It got down to 43 degrees a couple nights and the truck didnt want to start took forever, but when its warm it is fine, I am wondering if the glow plugs are bad becasue once it starts up runs perfect. What are your guys thoughts?

 

Do a FICM test. It's easy and quick. Just google search 6.0 FICM test and repair. How are your batteries?

 

I checked the FICM it tested fine and I plugged it in last night and it fired right up with no hesitation at all this morning.

 

Sounds like glow plugs then. I believe there is a way to test them with a multi-meter, let me see what I can find for you.

Found this:

There are 2 jumper harnesses that run down the side of each cyl head and connect to the main engine harness, dis-connect the connector and check resistance the resistance should be between 1 and 2 ohms

I'll keep looking and see what else I can find.


EDIT*

Attached "hardstart" PDF from Ford... walks you through testing on hard starts.

With that said, glowplugs almost never go bad on these.