I was helping a neighbor diagnosis his 99 Powerstroke today. He had an issue where the truck lost power and would not restart hot. He replaced the IPR and the ICP, checked fuel, replaced fuel filter, checked fuel pump. I ran some diagnostics on the truck with AE and truck is very slow to build HP oil when cold and the duty cycle had to go to like 60% before it could build 500psi to fire the injectors. When hot it will only got to just under 400psi and spikes the duty cycle to 65% with no start. Buzz test passes fine but contribution fails number 8 only every time. There were codes after the drive cycle for low/high inj pressure and inj pressure delta. Truck runs OK but duty cycle looks high to me for conditions.
My diagnosis is most likely leaking injector O-rings with number 8 be the place to look first. HPOP was replaced a year and a half ago due to a fitting failure in the pump. What do you guys say?
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