Disconnect the IPR then try to start, the PCM will take care of the oil pressure. If then it runs, look for chafed wireing in the harness were it could rub, seems to be a common problem. You have to attain 500 psi oil pressure to fire the injectors, also the cranking has to be fast enough, watch your tach when cranking, should be 500 RPM or above. I assume your oil level is OK. These engines pump a hugh volume of oil, if it is real low you could be sucking air.