Fuel Pressure Regulator

The pressure regulator is a sealed unit which is divided by a diaphragm into 2 chambers (fuel and spring chambers). The fuel chamber receives fuel through both sides from the injector fuel rail. The spring chamber is connected to intake manifold vacuum.

At idle, when fuel requirements are low, the diaphragm is pulled down by intake manifold vacuum to allow excessive fuel to return to the fuel tank. As the throttle is depressed and fuel requirements increase, intake manifold vacuum decreases and diaphragm moves up shutting off the fuel return line to maintain constant fuel pressure.