When the truck isn't running the driver side power window works fine. When you start the truck and it running the driver window won't go down, it will go up but not down. Anyone ever come across this.

 

Ok, that's weird. Nothing really changes between engine running, or not.... power still comes from the same place, goes to the same place, via the same circuits. Test for voltage AT the window motor, engine running, and not. See what ya get.