Hey everyone, first post. Have an issue that I haven't started tracking yet and I wanted to run it past everyone in case it's common, saving troubleshooting time.

1991 F150 Extended Cab automatic 5.8L... Two times now when the truck is well and warm and I've went in to reverse to back up it dies. Then it seems it won't start again until I let "it" cool off. Unsure what "it" is that cools off to allow it to start again. It seems to sound like the batteries dead when I try to restart it, slow incomplete cranking. But, I've also found a relatively large front main seal leak lately that I've been feeding for a bit. Hoping the issue is not metal to metal seizure. Maybe transmission? Maybe battery draw from low RPM, brake lights, and such in reverse? My money's on battery, planning on having it checked/replaced today perhaps, but wanting to get any other ideas. I'm sure there's lots of sensors and such that could cause similar issues. Thanks for any response.

Update... It seems that the truck gets harder to start as it heats up.

 

One thing to check is under the distributor cap. I had a problem starting and it turned out that there was water under there. A drying with paper towel and it started easily. Any check engine light?

 

maybe weak battery or corroded connection.
Battery will show weakness when real cold or hot.

 

There could be an issue in your transmission as well. The IAC (Idle Air Control) sensor could be the culprit. Remove the IAC and clean it. If that doesn’t fix the problem then replace it with a new one.