Fuel Pressure Regulator
The fuel pressure regulator is a vacuum operated diaphragm relief valve mounted at one end of the fuel rail. See Fig 1 . The diaphragm has fuel pressure on one side and regulator spring pressure and intake manifold vacuum on the other side. The fuel pressure regulator maintains a constant pressure differential across the fuel injectors at all times. The pressure regulator compensates for engine load by increasing fuel pressure as the engine vacuum drops.