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Discussion Starter · #1 ·
I added an HEI to a '71 Chevelle, now the engine won't turn off when they key is shut off.

I need some specific help here, I already got some advice to splice in a diode in the #4 wire on the regulator, which I did, but that didn't cure anything. I put the diode in with the stripe side away from the regulator (towards the alternator). Any other ideas?

Thanks.
 

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Where did you tap the power in on the HEI? If it is plugged into a wire or a spot on teh fuse panel that is always hot, teh key won't shut it down. It has to be tied in with the ignition. I have made the same mistake before.
 

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Discussion Starter · #3 ·
It's plugged into the ignition terminal in the fuse box. It doesn't go dead because it's being fed from the alternator.
 

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What happens if you open up the brown regulator lead as a temporary test? That’s the wire from the regulator back to the idiot light. Does the car shut off? That should prove/disprove the alternator being the problem. Haven’t heard that there’s a run on problem with a GM HEI but hardly know everything.
 

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Discussion Starter · #5 ·
Well, I unplugged the brown wire, which is "#4" on the regulator. It won't shut off.

Here's the problem- the "ign" terminal I'm using is hot when the key is in the run and start position. That terminal is dead with the key off. However, if the engine is running, when the key is off the terminal is still hot.

I've had quite a few people, including MSD and Jacobs, tell me this is common when adding an HEI or CD-type ignition to pre-'73 GM cars, as those ignitions require little juice to keep running, so when there's feedback through the fuse box, it's enough to keep an already running engine running.

Out of 14 cars converted to HEI, this is my first one with something like this, so I'm stumped.
 

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Let me think about it a little. Maybe someone else will see it. Well, it’s not the alternator doing it. Not sure what the techs at MSD were talking about referring to a feedback loop through the fuse block. The MSD run-on is caused by voltage on the brown wire, through the idiot light, to the pink wire that comes off the ignition.
Anyway: First thought. Is the idiot light working normally when the brown wire is hooked up?
 

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As stated above, you are certainly getting some kind of back feed to your HEI. However, I am sure it is not a basic feature of your charging system as I am using an HEI powered by a relay that gets its signal from the original resistor wire and it shuts off just fine. That relay requires close to nothing for current to keep it turned on. There are folks that have used the identical system as mine and did have shut off problems until they got a new (and good) voltage regulator. Just for fun, try measuring the voltage on your old resistor wire while it is in the run-on mode. IF there is no voltage there, then you have another mystery.
 

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Good thought about the resistor wire. If that’s not tied to anything, there shouldn’t be any voltage there when the key is off. If there is, have a couple of ideas on how to narrow it down. Not great ideas but something.
 

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Discussion Starter · #9 ·
Thanks for all the help. I finally figured it out.

I've only had this car for a few days. The alternator was hooked up using the wrong wiring. I have two other '72's that I compared it to, and some goofball had the wrong wires hooked up. Even so, it charged just fine.

But, it also powered the "dead" terminals when it wasn't suppose to.

Have a great week, mine is getting better.
 
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