Starter keeps running

The starter itself can do this in certain circumstances. In my dumer-F kid days, I dis-assembled the starter in my 69 Dart to fix (recall installing a new solenoid). When I installed it, it would crank and not stop. I tried again, same thing. Gave up and bought a rebuilt one. Today I wouldn't fool with fixing one. Starters were expensive in those days (~1980). But, it could still have been the relay. Perhaps the old starter drew enough current that it somehow caused the relay to latch.