Hello folks,

In my endless piddling I finally caused myself a problem. To troubleshoot it I need to know which of the two wires emerging from a stock Mopar electronic dizzy is considered (+) and which is considered (-).

I have several NOS dizzies and some have a red wire and a white wire, some have a black and a white wire. I wouldn't just assume black = red = (+). I would like to know the basis for the nomenclature because logically both wires connecting to the pickup have connection to the dizzy body, thus are grounded (-)...right?

The reason I need to know the difference is because in wiring up a MSD 6a system one is directed to run the dizzy (+) wire to one place and the dizzy (-) to another place. I installed the MSD 6a system as one of three ignition systems I have wired in, followed the MSD diagram and bought the tach triggger for the MSD 6a. Upon a road test yesterday the vehicle started perfectly, ran great for about 1/2 mile, then died by slowly dwindling down power and rpm. In the few minutes it took to pull out the VOM and check voltages, then try a restart, engine started as if nothing had happened, then died as before, about 3 minutes of driving.

So I swapped the dizzy leads to the MSD purple and green wires, ran fine, just as before, failed just as before. Having no more time waste on it yesterday I just pulled out the dizzy running MSD and plugged my "cab stock" spare electronic dizzy into my GM HEI module wiring and cruised on home.

When I intially installed the GM HEI module it was as others have said...no doubt as to which way the dizzy wires should hook up! Well, without knowing (+) and (-) I can't trouble shoot the MSD effectively....sure I can fumble around, but I would rather reason this out in the house first.

Any ideas, polarity or MSD wise!

Thanks
rock
'64d100

IIRC they are not actually + or -, just that one reads the front edge of the reluctor and the other reads the rear edge.

I know that if you reverse the wires it will change the timing almost 30 degrees. I have done it with my MSD just to see what it did.

It should not cause the problem you're having unless the pickup is bad.

_________________
Official Cookie and Mater Tormentor.

Slantzilla is correct; the signal from a Mopar distributor is a bit more complicated than a simple positive and negative. The wrong polarity will throw your timing off and cause the timing to retard more at high RPM, but it usually still fires.

It sounds like you have an overheating problem, and this is much more likely to happen to an MSD box than a pick-up coil.

_________________
"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

keep an air duster wit you and go for a test drive, when it does this blow it off to cool it and see if it fires up

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'72 Valiant DD for over a decade-225-Disc brakes, big T-bars, big Sway bars f/r, carter bbd/super six, GM HEI, 2- 12" subs in trunk, 1000w amp...
'77 cherokee cheif widetrack-360-33x12.5 tires-no lift. keeps driveway dry-project/backup DD/mudder