Fuel Pressure Regulator: Description and Operation

Fuel Pressure Regulator And Vacuum Control Hose:

Purpose
The fuel pressure regulator maintains a constant pressure difference between the fuel pressure at the injector nozzles and the absolute air pressure (manifold vacuum) in the intake manifold. The ECM, during its fuel metering calculations, relies on the pressure differential remaining constant.

Location
The fuel pressure regulator is mounted on the fuel rail.

Fuel Pressure Regulator (Cut-Away View):

Operation
Control vacuum is supplied from the intake manifold to the diaphragm which operates a pressure valve. When the engine is under very light load, the control vacuum is high, spring pressure against the regulator valve is reduced, and the fuel system is regulated at a lower pressure. When the engine is under heavy load (as in wide open throttle operation), manifold absolute pressure increases and the control vacuum is low. More spring pressure is applied to the valve and fuel system pressure is increased by the same amount as the manifold absolute pressure, to maintain a constant pressure differential.