I have an intermittent problem on my 1970 SIIa, petrol.
Perhaps 1 in every 200 starts the truck will fire up but the starter will not shut off. This is how my previous starter got burned up, with my frantic wife on the phone to me when it happened to her...I tried to guide her as I listened to my poor starter slowly die in the background.
That was the first time it happened. Needless to say, I replaced the starter after that (eventually, after a failed original style starter [unrelated to the above problem], I replaced it with a nice hi torque starter rather than the original -- highly recommended). Maybe 200 starts later with the new starter in place it happened again. Fortunately I was driving. I hopped out and disconnected the battery ground cable. Put it back on and all was again fine.
After that incident I replaced the solenoid (most likely culprit I figured) and the ignition switch (also makes sense). Later, I also replaced battery and starter ground cables. Everything else seems in good order.
It still happens, though. So far, it's been me driving but eventually it will be the wifey and I'm not optimistic she'll be able to hoist the hood (spare attached) and yank the ground cable in time.
Also, today's incident (happened again) had a new twist -- disconnecting the ground cable didn't remedy the situation. Of course, the starter stopped turning over, but when I reconnected the ground cable it was back at it. To break the circuit today I had to remove the positive battery cable (truck is neg ground) from the solenoid, then it behaved normally after reconnection.
So, I think I clearly have a short (I'm assuming my new solenoid and ignition switch are working consistently), but how to detect it since it only happens so infrequently?
Any ideas or other thoughts are welcome. Thanks in advance.