Fuel Pressure Regulator: Description and Operation

Fig. 4 Fuel pressure regulator:

The pressure regulator is a diaphragm type relief valve with injector pressure acting on one side of the diaphragm and manifold and spring pressure acting on the other, Fig. 4. The regulator maintains constant pressure in the fuel rail by controlling flow in the return line. The pressure regulator also serves as a load compensator by increasing fuel pressure at times of low manifold vacuum.