Diaphragm Pressure Regulator Function

Full throttle
At full throttle, no vacuum is active in the spring chamber (9) which is separated from the fuel chamber (8) by a diaphragm (5). If the set pressure is exceeded, the diaphragm (5) is pushed against the compression spring (6). The valve (3) attached to the diaphragm opens the return flow (2) and the excess fuel flows back pressureless to the fuel tank.







Idle speed, part throttle
The spring chamber (9) is connected by a suction pipe connection (7) to the intake manifold. The vacuum of the intake manifold acts through the diaphragm to counter the force of the spring (6), as a result of which the fuel pressure is reduced by the momentary intake manifold vacuum. This ensures that the fuel pressure in the fuel rail is dependent on the intake manifold pressure and the pressure drop through the fuel injection valves is the same at all positions of the throttle valve.
Consequently, the fuel quantity ejected is dependent solely on the opening time of the fuel injection valves.






Fuel pressure diaphragm