Fuel Pressure Regulator
The fuel pressure regulator is a diaphragm-operated pressure relief valve consisting of a diaphragm, a spring, and a valve. The fuel pressure regulator keeps the fuel pressure applied to the fuel injector at a pressure much more than the pressure in the intake manifold.
The pressure applied to chamber "A" of the fuel pressure regulator is the intake manifold pressure. The pressure applied to chamber "B" of the fuel pressure regulator is fuel pressure. See Fig 1 . When the fuel pressure rises at least 30 psi (210 kPa) higher than the intake manifold pressure, the fuel pushes a valve in the regulator open and excess fuel returns to the fuel tank via the fuel return pipe.