Oil pressure issue 2005 F550
 

Can you have a large enough HPOP leak that you will not have any LP oil pressure?
Oil will fill up filter housing in about 6 seconds but do not have any pressure register on manual gauge. Any suggestions?

Yes it is very possible, especially if the STC fitting has failed. generally you will have a "hot no start" condition if you have a high pressure oil leak that is bad enough to cause low oil pressure. I would also check out the low pressure oil pump gears and the oil pressure regulator that sits just behind the balancer on the crank shaft.

Is there any other test to run on the HPOP besides the air test? I am going to do it today.

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I pressured the HPOP up through the ICP port. I could not hear any leaks and system held pressure for 60 seconds, did not loose any pressure at all. Now where do I need to look?