[Jack21]

Petek, dumb question. You show ignition module as red wire to coil+, black wire to coil-, and an engine ground also to coil-. Not sure coil primary- is supposed to be grounded, but should go back to the box only. CD's pulse the coil at 460 - 480 volts, as opposed to conventional ignition at 7 - 12 volts.

Black wire on distributor is a ground on distributor advance plate. On the Duraspark, it is present, although the pickup coil is not grounded through the distributor. On the MSD there are only two wires, and no ground. Only rationale for a ground wire would be radio static, or to insure that any induced voltage that creeps in gets grounded to avoid timing errors.