I had a 79 pickup with a/6 and it did something really weird to me one day.
I drove it to work and back, it ran fine.
I went home from work, hit the shower and was headed "out". Get in the truck and crank, crank, crank some more and no fire. I actually burnt out the starter trying to get it to start. Made no sense since it had run just fine about a 1/2 hour before and didn't die, I shut it off.
It started getting dark, I was still trying to start it with the good open, and then I saw a spark off the coil wire to of all places the upper radiator hose. (That's been 30 years ago, maybe it was a heater hose) I got out, moved that wire over 2" and it started right up. I needed a set of wires.
But of all places to ground out I still don't know how it would have been able to ground out to something made of rubber.... But it did