Are you 100% SURE you have both a good engine ground and especially a GOOD ground to the ECU box on the firewall? very critical.
Also, what is the voltage at the ignition coil+ when the key is turned to the "ON" position, not start position? Then check the voltage at the + terminal on the coil when it is running?
Also make sure yu dont have an ECU power wire running near a spark plug wire etc. Your "crazy" erratic readings may be some some of voltage spikes from other sources etc.
RIP Monte Smith
Your work is a reflection of yourself, autograph it with quality.
WD for Diamond Pistons,Sidewinder cylinder heads, Wiseco, K1 rods and cranks,BAM lifters, Morel lifters, Molnar Technologies, Harland Sharp, Pro Gear, Cometic, King Engine Bearings and many others.
| 
