57
Electrical circuit
SSP207/83
F88
J220
1
2
The pressure switch for power steering is
located on the vane pump. It informs the
engine control unit when the vane pump is
subjected to a load.
The vane pump is driven by the engine by
means of a the ribbed V-belt. At full steering
lock, the vane pump generates a pressure.
This also places a higher load on the engine,
and idling speed can drop sharply. The signal
which the pressure switch generates enables
the engine control unit to recognise engine
loading in time and to regulate engine torque
at idling speed.
The ME 7.5 determines itself how engine tor-
que is to be increased at idling speed, in order
to counteract the load (e.g. ignition angle cor-
rection towards “retard“).
Pressure switch for power steering
This is how it works:
As steering forces increase, the pressure
switch closes and sends a signal to the engine
control unit.
Without steering wheel movement, the pull-
up integrated in the engine control unit is at
+5 V.
When the pressure switch is closed, the
engine is connected to earth.
Components
J220
Engine control unit
F88
Pressure switch for power steering
SSP207/113
