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

Starters draw down the battery voltage during cranking to about 8 volts.
The 7 year old battery that was in car when this first began was 10.5 volts when cranking. Bought new battery and its 11 volts when cranking and 12.5 volts at rest. Hopefully I can get back out in garage soon to insure during cranking where is that voltage drop to coil happening. Most likely at bulk head connector but need to measure along path of circuit to find where that drop occurs. Full battery voltage should go through bulk head and back out via Ign 2 circuit and its not. But got stumped on 'I Got Zero Ohms cant be wiring' mind set and thinking like that isn't gonna get the car fixed....