Technical HEI No Spark

My 52 Chevy with a 350 and 700R4 quits running when it gets hot. I have replaced the module and coil (one at a time) and it still acts the same. It has fuel at the carb when it quits and will start and run if it cools for 45 minutes or so. It also has power at the distributor when it quits. Any ideas?

 

Pick up coil ?

 

Is your power to the HEI a full 12 volts dedicated feed? If it's less than 12 volts it will shut it down.

 

If your 12 volts passes thru the fuse block bypass it with a direct feed and see if it cures it.

 

A 10 gauge wire to feed 12 volts. Determine that the ground to the coil is good. This would include the contact that is under one of the screws that hold the coil in the cap.

 

Alot of times its the internals....check, clean, dielectric grease, yada yada...otherwise they are pretty reliable

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Look at the bottom side of your rotor

 

A little dab of dielectric grease on the terminals is OK. But if you're talking about what goes on the underside of the module you'll want to use thermal paste. It's a completely different compound that's made to promote heat transfer away from the module. Dielectric grease is intended to seal electrical terminals and connectors from moisture and to prevent corrosion.

 

How much power at the distributor when it quits?

HEI needs full 12 volts for starting and full battery/alternator output when running from a 10 to 12 gauge wire direct off the key switch. The key switch needs power right off the battery.

Replace module with good used GM unit, add thermo grease to back side to transfer heat away, clean the coil ground in the cap, and check the two small green and yellow wires coming off the pick up deep inside the distributor. The pick up unit rotates with the vacuum advance, so the wires are moving all the time and do break every now and then.

Hot wire the distributor right off the battery next time it dies and see if it will start.

 

Check the coil for a loose wire. HRP

 

I had the same problem.... and have read on other boards that HEI modules DO simply quit when they get hot. I got an MSD "Heat" electronic replacement module, and the problem went away. Sooooooo.....

 

The modules will suddenly quit, for no reason. Never.said dielectric grease under module. Module comes w a special sealant usually

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Correct terminal end on the wire to connect to the Hei? I had a hell of a time with one that had a slide connector on the wire rather then the HEI connector. It would invariably not get good contact after about 20 minutes of driving and usually at 3 am in a rain storm.
I've got the pages out of a bulletin NAPA put out 30 + years ago on troubleshooting HEI distributors on my photobucket . There are eight pages in the booklet and it bailed me out a number of times troubleshooting these things and even saved a buddy a tow job on a road trip in his motorhome as he had a copy along that I gave him. http://s173.photobucket.com/user/mr48chev/library/Napa HEI service info bulletin?sort=3&page=1

 

Hey Mr 48.... as usual, photobucket continues to screw everybody... I have an ad blocker on my 'puter, and when I click your link, pissbucket says "you have an ad blocker and we ain't gonna let you see anything on here unless you turn off your ad blocker...".... assjacks.....

SmugMug is a much better AD FREE web photo hosting site.. that's what I use.. fully configurable.. etc., etc., ....

 

I've got a smug mug account but haven't transferred them there as no one has complained before.

 

Hopefully in order

 

That should be all eight of them.

 

Nearly on entire page and no one told the OP to put in points?

 

My first thought was HEI module
Second thought pickup coil
It tells HEI when to fire.

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Check your rotor on the bottom for a burn hole and killing your spark on the dist shaft.

 

Pull the dist. Replace the pickup coil
You already did the coil and module
Tinkirk/Terry


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I have to say I have helped many a stranded rodder because of a burnt up rotor on HEI . That may not be your issue but just replace it with a quality part now or later on the rotor will be your issue when you really don't want it to be .

 

I have run a bunch of HEI distributors yes if the module heats up it will shutdown and start after cool down Also they will run down to about 10 volts, anything less than 10 volts they will shutdown. I had one unit that would shut down when warm randomly.Turned out after a lot of troubleshooting it was the pick up coil, seemed to be when the unit got warm/hot one of the wires would move slightly,,it had a broken wire and only showed up when the wired moved ever so slightly,found it by moving the wire and checking with a meter it would go Open,,Replaced the pickup and never had issues again

 

Experienced the broken wire before. Would work intermittently, but found it and fixed it/ Broken in the connector.

 

Thanks for all the comments. A new pickup coil seems to have fixed it. The Eichlin bulletin is also very helpful.

 

great you found it, I was going to say I have also had a broken wire in the coil.

 

The ground system of HEI's is one of the most common causes of an erratic performing distributor.