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Help Please...Engine Stalls For No Apparent Reason

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MikeN

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Discussion starter · #1 ·
I'm posting this in Performance rather than Troubleshooting because I run an MSD system that Performance guys may be more familiar with.

The last three times I have driven my Chevelle, it will crank up and run completely normally for several miles, and then go completely dead. After coasting for several seconds, it will suddenly start running normally again. It doesn't really act like fuel, because it doesn't sputter or anything like it's running out of gas. I am thinking it's an ignition problem. I run one of Dave Rays's small-body MSD trigger conversions, with an external MSD Blaster coil and MSD6AL box. I guess it could be fuel, I don't know...I am using a fairly new Holley 650DP #4777. I had a problem several months ago with a stuck needle and seat, but this was causing flooding, extremely rough idle, and stalling. The current trouble is really not similar at all. If anybody has any ideas, or can suggest a course of action to begin troubleshooting, it would be greatly appreciated.

Thanks,
Mike
 
#2 ·
not sure on MSD products.... but definitely sounds like some electrical problem.
i had a similar problem in our nova, it would just randomly cut out and come back on again.... turned out the wiring harness connection through the firewall had come loose just enough to disconnect at times. took me awhile to figure that one out. this was with a stock HEI system.
i would double check all your electrical connections as a start...
good luck.
 
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#3 ·
Could be modulator going bad.
 
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#4 ·
Originally posted by gared69:
Could be modulator going bad.
Click to expand...
If you mean the hei ignition module, I second this. I had a very similar problem happen to me out of the blue one day in town. I drove it for a few days, then it got to the point where I'd have to wait 5-30 min to get it to start again. The module was the cause. I don't know how Dave's kit mounts the module, but I'm sure you know that on a regular HEI its under the cap.
 
#5 ·
Before you go replacing parts do a little troubleshooting. Hook up a timing light and rest it between the hood and windshield. Drive it around until the problem happens. If you are losing fire then hook up a 12v bulb or voltmeter to the power wire to the hei, drive around until it happens. Light goes out, trace wireing back to source checking all connections. Light doesn't go out, troubleshoot ignition (I would repalce the module first).
 
Discussion starter · #8 ·
I emailed Dave Ray, and he was kind enough to offer his 2 cents. He thinks the culprit is almost certainly one of three things...bad coil, loose wire somewhere, or bad magnetic pickup in the distributor. There is no distributor module used with this particular conversion and MSD6AL, all the distributor really contains is the magnetic pickup if I understand correctly.

Towards the end of the racing season last year, I was having difficulting running as quick as I was in the earlier part of the year, and the car has taken to dieseling when I shut it off despite running the same timing and fuel that I have always run. I'm starting to wonder if the coil has been failing all along.
 
#10 ·
Is it dieseling or is it what MSD refers to as "engine run-on" due to the wiring between the alternator and the voltage regulator not having a capacitor installed correctly?

Possibly not getting a full 12volts to the ignition?
 
#11 ·
I've had this problem a couple of times. The first time, it ended up being the module in my Unilite distributor. The second time, it was my ignition switch that had gone bad. Both times the problem was intermitent and was a real pain in the arse to figure out. The tip above about wiring a bulb into the circuit is a great idea. Otherwise, you'll be like me and waiting for it to die completely before you can pinpoint the cause. Goodluck.
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Discussion starter · #12 ·
Adam, thanks for the offer, but I've got a buddy lending me a like-new Blaster coil. I'll try it out Saturday.

Joel, all my underhood wiring is new stuff from M&H, and they custom-fabbed it for MSD/HEI and internally regulated alternator, so I think it's OK unless I have a bad connection somewhere.

It will be saturday before I can experiment, but I'll let everyone know what I find. Thanks to everyone for all the hints, offers, and suggestions.
 
Discussion starter · #16 ·
The problem is solved...it was either a bad coil or a bad coil wire connection. MSD sells a little adapter that you can insert into the top of their Blaster coils that allows you to use a coil wire with HEI-style ends on it. When swapping the coil out, I noticed this adapter was pretty loose. Lazy on my part to have used the adapter instead of just fabbing up a coil wire that would work without the adapter. Car runs great now, and thanks to everyone who offered an opinion.
 
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MikeN
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