Blue don't overthink. The box is grounded and there are 4 wires. 2X are the pickup, the black is coil NEG and the one left over is power
From what I remember, and what you and I suspect it seems to me
If you can get it to quit........
1...Immediately measure coil neg which should be low, couple of volts and lower the better
2...And measure coil + which should be 6-8 but lower than 12
In other words the coil neg might be low, ok, but if the coil does not have power on the + side, of course it will be low. You are trying to determine if the coil has power AND is drawing current.
If the coil + is high, and the coil neg is also high, then the coil is not drawing power. This indicates box problems or box wiring/ no power
3...Run the "tap test" and see if you have a good spark at the coil secondary spark tester
4...If not, probe the rear of the ECU power lead and see if it has power. But remember, if the coil voltages are OK, that implies that the box is at least partly OK or the coil would not be drawing current.
If the box has power, the coil voltages indicate the coil is drawing power, but the tap test gives you no spark, it almost has to be either the ignition system harness or a bad box.
If it passes the tap test, this implies a bad pickup. However, there are rare cases where the thing will pass the tap test, but the trigger circuit in the box is AFU and won't trigger from the pickup.
So at that point, change the box.
