Short version: 2014 f250 takes about 10 seconds of cranking to finally build 5000 psi fuel to start. when it starts it runs really rough and makes a squealing + knocking sound like a spun rod bearing. Truck started fast and ran fine then this suddenly started. Is this a failing high pressure fuel pump or something else?

Long version:

I have a 2014 f250 that I just picked up from auction so i dont know the history. It started quickly and consitnely for a couple days in my shop, no obvious issues. First test drive it was driving fine down the road for about 3 miles then i slowed down to pull a u turn and the truck just died, no sounds. tried to crank it and the engine acted like it was locked up. only code was a cylinder 3 contribution code. I pulled the 3 injector and tried to crank engine, still locked. 2 new batteries, still locked. waited till the next day then the truck started to crank "fine" but would not start because low fuel pressure. after lots of cranking it did start but runs very badly.

Hi, did you ever figure this issue out?

I would start with the fuel filter. I've changed them out and everything seemed fine...until I put a few miles on it and got the low fuel pressure warning. If that green o-ring isn't lubed well with a little oil, oftentimes it won't seal.

Can you share a video of you trying to start it? The symptoms you listed could be a fuel pump failing, fuel filter clogged/ not sealed, bad sensor(s), internal damage, or a long list of random things from a shorted wire in a harness to a cracked injector or bad control module.

Pull the upper and lower intake manifold off and pop the regulator out and see if there’s metal on it.
Also I’d cut the oil filter open and search for metal because no cp4 is going to lock the engine up. Any time I’ve heard a 6.7 make noises like that it got an engine. However, I had an lml that the customer said it squealed as well prior to dying... it’s currently getting a fuel system. Cp4 had come apart.