Fuel Pressure Regulator
The fuel pressure regulator is attached to the throttle body. See Figure and Fig 1 . The regulator is adjustable and controls the amount of pressure in the fuel system. As fuel from the fuel pump enters the top of the regulator, the relief valve and regulator spring are forced down opening a passage to the fuel return tube, allowing a certain amount of fuel to return to the fuel tank. A pivot on top of the diaphragm keeps the diaphragm from tipping to one side.
The amount of pressure to force the regulator spring down determines fuel system pressure. Fuel system pressure is controlled by the adjusting screw located at the bottom of the regulator housing. Turning the screw inward increases fuel pressure. Turning the screw outward decreases fuel pressure.