Hello Walter,
BCS wrote:
Yes the ignition (as the the key) doesn't turn off but when the
engine quits running the ignition system (as in the magneto or that
block of epoxy and silicon under the hood) quits triggering the
spark. Tie into that.
Trying to determine if the distributor is no longer turning is a
non-trivial circuit. Best to stick with simple things when dealing
with safety issues. The inertial switch is pretty darned simple, it's
just a ball stuck on the end of a magnet. Knock it hard, it falls off
the magnet, opening the circuit.
If you can find the right spot to tie into all you need is an event failure
alarm
http://www.elektropage.com/default.asp?page=sub&bid=1&sid=18
A voltage divider across the points for a magneto should work. A more modern
system should be even easier as they probably have a low voltage wire somewhere
that will work.
Of course all the motivations change if your driving in a race.