This has been a recurring problem. I have had a Mallory electronic ignition system in my 1.8L 1975 for the past 4 years. It has continually plagued me bad experiences that end with a tow because of know spark. I’m now ready to trash it and go back to a stock ignition system.

Here’s my theory. The Mallory causes the engine timing to be off. This overheats the coil. The engine looses power, it misses, and then there’s one final gasp and no spark. Disaster ensues with a call to AAA. This latest episode happened with a new Bosch coil. The smell of something electrical smoking was very strong.

I can wait several hours after the coil has cooled down and it will fire right up. If not the timing, what else could overheat the coil like that? If anyone has had a similar experience I’d like to hear from you. Sleuths welcome.

Does it have near stock spark voltage and amps?

I once used a hi-powered mallory coil unit on a VW motor, fried the electronic points and distributor after about 4-5 hours of use... oops.

Yes it does.

CDI box burned up 2 of Kurt Donohoe's custom coils before it was determined the engine had defective wires without proper resistance. Changed them out and no more problems. I did run around with an oil filled Pertronix blaster coil without any issues.
Final solution also required swapping the BERU distributor ends with BREMI for a positive connection.

Here's a note I found he sent me:

1. Known problem with Beru shielded ignition wires, the connector where it plugs into the cap is too big, this results in creating an air gap that the spark has to jump to fire the plug because the conductors do not make physical contact. This will result in a double firing event when looking at it on the oscilloscope. Will result in CDI box and or coil damage if run for extended periods


2. Secondary resistance should be 10,000 ohms per cylinder, 1K between coil and distributor, 5K ignition rotor, combined 4k on the plug wires, 0 resistance spark plugs


3 Plug connectors while often go open circuit intermittently, check plugs connectors by removing from the wire and measuring using an ohm meter while gently tapping the connector against the side of the tool box or work bench. Plug connectors should remain steady at 3K +/- 10%, plug connectors that go open circuit or outside of that spec should be replaced.


4. Measure total wire resistance from the cap to the plug connector to confirm connection quality, specification should be 4K +/- 10%


5. Final ignition system check should be done using an oscilloscope to confirm all secondary wave forms are correct and there is no electrical ringing or errant patterns under load, (IE; the engine is running as opposed to just checking things with the engine off)


Click to view attachment

Solid wire spark plug wires?