Fuel Pressure Regulator

Fuel is delivered to the injectors from the in-tank electric fuel pump. Fuel pressure at the injector is controlled by the fuel pressure regulator, located in the fuel line between the injectors and the fuel tank. The pressure regulator is a sealed unit which is divided by a diaphragm into 2 chambers (fuel and spring). The fuel chamber receives fuel through the inlet side from the injector fuel rail. The spring chamber is connected to intake manifold vacuum.

A vacuum-operated diaphragm inside the regulator controls fuel pressure within a specific range, taking into consideration changes in engine load. At idle, intake manifold vacuum is high. The diaphragm is pulled down by intake manifold vacuum, allowing excessive fuel to be returned to the fuel tank through an internal return passage in the regulator. As the throttle is depressed, intake manifold vacuum decreases. The regulator spring overcomes manifold vacuum, causing diaphragm to block fuel return passage to fuel tank. This increases fuel pressure for engine load of high speed operation.