Testing the starter motor becomes a whole lot easier when you know where power should run to when you turn the key and try to crank the engine. So, hopefully my simplified starter motor system wiring diagram will help you.
I've made an effort to keep it in an easy to read style and it applies to the 1992, 1993, and 1994 3.0L Ford Ranger pick-up.
NOTE: The above wiring diagram applies only to the 1992 and 1993 automatic transmission equipped 3.0L V6 Ford Ranger. In the next page is the wirind diagram for the manual transmission equipped 3.0L V6 Ford Ranger.
You can find the starter motor test explained here: How To Test The Starter Motor (1992-1994 3.0L Ford Ranger).