Fuel Pressure Regulator: Description and Operation

Fuel Pressure Regulator:

PURPOSE
The pressure regulator maintains constant fuel pressure at the injector nozzles.

CONSTRUCTION
The regulator is a diaphragm-controlled overflow type, which maintains the fuel pressure at a constant 380 kPa (55 psi) above the pressure in the intake manifold. It consists of a metal housing divided into two chambers by a diaphragm: a spring chamber for the pre-stressed helical spring which rests on the diaphragm and a chamber for the fuel.

OPERATION
The fuel pump is capable of high volume output. When the system pressure is exceeded (approx. 55 psi.), 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.

When the engine is turned "OFF", the pressure regulator will temporarily maintain a rest pressure of 280 - 380 kPa (40 - 55 psi).