IPR valves are Injection Pressure Regulating valves that are used to control the high pressure oil limits on Powerstroke diesel engines. It is a good idea for rebuilt diesel engines to be fitted with new IPR valves. A faulty IPR valve can lead to hard start on no-start on Ford 7.3L engines and other Powerstroke engines such as Navistar diesel engines. DSG rebuilt diesel engines can be supplied with new IPR valves to ensure good starting.