Big shout out all you deisel fanatics im new to the deisel world 2 deisel truck my first ford but im having an issue i bought a 2004 ford f350 6.0 dually dont realy know much about the truck other than it was rebuilt engine about 80xxx miles ago well here i go every morning (cold)with out a dought this truck will start right up runs and drives great no problems shifts great idles perfect 70-80 down the freeway no issues the problem is when i turn it off it will not turn back on it cranks but will not turn on iv used starter fluid in the air filter and it will crank right up i know i know its bad for the deisel but i had no other option i have read about the ficm and how to check it and i did good 47v to 48v, tested batterys and they tested good disconnected and reconnected the ipc senser on passangers side valve cover cause thats what i had read up to try but it still does the same thing does any body have any idea what could be the cause of this or what to try to figure out the problem.

 

The best troubleshooting tools I added to my PSD were mechanical pressure guages. One for the high-pressure oil (3500psi), and one for fuel (100psi). One for lube oil is a good idea too. Without these, diagnosis is a total guessing game.

Just a guess, but you may be losing hpop pressure due to bad/worn injector o-rings, or the hpop itself. Cold thick oil may still build enough pressure for starting, but hot thin oil is not.