Mike

jpkemp

As usual, every year the ignition module has to be replaced in order to start the car. Just replaced the IM last Wednesday, car fired right up. Went to start today(Saturday), would not fire up. Battery has a full charge, starter is good, not sure why this car will not start. Could it be a bad IM even though it started fine on first crank on Wednesday?..Any idea why this keeps occurring on a yearly basis or why this car won’t start after replacing IM five days ago. Plug wires are good, cap/ rotor seem to be fine. Any assistance is appreciated.

CA-Legal-Vette

A bit of a long shot, but what plugs and gap are you running?

interpon

What brand are you buying? Try some ebay usa made nos

jpkemp

AC Delco R45TS gapped to .045, just replaced the plugs recently...Also replaced the Spark plug wires...

jpkemp

AC Delco original replacement...bought off of Amazon. As stated, these ignition module(s) are usually good for a year. When replaced car starts on 1st crank then progressively starts on 2nd crank about 6 months later.

Bikespace

Is your alternator spiking and killing the module? If the problem isn't heat, perhaps it is electrical.

fake

Your battery charger is most likely spike it .Try plugging charger into receptacle with built in surge! Also any wireing under rotor make sure under side is not grounding to Distrubutor base which is metal Alot of heat will destroy module also so try a different heat sink manufacture under module. Good Luck!

bmotojoe

Make sure you are getting a good ground path to the module mounting screws from the distributor hold down clamp.

interpon

i would look for USA made and try that.
if this one...

sort reviews always from most recent not most helpful...and look at questions and answers..
AC Delco jumped the shark a long time ago on part quality..
reviews full of no markings, doesn’t last...etc...

anything nos USA even standard products would be worth a shot and cheaper...imo

example

https://www.ebay.com/itm/1-NOS-Delco...AAAOSw0sxgOXCm

CA-Legal-Vette

Well that isn’t it.

Mrvettenick

Just curious....what kind of ignition coil are you running, and have you measured the primary resistance? A coil that's out of spec will take out modules.

jpkemp

After I replaced the module on Wednesday, I did not place the car on the battery charger. I ordered another module yesterday, stock D1906 but I am going to use a different heat sink...

jpkemp

Last replaced cap, rotor, and coil early last year - Echlin premium...
Car started no issues for a year, but the last 6 months required multiple cranks to get motor started.
Have not measured the resistance but this has been an ongoing problem for many years....
Module would last for a year and crap out..This is the first time it has only lasted for 5 days...
I will install another module this week with different heat compound...

carriljc

It's not an ECM. It's an ignition module. Using the correct terms is important in communication. Using the search function works a lot better if you use the right word.