Fuel Pressure Regulator

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

A vacuum-operated diaphragm inside regulator maintains fuel pressure at a specific range, taking into consideration changes in engine load. At idle, intake manifold vacuum is high, causing diaphragm to be pulled down, allowing excessive fuel to be returned to fuel tank. As throttle is depressed, intake manifold vacuum decreases, allowing diaphragm regulator spring to overcome manifold vacuum, causing diaphragm to block fuel returning to fuel tank. This causes an increase in fuel pressure.