Used on the 60, 70 and 80 series.
Might also be found on a Dyna.
You can open up the relay to see what's going on.
Make certain you're fusible link is good. Try running a wire from your battery to the relay if in doubt as a test. I have a secondary fused line with a momentary switch which allows me to start or bump engine using 12 volts.
The relays seem fairly stout.
After sitting a couple days it turned over, started, but the starter kept running. Turned off the truck and the starter stopped after another couple seconds. I'm reading thats the sign of a faulty SR? The same issue happened maybe twice over the last 6 months where the starter would keep running for a couple seconds but I didn't realize thats what it was. Oof