Was driving along today on a back road, and went over a few bumps as I started accelerating. The truck just turned itself off, no dash lights, no chimes, just like you'd turned the key off. I stopped and let it sit a few seconds, then cranked it right up and haven't had any problems since. Any ideas? Was kind of wondering about my key ring or a loose ignition switch, the key ring is kind of heavy I guess, and has a carabiner on it. Could that cause problems?

 

loose battery connection, failing accessory relay, ignition switch.

 

I had a problem with one of my longer ford keys sometimes catching the hole in the back of the steering wheel. When I would make a right turn, it would kill the truck, and try to lock the steering wheel. I would straighten it out and it would come back to life. Since I was usually accelerating when this happened, the engine never really died, but it was a bit scary. After about 5 times, and after selling my ranger, I got rid of the key. It had a pretty good bend in it. Loose anything thing that could catch there, and see if that helps. I wouldn't think weight (within reason) would do this, but you never know.