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Car dies at random, seems like no spark.

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#22 ·
No, don't just arbitrarily change parts out.

The coil AND module can be checked on the parts store run tester, off the distributor, and run them on the machine for a while, let them get to operating temps.

Pickup is the round part under everything that has the 8 prongs, and two wires out of it, and the vacuum advance pin connected to it. Where to check is at the two wires from the pickup to the module, there should be a plastic connector with both wires in it. Disconnect it from the module, and use an ohm meter lead in each wire socket, and "wiggle" the connector, see if the ohm meter shows a wire disconnect, then connect, etc.

A note about magnetic pickups for the HEI's, they are rotationally specific, have a coil in them which is the two wire coil, a magnet, one way, right rotation, other way, left, and a holder. The coil is replaceable separately, but, if the outer ring of the unit isn't centered correctly, the tips hit the inner tips, and the pickup will be damaged. Pickups are available completely assembled and centered, new, for about a buck more than just the coil.

"I think I was combining your two points. If I follow you, the coil could be going bad which in turn will ruin the module. OR. The wires from the pick-up coil are breaking. This distributor only has two summers use on it, how likely is it the wires would be breaking with only that much use?"

YES, both are possible, and both can occur separately, or, in conjunction with each other. Yes, failure of even new parts is common especially at the pickup to module connector wire junctions. Coils are another thing alltogether, they can be 'new - defective' straight out of the box, and the reason to check them, and modules, BEFORE leaving the parts store when purchasing them new.
 
Discussion starter · #23 ·
dave ray said:
No, don't just arbitrarily change parts out.

The coil AND module can be checked on the parts store run tester, off the distributor, and run them on the machine for a while, let them get to operating temps.

I actually did have them checked, they both tested out fine. He even ran the module several times, it was warm when he gave it back. Can they come and go like that?

Pickup is the round part under everything that has the 8 prongs, and two wires out of it, and the vacuum advance pin connected to it. Where to check is at the two wires from the pickup to the module, there should be a plastic connector with both wires in it. Disconnect it from the module, and use an ohm meter lead in each wire socket, and "wiggle" the connector, see if the ohm meter shows a wire disconnect, then connect, etc.

Thanks, that helps a lot. If I follow though, to test it'm going to need to pull the dist. and take it apart to get the the pickup separate, right?

A note about magnetic pickups for the HEI's, they are rotationally specific, have a coil in them which is the two wire coil, a magnet, one way, right rotation, other way, left, and a holder. The coil is replaceable separately, but, if the outer ring of the unit isn't centered correctly, the tips hit the inner tips, and the pickup will be damaged. Pickups are available completely assembled and centered, new, for about a buck more than just the coil.

"I think I was combining your two points. If I follow you, the coil could be going bad which in turn will ruin the module. OR. The wires from the pick-up coil are breaking. This distributor only has two summers use on it, how likely is it the wires would be breaking with only that much use?"

YES, both are possible, and both can occur separately, or, in conjunction with each other. Yes, failure of even new parts is common especially at the pickup to module connector wire junctions. Coils are another thing alltogether, they can be 'new - defective' straight out of the box, and the reason to check them, and modules, BEFORE leaving the parts store when purchasing them new.
Click to expand...
I actually had the module that came with it fail almost immediately so I understand what you are talking about but woudn't have thought to have them check one before I walk out the door with it, good point.

Looks like I've got a few things to check out.

Thanks
 
#25 ·
Since the harness has been worked on here's what I'd do.....

If your local parts store has the HEI pigtail connectors, get another BATT connector and try this:
Connect one to a long piece of 12AWG wire and run it to the battery positive.
Just leave it hanging out of the way by the distributor.
Next time the car has the no start condition, unplug the BATT connector and plug your other one in that comes straight from the battery.
If it starts up, you've hopefully eliminated the dizzy as the culprit.
If it doesn't, you've hopefully eliminated the ignition power circuit.
Sometimes it helps just to get some stuff off your plate when troubleshooting.
 
