Hey guys I’ve got a 90 Cummins and somethings going on with the ignition. When it’s cold in the cab the key will turn but is very stiff and my truck won’t start. So I jump start it and drive around, and once the cab is warmed up the truck will start using the ignition. Any ideas what would cause this? I have replaced the ignition switch and bypassed the neural safety switch.

 

Lock cylinder.

The engine is MUCH easier to turn over when it's warm. Need to have your batteries tested?