Connect the input to an o-scope. Remember the coil and capacitor act as an oscillator. If the spark plugs are not easy to fire (possibly gapped too wide or fouled), there will be multiple peaks in the voltage. It is a design feature, if the plug doesn't fire on the first peak, it might fire on the second, third, etc.
Reminds me of a class project some other students were doing in a mechatronics class I took. They were trying to do timing adjustment with RPM using a signal from the distributor that was measured using a Motorola 68HC11 microcontroller. Their system worked perfectly using a signal generator to generate the input, but when they hooked it up to the test distributor the signal was to noisy to use. -- wesley scott k...@spottedowl.biz > > By the way, I never could get the Tiny Tach (my THIRD one) to read anything > but gibberish. One minute it's almost accurate, five seconds later it's > reading triple what it should, then twice, then 1.3x, etc. It's not even > linear or a proportional reading of real engine speed. It's useless in my > plane, despite doing everything the manufacturer can think of to make it > work, and despite the ads which say "works with any points and distributor > system". I've bought and paid for three of them now, and have nothing but > an expensive hour meter in my panel to show for it...and it doesn't even > read tenths of an hour... > > Mark Langford, Huntsville, Alabama > N56ML "at" hiwaay.net > see KR2S project at http://home.hiwaay.net/~langford
