I know that we need 500 PSI for the engine to start, so what should the IRP be at when starting? 100%? Something less? And if 270 IPC is 65% IPR, what would I expect IPR to be with 300 PSI on the IPC cranking?i have replaced a 1999 7.3 with a 2000 model engine. The engine will only start if you use starting fluid. after starting with starting fluid the engine runs fine until it starts warming up and then it begins to run ruff and will stall after it warms. During cranking the icp starts at 0 for several seconds and finally works up to about 270 with a 65% duty cycle on the IPR. we bought a new icp pump and have the same results. New oil and filter, new fuel filter, checked glow plugs. Have not bought new IPR but swapped the one from old engine and one on new engine with no change. When you start the truck when it is cold with starting fluid the icp pressure shows about 650 to 700 during idle. As it warms, it begins to fall to the low 500's and lower and begins to run ruff and stalls. over the last 2 weeks the truck has started about 7 times with out starting fluid but it is random and we can't figure out why. It appears we are loosing oil pressure, can someone point me in the right direction?