2003 2500hd warm engine starting problems
 

I have a 2003 2500hd pickup with the 6.0 engine, it currently has 65k miles on it.

When I first got it (used) in 2004 it was in perfect mechanical condition.
It always started immediately with the crack of the key!

Over time I would have to crank it longer before it started.

For the last 18 months or so, it started ok when the engineis cold, but when the engine is warm I have an intermittent starting problem. BTW, it isn't throwing any codes.

I'll turn the key andcrank itfor 10 seconds or so, no start, try it again maybe itwill start.

Usually it takes three attempts before it will finally startup (keep in mind this is only when the engine is warm) and it sputters like it's going to stall then it's ok!

This condition is less of an issue in the winter, and much more of an issue in the hot summer weather where at times, first thing in the morning with a cold engine it will take 3 attempts of cranking before it finally starts!!!

So heat seems to be the culprit here,or so I'm guessing.

The truck idles and drive great so I don't think it's a tune-up issue.
I replace the fuel filter every year, changed the plugs last year, and have checked the fuel pressure regulator (when it doesn't start with the first try) to see if fuel is leaking from the hose and it isn't. So I think I can rule these things out. My only other guess is a failing fuel pump, although I pressure tested it last year and it had around 50 psi. And can a failing fuel pump take this long to go?

Other thoughts are cam position sensor or crankshaft position sensor, but again I scanned it and no codes!

Anyone else had this issue and / or know what the problem might be?