[buzzinhalfdozen]

Ed, I'll assume from the business you're in you have a DVOM? Hook it to the power supply circuit for your MSD or FAST unit, most have a record function to record high, low and average voltage set it to 1ms record speed and make a lap. If all looks well there, hook up to your crk. sensor circuit, also record set to AC voltage and monitor, a sudden change here would indicate an issue. Hoe are your Ign. components powered/ Relay, direct from switch? I have seen relays cut on and off due to points bounce, What sample rate does you datalogger have? Sorry for all the questions, just intrigued by the problem. Joe