Fuel Pressure Regulator: Description and Operation

Fuel Pressure Regulator:

The pressure regulator controls the pressure in the fuel system. The pressure regulator is fitted at the end of the down stream side of the fuel injector rail. The pressure regulator is a diaphragm-controlled overflow type which maintains the fuel pressure at approx. 3 bar. It consists of a metal housing divided into two chambers by a beaded diaphragm: a spring chamber for the pre-stressed helical spring which rests on the diaphragm and a chamber for the fuel.
When the set pressure is exceeded, a valve controlled by the diaphragm opens the inlet to an overflow channel through which the excess fuel can flow back to the fuel tank without pressure. The spring chamber of the pressure regulator is connected by a vacuum line to the intake manifold behind the throttle valve. This results in the fuel system pressure being dependent on the absolute pressure in the intake manifold and the pressure drop across the injection valves therefore being identical for every throttle-valve position.