First I would make sure the lift pump is working all the time check the ground carefully! Next time it does ut without doing anything else crack the bleeder and manualy prime it. Check all the grounds on the truck, im assuming there isn't any codes. If all that checks out possibly the ficm is bad but I don't know for sure? Just throwing things out there to try and hopefully hit it sooner or later
. What is the rail pressure at? Could it possibly be a failing cp3 or maybe a fpr?
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