First, Does your truck have a CAT hand priming pump on it?

If not, buy one and its gasket and install it = it also two one-way check valves in it and will help with start-ups.

Part # 137-5541 for the hand pump
Part # 1P0436 for the gasket
{should be able to reuse the bolts that hold on the little cover, that is currently there.}


Now, if you already have a hand priming pump installed, on your engine, The next suggestion is to replace your "fuel return line check valve" IF you have to later style fuel block on your engine (you didn't give me a CAT engine serial number and/or year of truck , so I am guessing)
Return line check valve is #5 in the first photo, that I will add. DON'T OVERTIGHTEN, just needs to be snugged up.

(C-12 fuel system_later 2KS version.gif)

C-12 fuel system_later 2KS version.gif (11KB - 288 downloads)

C-12 hand pump with 90 degree adapter.pdf (71KB - 451 downloads)