Starter keeps running

Except my relay contacts didn't weld shut. I used the original relay for another 15 yrs (when car was stolen). The stater's solenoid contacts also didn't weld shut since the solenoid would still clunk, and released when I disconnected the battery. I suspected the solenoid was getting energized via the 12 V starter supply (once actuated), so it stayed on when the starter relay released, though I couldn't see how that could happen. I wasn't too electrical savy in those days (mech engr degrees), so gave up and bought another starter, which fixed the problem.

The other time I dealt with a starter issue was when it would clunk but not apply power to the motor. I was stranded at the Grand Canyon on a cross-country trip and had to pay $100 for a new starter (~$400 in today's dollars) and wait all day for it to come on the "water truck". In the interim, I took the starter apart and found the solenoid's contacts pitted. I tried adding a shim washer under a contact, but didn't work. I wish I had known the hill-billy "fix" of wacking the starter with a hammer. At least this was a slant six, where the starter is very easy to replace. I wasted a lot of money on car repairs in my dumF kid days. At least I wasn't a young woman, who are even easier marks.