Got a 97 f350 135,000 miles. Been cared for. Was towed in for no start, glow plug relay bad, replaced the glow plug relay and 2 new batteries. Will crank with slow to build icp at least 5 seconds of cranking after it sits for a while if try to start again right away will start right up. Leave it 15 min or so and the same thing. I have tried blocking the heads and don't have the tool for the left head icp adapter. Blocking the right head seems to start ok little quicker. Removed the ipr to inspect the o-rings ok. No oil in the fuel filter housing. How do I determine if its an icp? ipr? or hp oil system problem?