Cranks but won't start. Unplug ground at field spade on Alternator and it starts?

340sFastback said

Battery when cranking - 10.5 volts
Voltage at + side of coil when cranking: 8.5 volts (does not start

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That proves the IGN 2 is not providing battery voltage to the coil plus during cranking.

Why is the big question.