you might want to check the injector filter and see if it's clogged up.
depending on which year it was built there are a couple of injector body's it might have.
that injector filter is located underneath a small plate or sensor on top of the injector body or inside the inlet hose elbow.

just remove the 2 screws holding the cover, sensor or elbow and look inside and there should be a small 10 micron screen filter inside held with a clip.
the manual recommends replacing it but you can try to clean it and see if that makes any difference in starting.

also you can remove the drain plug on the vaporizer and see if it has any oil in it and clean that out.
If all of the above fails to help the starting you may be looking at a bad injector.

it is highly unusual that it is not coding out since these trucks are fairly sensitive and code out with any irregular pressure or fuel delivery issue.