repeaditely blowing ignition modules inside distributor

i have a 1986 nissan pulsar, no ECU, just basic E16 engine. I've gone through 4 ignition modules inside the distributor. once the first one blew, the next one lasted 5 minutes. I had forgotten to put the di- electric grease on the back. The next one i put in lasted 3 weeks, up until yesterday when it blew again. The third one i put in, i gracoulsy lathered the dielectric grease on the back of it, and it lasted 15 seconds.

Note: these are used modules i'm putting in, because new ones are 250$ a pop. Any ideas?

Reply to
mechjames
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I think ground issues or ground theft issues when I hear something like that.

I have seen quite a few distributors lose their physical ground via the hold down foot and have to steal a ground through the wiring which fries things.

A multimeter can tell you by seeing if you have a voltage drop from the distributor case to the battery if running or in ohms for a resistance from the distributor case to the battery negative. It should be pretty much 0 ohms.

Mike

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Reply to
Mike Romain

so do I need to put in a new module before i test this? doesn't it get a 12v connection when i turn the electric on on the key? or would it have to go through the module to the distributor first? because the two wires from the +'ve and -'ve sides of the coil run to the module.

Reply to
mechjames

I am talking a 'basic' physical case ground for the module with the feed physically through it's bolts to the distributor, it's foot, then the block, then the battery negative cable.

I know when this route is lacking on lots of modules, bad things happen....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Reply to
Mike Romain

so if the resistance is above 0 ohms, the distributor needs to be replaced? (i have 4 around here), or just clean and wirebrush the distributor foot?

Reply to
mechjames

Clean the foot.

Mike

Reply to
Mike Romain

and the foot is where it bolts down?

Reply to
mechjames

I would also check the resistance between the engine block/head and the battery negative post.

Reply to
Dyno

I would also try another coil.

Reply to
Steve Austin

the coil was changed 3 months ago.

i guess if the resistance is too much, i have to clean my grounds off.

what bugs me is the random times it takes to blow these things.

is it possible by putting too much dielectric grease on, that it looses its ability to disappate heat? is it only suppost to be a thin layer on there?

Reply to
mechjames

Just like doing a CPU in a computer. You want just enough to fill any air spaces there may be between the two surfaces.

Reply to
Noozer

damn that might have been what blew the last one so fast. i gobbed it on there.

ok i'm going to check the resistance thingy, clean all the grounds, and apply a tiny thin layer of grease.

Reply to
mechjames

Did you change the coil before you started blowing modules?

Reply to
Steve Austin

Yes, that, the bolt and the flat spot on the block need cleaning on some.

Too much dielectric grease on the module will not cause a failure, it is there to help draw heat away. Too little is the issue.

Mike

Reply to
Mike Romain

i put on a new coil back in the summertime, and drove it around for 3 months, and it ran just great! I decided to rebuild the engine during the past year and the probelm has only started since. the distributor foot corrosion might make sense since the timing might be in a different position than what it was set at before, and it is a bit corroded. i will find out today and get back to you.

It had run awesome for the past three weeks though.

Reply to
mechjames

I hope it's Thermal Transfer Grease/Compound you're putting on, and not dielectric grease as you state. The two are not the same!

Reply to
Ed.Toronto

no i've been using the permatex dielectric grease for spark plug boots. the guy at the auto parts store said it was the same.

resistance anywhere from the distributor case to batttery ground never goes above 1 ohm. there is this thing above the coil, looks like a resistor of some kind, and the wire is broken and just wrapped aruond the end of it. it runs to the distributor ground hookup, but when that bare wire touches the car frame, it has power because it arcs against it. i'm guessing that somehow that is related to my problem.

i'm going to try and find a wiring diagram

Reply to
mechjames

Not even close. If the module is heat-sinked through its base, you have to use the right stuff ("heat sink compound" may be the better name). I have no idea if the module in your car requires this or not, but if it does, you can't just use dielectric grease.

That's a capacitor I expect. I'm not sure if it serves anything in an electronic ignition system beyond keeping down RFI.

Reply to
Ed.Toronto

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