Fuel Pressure Regulator: Description and Operation

Fuel Delivery Components:

The fuel pressure regulator, located on the rear of the right side valve cover along with the pulsation damper, regulates the fuel pressure so that the difference between intake manifold absolute pressure and fuel system pressure is constant.

Injector Duration Vs. Quantity @ Different Manifold Absolute Pressures:

When manifold pressure is low (high vacuum) more fuel will spray from the injectors 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, 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 control vacuum is reduced. More spring pressure is applied to the valve and fuel system pressure is increased by the same amount as manifold absolute pressure, to maintain a constant differential under changing engine loads.

The pressure regulator control (PRC) solenoid, is installed in the vacuum line to the fuel pressure regulator. During hot re-start, the ECU energizes the PRC solenoid valve, which blocks manifold vacuum to the pressure regulator and vents the regulator diaphragm chamber to the atmosphere. With atmospheric pressure at the diaphragm, fuel pressure is increased. Increasing fuel pressure helps reduce fuel percolation due to heat. The PRC solenoid is energized for about 50 seconds after the engine is started. After this time, the PRC solenoid is turned "OFF" and normal vacuum modulation of fuel system pressure is resumed.