The truck timing is on letter c on the pump gear at top dead center with the engine. The timing on the out side is stock I think maybe the pump is getting worn. Hey it only dose this when it's cold it starts fine when it's warm out so I don't think it's the lift pump and their are no diesel leaks. But if u let the intake heater have two revolutions instead of one it will start with ease is the intake heater weak????

 

Sounds like the whole engine might be getting tired. First check for voltage drops through the battery cables under cranking conditions, and check the voltage at the starter. If the electrical end of it checks out good, do a compression check.

 

i wouldnt worry i always do 2 rev on mine when its cold its like for the engine