Fuel Pressure Regulator: Description and Operation

Fuel Pressure Regulator:

The fuel pressure regulator, located on the front end of the fuel rail, maintains a constant pressure differential between the fuel pressure and the intake manifold absolute pressure.

Injector Duration Vs. Quantity @ Different Manifold Absolute Pressures:

When the manifold pressure is low (high vacuum) more fuel will spray from the injector than will at high manifold pressure (low vacuum) for the same injection duration and fuel pressure. The fuel pressure regulator increases the fuel system pressure as manifold absolute pressure increases so that the percent change in injection duration equals the percent change in the quantity of fuel injected.

Fuel Pressure Regulator:

Control vacuum is applied to a diaphragm which operates a pressure valve. When the engine is under very light load, the demand for fuel is low and the control vacuum is high (low manifold absolute pressure). 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), The demand for fuel is greater and the control vacuum is low (high manifold absolute pressure). More spring pressure is applied to the valve and fuel system pressure is increased by the same amount as the increase in manifold absolute pressure. Control vacuum is regulated by a computer controlled solenoid valve (PRC solenoid valve) to maintain the correct amount of pressure regulator control vacuum for all engine operating conditions and loads (see Computers and Control Systems). This maintains a constant pressure differential between the fuel system and the intake manifold absolute pressure.