Fuel Pressure Regulator

The fuel pressure regulator contains a pressure chamber separated by a diaphragm relief valve assembly with a calibrated spring in the vacuum chamber side. Fuel pressure is regulated when pump pressure acting on the bottom side of the diaphragm overcomes the force of the spring action on the top side.

The diaphragm relief valve moves, opening or closing an orifice in the fuel chamber to control the amount of fuel returned to the fuel tank. The fuel pressure regulator maintains a constant 43.5 psi (3.0 kg/cm² ) pressure across the fuel injectors at all manifold depressions.

Vacuum acting on the top side of the diaphragm along with spring pressure controls the fuel pressure. An increase in vacuum creates a decrease in fuel pressure. Under heavy load conditions, the engine requires more fuel flow. Vacuum decreases under heavy load conditions because of throttle opening. A decrease in vacuum allows more pressure to the top side of the pressure relief valve, thus increasing fuel pressure. See Fig 1 .

NOTE: The SFI turbo engine pulses only 1 injector at a time, thus the fuel pressure drop is small. Therefore, the SFI system does not use a fuel pressure accumulator.

Fig 1: Sectional View of Fuel Pressure Regulator