[Gaz64]

Hi Brian,

It does sound like a ignition switch issue with both scenarios.

The MSD modules switches a primary voltage of 400-500 volts to the coil depending on model , but only when triggered by the distributor, as in engine spinning above 100 rpm.

If the module is somehow faulty, then it could be the reason for the on/off of the coil primary circuit.

Especially if the coil is hot with a cold engine that has not run for some time.

I would check to see what voltage is at the coil, be wary that the coil positive (orange) is at 400 volts plus with engine running normally, so be careful if this is in fact somehow "live", while the key is off.

I have replaced one ignition switch on one of my cars in 37 years.

But ignition switch failure is becoming more of an issue in some cars these days.

Gary