I have a 2003 F250 that won't start. We've replaced the ignition switch and the starter. It went for a while where it would start sometimes and then not start. Now it won't start at all. Any ideas what else it could be?

 

Welcome to the site.,

So we’re all on the same page,, the engine won’t crank over, resulting in a no start...

 

That's correct. It won't crank and it doesn't click. We replaced the lock cylinder today and that didnt fix it either.

 

Will it crank in neutral? Assuming an auto.. If yes, the DTR (digital trans range sensor) is failed.

Possibly the starter relay in the Central Junction Box (CJB), and a ignition switch ‘input’ ( start/crank) as well as on through a good DTR can be proved out to the starter relay connector with the relay removed,, possible fuse/s, and should be checked..
But if you have a 12v test light I can give you some quick illustrated check/steps to better diagnose..
If the start/crank function is missing at the stater solenoid, more than likely an issue noted above..
It will crank if jumping the solenoid? If not,, chances are a starter issue..

 

It won't crank in neutral. We've replaced the starter, lock cylinder and ignition switch and checked the relays. It will start by using the switch directly on the ignition switch box (turning the key to unlock the steering wheel).