Fuel Pressure Regulator
Fuel pressure regulator governs flow of fuel to injectors. Pressure varies depending on different vehicle speed and load conditions. To improve hot restart on some models, ECM controls fuel pressure regulator Vacuum Switching Valve (VSV) to change vacuum supplied to pressure regulator. See Fig 1 .
Fuel pressure regulator consists of a fuel chamber and a vacuum chamber separated by a diaphragm. See Fig 2 . Fuel chamber has a fuel inlet pipe and a fuel outlet pipe. Fuel inlet pipe delivers fuel from fuel distributor pipe. Appropriate amount of fuel is then delivered to fuel injector. Excess fuel is returned to fuel tank by fuel outlet pipe.
Vacuum chamber is connected to intake manifold by a hose. Any change in fuel pump delivery pressure or intake manifold pressure will cause diaphragm to move. This movement will maintain pressure balance between intake manifold and fuel chamber to ensure a steady supply of fuel to fuel injectors.