Initially I thought he was measuring one terminal that went from 12V to 8V back to 12V.
Now I see he has one constant 12V, and the other goes from 8V to 12V.
bad ground doesn't explain the 8V, which should normally be 0V I thought?
Ohming the coil ground is solid advice. It looks like that ground isn't really shared with anything but the rear washer.
(even a functioning rear washer doesn't mean the starter relay coil ground is good, possible broken wire as you both mention)
Ground Zone #5, Not sure where it's located exactly, somewhere on left front side of motor..
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