In Reply to: Ford 8N tractor starter won't disengage, Positive Drive type posted by Brad Cobb on March 08, 2020 at 21:01:31:
Figured I'd better put this discussion to bed. What was causing starter to continue turning (hung-up symptoms) once the 8N tractorís engine was running, turned out to be caused by a weak spring and corrosion.
Symptoms were traced to starter solenoidís sometimes remaining engaged, due to weak return spring having to work against corrosion inside the solenoid, and simply not being strong enough to overcome corrosion reliably. Intermittently keeping starter contacts energized despite engine running and starter button de-energized (not a happy scenario!)
Solution was to clean out solenoid, drill small hole in bottom solenoidís base plate to permit moisture drainage, and providing machine screws/nuts replacing rivets holding solenoid access plate closed, such making allowance for future servicing of starter solenoid if necessary.