Ignition Control Module

[nissanracer29]

I have a 1976 Jeep J10 with the prestolite ignition. I have gone through and check what I could and it either could be a bad ignition control module or possible the pickup in the distributor. It will run for about 15 minutes or so and then shut off. I have a new coil and control module however I have tried 3 modules with none of them working. When I connect the old one it will fire up and run until it gets too hot and shut off. Is there a reason the new modules dont work? I know I can swap out the ignition system to something better but am just curious why these new modules dont work. Thanks in advance.

[tgreese]

I have a 1976 Jeep J10 with the prestolite ignition. I have gone through and check what I could and it either could be a bad ignition control module or possible the pickup in the distributor. It will run for about 15 minutes or so and then shut off. I have a new coil and control module however I have tried 3 modules with none of them working. When I connect the old one it will fire up and run until it gets too hot and shut off. Is there a reason the new modules dont work? I know I can swap out the ignition system to something better but am just curious why these new modules dont work. Thanks in advance.

First post. Welcome from Boston.

I don't think there's much experimenting done with the Prestolite modules. There is a single big transistor in them that turns on and off to switch the coil. Possibly the aftermarket suppliers are under-specifying that transistor to lower costs and it's overheating. Or maybe your coil has such a low resistance that the module is sinking too much current. Or maybe the module circuit is poorly designed, and cannot limit current the way the original modules could. Possibly you could add a ballast resistor between the ignition switch and the coil, though the original implementation did not need one.

The Prestolite BID stuff (breakerless inductive discharge) was used by Jeep from 1975 through 1977. My '77 still has its original ignition and is running an Eichlin module from Napa that came with the truck. The BID is widely considered a colossal failure. This intermittent operation that you describe was a common feature.

The usual advice is to abandon this ignition system and go to one of the other Jeep ignitions, or go with an aftermarket GM HEI clone. I'm not a fan of the HEI, but there are many here that like them. Jeep used a Delco points distributor prior to 1975, and a Ford Duraspark magnetic distributor and module from '78 on. Both are excellent units. There's also a billet distributor from MSD (?)

You have lots of options for a different ignition system, but near zero options with the BID system. Its operating principle is unique and not compatible with any other ignition systems. Clean the plug contacts (module and pickup) with quality contact cleaner and apply a bit of dielectric grease for corrosion resistance, run a dedicated ground wire from the module to the coil bracket, replace the parts with whatever aftermarket replacements you can find.

[backroadin']

Another good option is a Pertronix unit - it's a drop-in module for the distributor. I'm not sure if they make one for the prestolite dizzy, but they do for the ealier Delco one like I have. It's a simple two wire setup and is essentially an electronic ignition setup like an HEI. Other companies make drop in modules like it too. When I did mine, I went with a new coil too. No issues in 15 years. I went with a GM 10si one wire alternator as well and really simplified my wiring.
If this truck is something you plan on keeping for awhile, I would definetely suggest to convert the ignition over to something else - for ease of finding parts and also reliability. Like tgreese said, there's lots of options - HEI, pertronix, the later Ford Duraspark conversion, even back to points if you prefer them! Lots of info on this site (and other older jeep sites) about all these options. They are all pretty straight foward swaps. I believe the earlier and later distributors will drop right into your motor, the GM HEI dizzy should too, but you'll need to swap the gear.
Good luck with the jeep and welcome to the forum!!

[fulsizjeep]

Your problem sounds familiar. I had it plague my first Prestolite for a few weeks until I dug inside the distributor and found the insulation on the pickup wires was falling apart and they were shorting out to shut everything down... I have HEI nowadays.

[Heep-J4000]

The pertronix is a good option like backroadin suggested!
Had one on my 360 and wished I did know this year's earlier.
It never gave me trouble after installing and it runned much much better and never needed a tune up anymore!

[tgreese]

No Pertronix conversion module for the BID distributor that I can find. You could fall back to the Delco distributor and convert to Pertronix, though their product for Delco 8cyl distributors does not specifically list Jeep as an application. https://pertronixbrands.com/products...31797176664100

Should work - you'd need a replacement Delco distributor from somewhere, then fit it with the Pertronix conversion. Currently RockAuto only lists send and return rebuilt for this distributor; this means they have no cores.

https://www.rockauto.com/en/catalog/jeep,1973,wagoneer,5.9l+360cid+v8,1184037,ignition,distributor,7108

If you want a Delco, post up in the WTB section here, and someone might have a used one. The Delco with points could also be used to trigger a MSD capacitor-discharge module, providing very long points life and a much hotter spark.

OTOH, you could buy a complete Pertronix distributor from Pertronix for about $300.

The Duraspark distributor is more available than the Delco

https://www.rockauto.com/en/catalog/jeep,1978,wagoneer,6.6l+401cid+v8,1309924,ignition,distributor,7108

This is a magnetic distributor that can trigger a variety of different modules, including MSD, GM HEI, the Duraspark module, among several. This would require more electrical savvy to install, but it's a flexible choice.

The HEI distributor has its issues, but may be your best option if you can't handle connecting up the Duraspark and can't source a Delco.