Differential Pressure Regulator: Description and Operation

Fig. 18 Fuel Distributor with Differential Pressure Regulator:

The differential pressure regulator replaces the warm up regulator and the frequency valve found on CIS Lambda systems. The pressure regulator Fig. 18, is mounted on the fuel distributor. It acts as a pressure regulator which operates as a plate valve. The position of the plate can be varied causing a differential pressure change between the lower chamber of the fuel distributor and the actuator, and therefore, a mixture change.
The signal controlling the pressure regulator comes from the ECU, based on the signals from the various sensors (temp, engine speed, oxygen sensor, etc.). The operating range is from -50 to +150 mA.
With the engine running, a constant system pressure of 5.2 - 5.6 bar (75 - 82 psi) is supplied at the fuel inlet. The pressure regulator is adjusted by variations of current thereby determining the control pressure to the fuel distributor control plunger. The differential pressure can be adjusted from 0 to 1.6 bar (24 psi) below system pressure. The corresponding pressure change in the lower chamber causes movement of the diaphragm, and influences the fuel volume flowing to the injectors.
The differential pressure regulator is constructed so that a malfunction causes a power loss, the plate inside the valve would deflect enough under system pressure to maintain a differential pressure of about 0.4 bar (5.8 psi). This combined with the 0.2 bar (3 psi) difference caused by the system pressure regulator result in a difference of 0.2 bar between the upper and lower chambers in the fuel distributor. In this condition the car will still be driveable, but will run roughly due to a lean air/fuel ratio.