Hello, I have a 90 F-150, I installed a reman engine in it a while back. Now while I'm driving it around, it will suddenly die. About an hour later it will start back up. Drive it a little more, and it dies again. It will sit and ilde all day long, but drive it, it will die. I have replaced the fuel filter, fuel relays, coil and starter relay. Also now, when I turn off the ignition, the truck keeps running. I have to pull the coil wire to shut it off. Could these two problems be related?

 

Read this thread.

 

I had the same problem with my 90 model,The problem was the ignition switch that is mounted on the sreering column.