The fuel pressure on the Ford Powerstroke 7.3 Diesel is very critical. This is one of the first things that should be checked when drivability issues are be experienced. The liquid filled gauge and extended hose allow for the operator to drive vehicle and read gauge under pressure. The fuel injectors on the 6.0L and 7.3L are designed to run at 65 plus psi The fuel cools the injector as well as lubricates the injector. If the engine is operated with low fuel pressure. Damage could be done to the injectors Oil Pressure The oil pressure on the Powerstroke 6.0L and 7.3L is very Important because the lube pump pressure supplies the high pressure oil pump with oil.