Fuel Rail: Description and Operation
FUEL PRESSURE REGULATORFuel Pressure Regulator (FPR):
The Fuel Pressure Regulator (FPR), located on the fuel rail, controls the fuel pressure at the inlets of the fuel injectors. The FPR has an operational range of 33 - 44 psi and is controlled by engine manifold vacuum.
The FPR contains a diaphragm and spring that opens and closes a check ball opening to the fuel return passage. Fuel pressure will be relieved to the fuel tank at 44 psi with no vacuum applied to the FPR. When the engine is operating, manifold vacuum performs in an inverse relationship to fuel pressure. That is, as vacuum increases, (pulling the diaphragm against spring tension), fuel pressure decreases as more fuel is relieved to the tank. As throttle valve opening approaches wide open throttle (WOT), manifold vacuum decreases toward zero in.Hg and the spring in the FPR blocks off more of the fuel return circuit, thus raising the fuel pressure. This enables the engine to receive additional fuel volume as required by high speed/load driving conditions.
FUEL RAIL
Removing Fuel Rail:
The fuel rail is a steel tube with threaded fittings, located on top of the engine and forms the connection between the fuel supply/return hoses, the Fuel Pressure Regulator and the Fuel Injectors. The fuel rail serves to deliver fuel to the injectors and helps stabilize fuel pressure at the injectors.