[Greg Reimer 7376]

Art- I think I understand your description of your system, a few things caught my attention. A crank position sensor or cam position sensor, (reluctor) creates a sine wave that is very low amperage. It is discernable by an ECU, but probably not much else, since the signal is probably in small fractions of an amp. Not enough to run an auxillary circuit like the pick up of a timing light. The ECU reading the falling part of the signal( probably the point where the signal has just peaked and is now falling downhill after the trigger wheel tooth last excited the sensor has little to do with a timing light event. The timing lights I've always used were run off the spark plug wire as the plug fires. That's all thats relevant here. It doesn't matter to your piston where the ECU reads the sensor signal. The only thing mattering in the cylinder is how many degrees BTDC the spark occurs.Cam sync has little or nothing to do with spark timing,since its based off of crank position anyway.