Group 30: Electrical system Component description
17
Magnetically controlled propor-
tional valve (MPROP)
A magnetically controlled proportional valve (MPROP)
controls the high pressure pump to ensure that the
correct fuel pressure (rail pressure) is retained despite
varying engine speed and loading.
The input signal to the valve is a PWM signal whose
pulse width is controlled by the engine control module.
When the current through the valve is changed, this af-
fects the fuel flow, which results in changed rail pres-
sure.
Water in fuel switch, secondary
fuel filter
A switch is located in the water trap under the fuel fil-
ter. Its task is to detect whether there is water in the
fuel.
The switch senses the resistance between two pins,
wich are in contact with the fuel. When there is no wa-
ter in the fuel, the resistance is very high. If there is
any water in the fuel, the resistance falls.
Switch, coolant level
The task of the switch is to discover whether the cool-
ant level in the engine (expansion tank) has become
too low. An alarm signal is sent when the coolant level
is too low.
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