magneto issues

[SteveG]

Just when I thought I had experienced yet another unique failure mode I read a very similar story added by our own Mouseketeer "El queso grande" to the thread about a plane down in Montana in which he secured an engine due to a mag failure attributed to loose screws due to deferred maintenance. I've just experienced the same failure but after only 68 hrs. since a comprehensive inspection and rebuild by a well known magneto specialty shop. I'll skip over the blow by blow details of the flight and address the crux of the issue. In troubleshooting the problem I found the mag loose but not in the manner one might expect. The drive half of the mag was still securely clamped to the engine case but the distributor half was loose. All five case half securing screws had partially backed out. Thinking I had identified the cause of the misfire and suspecting distributor drive gear damage, the mag was pulled off and inspected. Although the housing halves had come partially apart no internal damage was noted. But looking further and opening the points compartment it was found that the screw securing the condenser had completely backed out and was just rattling around within, randomly shorting out the points and causing havoc with the ignition sequence. And so, the moral of the story is keep an eye on your magnetos regardless of time in service lest you find yourself with a very unhappy engine.