Bench test the starter...
Using a fully charged 12 volt car battery... with extreme care, short circuit or connections coming undone during this test will flame-on, Instantly.
~Secure the starter to something solid, it will JUMP due to the rotating forces involved upon run-up.
~connect the black clip of the jumper cable to the starter housing.
~With a good set of jumper cables, connect the starter +power (usually M8 threaded stud) to red clip of the jumper cable.
~Connect a small jumper wire from the starter solenoid connector, this is usually a push on spade connector or smaller M5 / M4 stud on the solenoid housing, other end of this wire is bare and kept far away from all else in this lash up.
~Connect the red jumper cable clip to the battery positive terminal, connect the black jumper cable clip to the battery negative terminal..
~Touch the bare end of the wire from the solenoid connection to the battery positive power on the starter, if all is good, the starter will jump-run.
Bernice