Random HEI shut off

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Cudakid2967

Cudakid2967

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Have a bit of an odd extremely intermittent problem going. Have a LA 318 with a GMC style pro-form hei distributor. Every once in awhile the car will just turn off like key was turned off. No stumble or rough running, just an instant ignition cut. It'll instantly fire right back up no issues and won't do it again for a week and then randomly do it again. Always at just above idle as I'm like pulling through a parking lot or yesterday as was pulling away from a light. Any ideas on what should look around for to see why it's doing it? Would like to be able to fix it because becoming slightly annoying especially when decides to do it as you're pulling away from a stop light lol.
 
Do a voltage drop test from the ignition switch through the fire wall connector to the distributor. Ign 1&2 should be tied together at the ignition switch for HEI. Resistance builds heat and expands contacts. Cool down and connection returns. The module could also be going bad or loose screws not allowing good heat sink.
 
Try changing the HEI Module, they are known to go bad even the new ones.

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And you need a good working E-coil to work with HEI properly, running on straight 12 volts and no ballast resistor .

The old style round coils overheat and just don't cut it with HEI.

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My vote is HEI module- make sure lots of special grease on mounting side. Make sure it is a better quality unit and not a chyna special.
 
HOT WIRE direct to the HEI and see if it quits. If not it is the car harness and not the ignition. If it is the HEI quitting, you basically have three choices...the module, the pickup, or the coil.

I built myself an "emergency" HEI which also helps me to fire up old engines, occasionally, AND TO troubleshoot, as I can clip it in and eliminate components

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I can
...Hot wire it in, which eliminates the car harness AND everything except the distributor. You can put clip leads into the pickup connector and clip it to the HEI pickup coil. You can "de wire" the coil and hook the emergency module to the present coil to test it

Green wire is ground, Yellow is power connection. No ballast
 
Should add the car has been completely rewired with an American Autowire update kit so isn't any old wiring or ballist resistor or any of that stuff
 
Is the vac adv hooked up? If yes, I suspect a broken pick up wire. When the VA operates, it moves the p/up coil which flexes the wires. After enough miles, the wires will break from continuous flexing. Since this only happens just above idle, & is consistent, it rules out most other things.

You can measure the p/up coil, should be 200-1200 ohms. Flex the wires will doing it to see if it goes open cct.
 
Cudakid2967 said:
Should add the car has been completely rewired with an American Autowire update kit so isn't any old wiring or ballist resistor or any of that stuff
Click to expand...
Not even relevant. There can ALWAYS be a problem with a connector, terminal, or key switch. You need to test the system
 
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