420SEL (126.035) V8-4.2L (116.965) (1986)
Electro-Hydraulic Actuator: Description and Operation
Fuel Distributor with Electro-Hydraulic Actuator
The electro-hydraulic actuator (EHA) replaces the warm up regulator and the frequency valve found on CIS Lambda systems. It is known also as a
differential pressure regulator. The EHA Fig. 12, 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 and the actuator, and therefore, an air/fuel mixture
change.
The signal controlling the EHA comes from the ECU, based on the signals from the various sensors (temp, engine speed, etc.). With the engine
running, a constant system pressure of approx. 5.5 bar (78 psi) is supplied at the fuel inlet. The EHA is adjusted by variations of current thereby
determining the fuel flow rate. The corresponding pressure change in the lower chamber causes movement of the diaphragm, and influences the fuel
volume flowing to the injectors.