Originally Posted by Coupe
If you wired it like this...
And it hangs, it may just be the teeth meshing together in a bind and holding the Bendix out, and if that Bendix is out it will keep running.
IMO unless the car is still running points or some other ignition that requires a 12V start and a reduced voltage for the run circuit, I would generally avoid running the stock solenoid to activate the start circuit of the replacement starter, and/or totally eliminating the use of the stock solenoid for anything other than a junction block. (and even if the "S" circuit is needed, I would only CONSIDER using the stock solenoid for this purpose ONLY, WHILE still NOT running the new starter solenoid wire through the old solenoid)
Using the stock solenoid to trigger the solenoid on the replacement starter adds needles complexity to the circuit, and thereby makes it less reliable.
I know that using the stock solenoid to trigger the replacement solenoid is sometimes recommended, but IMO it is just a bad idea. (this setup stacks Ford style solenoid reliability issues onto GM style reliability issues, making the circuit many times more likely to fail)
When I used a similar starter on my Lincoln (due to a tranny swap) I hooked up both solenoids as pictured above, it didn't work right, (the starter hung) then I thought about what I was doing and asked myself WHY? Wired in a traditional (GM) manner and it worked right.