Coil Overheating

[Argess]

I just had some trouble with my car. Once well warmed up (20 to 30 minutes) it would die. It would crank, had fuel, but spark looked weak. Once things cooled down (another 20 to 30 minutes), it would start right up.

Since it was common to all cylinders, I suspected either the coil or the ignition module... after I checked all voltages, etc. What I found was that if I cooled the coil down by holding a wet rag against it and then pouring a cup of water over the coil, it would start right up. I confirmed this three times. Just let it idle until it died, then the water treatment on the coil. Started right up each time.

As it almost confirms a bad coil, I ordered another one, but am also wondering of the module might be malfunctioning... too much dwell and overheating the coil through lengthy primary current.

Now this system is a Pertronix Ignitor with a Pertronix 1.5 ohm coil (P/N 40011). I've never seen a coil fail when hot unless there's a break in the internal coil windings that spreads apart once it gets hot. This one does check out with no breaks although the high tension side resistance measures a bit lower than spec, and a bit lower than that when hot.

A Google search reveals there does seem to be a number of people reporting a similar coil problem with Pertronix, but they all had problems early on. Mine has worked flawlessly for about 13 years.

So no real questions from me. Just wanted to share as coil issues are seldom the reason for ignition problems. Usually dist cap, rotor button, wires or plugs. Anyway, comments welcome, especially if you’ve had a similar problem before.