Fuel Pressure Regulator: Description and Operation

Pressure Regulator

The pressure regulator is mounted on the short side of the fuel rail.

The pressure regulator maintains a constant ratio between the fuel pressure and the pressure in the intake manifold. This ensures that the amount of fuel injected is determined exclusively by the opening duration of the electromagnetic injectors.

The pressure regulator is a diaphragm-controlled overflow valve set for 3.0 bar. The regulator consists of a metal housing divided into two chambers by a press-fitted diaphragm. In one of the chambers a spiral spring presses against the diaphragm while fuel flows through the other chamber.

When the preset pressure is exceeded a valve controlled by the diaphragm exposes an opening to the return line through which superfluous fuel can flow back to the fuel tank.

The spring-loaded chamber of the pressure regulator is connected by a hose to the engine's intake manifold after the throttle. In consequence, the pressure in the fuel system is affected by the absolute pressure in the intake manifold, with the result that the pressure drop across the injectors is constant at all intake manifold pressures.