Fuel pressure regulator (Peugeot Eurovans 806)

The fuel pressure regulator constantly maintains fuel pressure in the fuel line at 3.0 bar. The fuel pressure regulator is installed on the fuel line and consists of two chambers separated by a diaphragm. The upper chamber has a spring that forces pressure into the lower chamber and closes the outlet diaphragm. The pressurized fuel stream flows into the lower chamber, which forces pressure onto the diaphragm. When the pressure begins to exceed 3.0 bar, the outlet diaphragm opens and excess fuel returns to the fuel tank through the return line.

A vacuum hose connects the upper chamber to the intake manifold so that changes in intake manifold pressure do not affect the amount of fuel injected. This means that the pressure in the fuel line is always a constant pressure, which is higher than the pressure in the intake manifold. The amount of fuel injected thus depends solely on the injector opening time, which is determined by the electronic control unit, and not on changes in fuel pressure.

At idle, with the vacuum line disconnected or the engine stopped and the pump running, or the throttle wide open, the fuel pressure in the system will be approximately 3.0 bar. At idle (the vacuum tube is connected) the fuel pressure will be approximately 0.5 bar when the system is pressurized.

Material copied from the resource: PEUGEOTBOOK