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Discussion starter · #27 ·
Steiner, what about this? I checked the power at the dist with the key on, had 12 V, if I checked it while someone turned it over to see if it held 12 or dropped to 0 in the start position wouldn't that do the same thing?
 
Discussion starter · #28 ·
Update. I plugged the voltmeter into the power plug going into the dist. With the key on a constant 12 volts. Crank it over and it drops to 8. Is this normal? Is this enough for the coil and module to do their job?
 
#29 ·
Look, quit beating yourself up over this. People have gone into auto parts stores and had to go thru 5 brand new modules before finding a good one. They fail. Rapidly. The ones that don't are genuine GM AC Delco parts. Go to your local Chevy store and pick one up.

As it has been explained before, you will see a voltage drop while crankng. There are ways to wire it to get more than 12 volts to it at all time. Worry about that after you replace the module and get your car running.

You are now entering the stage of listening to too much advice and worrying about things that have only a remote chance of being the problem. HEIs are a good design distributor. MSD stuff aint the greatest when it comes to reliability anymore. Get it running and when you have some time, go get a graveyard GM HEI and follow any of a dozen available instructions on how to rebuild it. Put it in engine when you get some spare time and aren't feeling frazzled and under the gun.
 
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Discussion starter · #30 ·
Honestly not feeling that frazzled, just trying to learn as I go. I didn't know there was a voltage drop during cranking so that was something new and just reinforced that yes, it's in the distributor, so that helped. At this point it sounds like an easy check to test the pick up coil so I'm going to do that. I also think I'll pull the module and have them test it again.
Thanks for your time and help.
 
Discussion starter · #31 ·
Update. Had the module and coil tested again, both tested ok although the coil was pushing the limits. Whatever it measures the cut off is .8, they consider it failed at .9, mine fluctuated between .6 and .7

Put them back in, it started. I did discover one of the three metal female clips in the plastic clip that plugs into the dist. Cap from the dist can push out. I would think once they were pushed together they would hold tight enough but maybe it's coming loose. Next time it dies I'll try pushing on the connection and see if that helps. If not I guess I'll replace the module and/or coil.
 
#33 ·
Brandon, On the engine harness there is a resistor wire that goes to the positive side of the coil. I think it is white with black and purple stripes. This is the wire that needs to be replaced when using a MSD box. You can look at the fuse panel for ignition and run a 14 gauge wire from the blade in the fuse panel to the engine bay and connect to MSD box or remove the resistor wire from plastic connector using a paper clip and replace with the 14 gauge wire and connect to MSD box. http://www.msdignition.com/uploadedFiles/MSDIgnitioncom/Products/Ignitions/6420_instructions.pdf Check the diagram on page 11 to make sure you wired your MSD box and distributor correct. Here is an article to help you understand and repair the HEI distributor. It has some other useful info too. http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor
 
Discussion starter · #35 ·
Well, still running. I'm thinking maybe that one out of the three wire connectors that was loose in the plug that goes from the dist to the dist cap might have not been making good contact and once I pushed things together nice and tight that it solved the problem.
 
#36 ·
And we wonder why OEM's are building their cars with a coil for each plug and magnetic crank triggers, all controlled by computers with a limp-home-failure mode.
Good news Brandon. I was biting at the bit, (there's a term that was coined before cars) to tell my story with the same symptoms. The car would die like yours. Starting was a crap shoot after such a conkout. I checked everything. Really, everything, except the bulkhead connector under the power brake booster. In a BOAT YARD I borrowed a small crescent wrench. It still took about a half hour to get it off. Yep, the ignition pin was pushed and was laying on its side. SINCE NEW. I've no idea why it started to fail in the summer of '86. Fixed.
 
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#37 ·
Mine had the same problem driving along no issues then bang stalls. My dizzy had a connection to the MSD 6AL which was a push on connection and that's where my problem was and I cleaned it up applied a little die-electric grease problem is gone.
 
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