What coil..?

BTW.. .one thing I realized is that I did my coil voltage testing (to see that large - voltage excursion) on a points ignition. So I am wrong to make a solid conclusion on the ECU's output protection; the shunt snubber diode across the ECU output is possible. If is has one, then you can put a VM in diode test mode and will see the output just 1 diode drop from the ground (case) with the - lead on the output and the + lead on the case.