300SL (129.061) L6-3.0L (104.981) (1991)
Fuel Pressure Regulator: Description and Operation
Fig. 13 Fuel Pressure Regulator
The fuel-pressure regulator maintains fuel supply pressure to the fuel distributor and injection valves.
The control pressure must be held constant, even when fuel delivery from the supply pump, and injected fuel quantity, vary considerably. This is due to
the fact that any variation of the control pressure has a direct effect upon the air-fuel ratio.
Fuel enters on the left; on the right is the return fuel connection from the fuel distributor. The return line to the tank is connected at the top. When the
fuel pump starts, fuel pressure forces the control diaphragm downward. The pressure of the counterspring forces the valve body to follow the diaphragm
until, after a short distance, it comes up against a stop and the pressure-control function begins.
Typical Fuel System Diagram