Next time you go to start the truck turn the key to on position and wait 5 seconds, shut off, then try to start. If it starts quicker then it is a pump prime pressure problem. This could be pressure bleeding back thru the pump or out of the injectors. If it is leaking out of the injectors then it could be flooding a little and needs to run to clear them out. To test that you need to hold foot to the floor when inital cranking and it will keep any additional fuel from entering cylinders.