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Old 10-09-2012, 09:11 AM
Bigdawg0114 Bigdawg0114 is offline
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Default MSD Issue or Not? Tech Support says no

Im running a 6AL on my 66 Chevelle - 496 stroker.

A few months back I began having an issue with cylinders not firing intermittently. It was typically the #1 or #2 cylinder, sometimes both, and ONLY on cold starting. After a few minutes the dead cylinders would start firing, though inconsistently at first, then would even out & the engine then runs fine. I replaced the distributor AND plug wires, thinking one or both to be the culprit however the problem is still present. So yesterday at cold start & with the problem present, I put a timing gun on each plug wire. I noticed that #2 was dead but #4 next to it was getting double the spark that it normally would, and the same on the opposite side of the motor with #3 dead but #5 firing like crazy. Once the motor warmed up all cylinders were firing steadily. One important fact to note is that with any dead cylinder, if I pull either the plug end of the wire off or the distributor end, a good spark with arch from the wire to the plug or distributor (depending in which side I pulled) and that cylinder will then fire fine.

Tech support says its either the distributor and/or plug wires in their opinion and no chance it's the MSD or coil.

Agree or disagree? Opinions and any tech support anyone could offer would be greatly appreciated
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Old 10-09-2012, 10:03 AM
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msdtech1955 msdtech1955 is offline
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well, the unit cannot pick on "certain" cylinders...it gets the signal from the reluctor on the distributor and sends "8" pulses to the box.

whats ,. interesting...
Quote:
I replaced the distributor AND plug wires
what distributor and wires..? ( also how old?)
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Old 10-09-2012, 08:39 PM
Bigdawg0114 Bigdawg0114 is offline
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I was originally running a Mallory Unilite distributor & Taylor 409 Spiro racing wires (10.4mm). I switched to a new Mallory Uniliye with a set of Mallory Pro Sidewinder 8mm racing wires - the problem remained the same regardless.

I'm wondering if I'm getting humidity build up inside the cap causing ionization & spark scatter which eventually clears up as the motor runs & warms up?? I've never had that issue before so I don't really know if these symptoms I'm experiencing would match those of ionization...
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Old 10-10-2012, 03:00 AM
Gaz64 Gaz64 is offline
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What spark plugs, and what gap are you running?
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Old 10-10-2012, 05:34 AM
Bigdawg0114 Bigdawg0114 is offline
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Well that theory's been ruled out, as I just realized that the new distributor wouldn't have had a moisture issue when I installed it new out of the box and the same problem existed.
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Old 10-10-2012, 05:41 AM
Bigdawg0114 Bigdawg0114 is offline
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Autolite Racing plugs @ .045 - I can't recall which one off the top of my head but I did switch up to a hotter plug when the problem started.
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Old 10-10-2012, 08:10 AM
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shoot a pics of the install, maybe i can catch something .
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Old 10-20-2012, 07:18 PM
Bigdawg0114 Bigdawg0114 is offline
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@MSDTech: Your answer regarding how the MSD picks up the signal from the distributor is basically what the technician told me by phone as well, however he ("Peter") seemed very disinterested in talking about it much beyond that so I just hung up. Today, out of complete frustration I decided to remove the MSD from the car all together and then just wired the ignition as stock, using only the distributor, coil & ballist resistor. The car ran fine. So I guess my question is now - isn't the problem narrowed to most definately the MSD at this point?? Stupid of me not to mention this until now but I failed to previously advise that I also have an MSD timing advance box installed as well. Could that potentially play a part in my issue?? Neither was wired in when I ran the car today and like I said, it started and ran fine without them.

Is it not at all possible that the MSD is not be sending the 8 pulses? I mean, isn't it essentially a "computer" that could malfunction over time just like any other (my unit is approx 15 yrs old)? I don't know much about the inner workings of the unit but it sure seems to me that the MSD is essentially the brains of the ignition system and that, with a new distributor & wires in place, the only things left would be it, or the coil. I did find a bad plug along the way which I replaced. Right now the car sits with nothing more than the stock ignition system in place and it starts right up and all cylinders and firing away! But I do have a new 6AL sitting in the box ready to go which I plan on installing tomorrow. just was hoping to get your opinion before I do so and potentially hit the same problem as before.
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Old 10-20-2012, 10:35 PM
Gaz64 Gaz64 is offline
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I'd be looking at the pickup airgap to see if you have a non-concentric reluctor wheel.

Your firing order of 1-8-4-3-6-5-7-2 has cylinder 1 after cylinder 2.

If the airgap is too big, one or more cylinders would misfire.

And personally I would never use components from different manufacturers.

My ignition systems are all MSD, my fuel system plumbing is Earl's, etc.
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Last edited by Gaz64; 10-20-2012 at 10:39 PM.
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Old 10-20-2012, 11:38 PM
Bigdawg0114 Bigdawg0114 is offline
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Gaz - I replaced the distributor & spark plug wires and the problem continued. I would think that you're suggestion would be possible if I hadn't yet replaced the distributor, but what are the chances that would be the issue with both the old & new distributor? Also, as I stated in my previous post, the car starts & runs just fine with the ignition currently wired as stock setup, so I figured it was now a certainty that the MSD was the culprit.

As for using different brand components, I don't necessarily disagree with you on that... but the MSD installation instructions have a diagram specifically for the use of a Mallory UniLite distributor.

Thanks for your input, every bit counts!
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