Don't know if this helps anyone, but check you're electrical grounds!

[math1960]

I've gone through many starters over the years and always had problems with starting. I recently had a master mechanic, who used to work on these old CUCV's, do a thorough electrical check. He said I " wasn't getting much fire". So he put an industrial sized ground from under the dash to the chassis.
Man, that fixed everything. So far, this old m1009 has cranked like a CHAMP. Real strong starting. I even think my MPG is better if that's possible.
I always thought a engine setting on a chassis was good grounding, but I guess not.

 

[oboyjohn]

Having just the engine sitting on a frame doesn't mean it has good grounding. Don't forget the engine and tranny are sitting on rubber isolators ( mounts ), thus they have to have a ground running to the chassis. I have seen some very weird instances when grounds go bad. Once I had a truck with air shift/ electric solenoids for the transfer case, transmission, diff locks and inter axle lock loose the "master ground for all the soleniods. With the engine running, I would shift to first gear in Blackout mode and all was fine. But when I would turn on the driving lights and shift to first, the transfer case would shift to neutral! Surprising how electricity will almost always find a path to ground and in the process made unexpected circuits activate.

 

[135gmc]

And if you ever need new cables on something that's 6-volt, remember to always get "6-volt" cables -- they're much heavier than 12 volt cables. Check NAPA instead of one of the chain-store parts suppliers