I have an 06 6.0 I use mostly on weekends to tow a 26' 5th Wheel, the Truck has 56k miles on it and has ran great to this point. Now it will start fine when cold and runs fine, after getting it to operating temp it is hard to start? I have to crank on it for 25 to 30 seconds and it will fire and run great???

 

You probably have a high pressure oil system leak. This will cause the injectors not to work.
The 2 most likely causes are:
1) the STC fitting is leaking...there is an upgraded part to fix this
2) the stand pipes and dummy plugs are leaking...there are upgraded parts to fix them.

At about 65,000 miles my 06 began taking longer and longer to start. At about 80,000 miles, it left me stranded one evening. I towed it home...in the morning, after it had cooled off, it started just fine.
I replaced the stand pipes/dummy plugs and replaced the part that had the STC fitting and after initially taking about 5 cranks of 30 seconds each (to prime the high pressure oil system), the truck started right up in about 1 1/2 seconds. Now, at 115,000 miles, it's still starting good...problem solved.
The stand pipes and dummy plugs are about $100 for parts. The STC fitting kit is less than $100 (if I remember correctly). I did it myself, so labor was free for me. If you have a modest amount of mechanical skills, it can be done in a weekend. Mine took a week, however, I replaced a lot of other stuff at the same time.

Yours is a common failure for 05-07's...it's not whether these parts will fail, it's when. The upgraded parts should remedy this specific problem for the life of the vehicle.

 

Thank you very much bustedknuckles, I appreciate your reply. Where can I find a good repair manual that will show/explain how to make this repair? I am very interested in making the repairs on my truck myself and now is the best time to start

 

Here's a video on both STC fitting and stand pipes/dummy plugs:

I use ALLData for my manuals:
You pay something like 26.95 for a year subscription. It's cheaper after the initial fee. I subscribe for both my Toyota Highlander and my F250 for 5 years at a time at this point, since it's cheaper that way.

Good Luck...
Oh, I suggest using WD-40, then finish with liquid hand soap...it works great and it's less harsh than some of the gritty cleaners out there. Also, use nitrile gloves.

 

Too nice, thank you and i will let you know the outcome, you havew been a great help!
I have had some bad experiences with shops and don't want them "playing" with my truck!

 

I also hate taking my vehicles to someone else.
Haven't taken my vehicle to a shop unless I was forced to since a bad experience over 35 years ago. Took my Volvo to a shop, handed them a very expensive set of new shocks I bought and asked them to install them. Got the vehicle back, thinking they did what I asked. 3 years later got a call from a guy who bought my car, after I traded it in on a new one. Turns out he took the car to the same shop I did. He said the shop sold him a set of shocks. Turns out it was the same set of shocks they did not install on the car when I took it into them 3 years earlier. Talk about coincidence.
Name of the shop was Volpar in San Jose California. I love to tell everyone about this one. Like I say...fixed my cars myself whenever possible, from that point on.

Keep me up to date on your progress.

John