Mercedes-Benz OM 471 Introduction Into Service Manual page 176

Actuation of the solenoid valve for the pressure booster before
actuation of the nozzle needle solenoid valve (A)
The cylinder 1 pressure intensifier solenoid valve (Y608 y1) is
actuated before the cylinder 1 nozzle needle solenoid valve (Y608
y2) by the engine management (MCM) control unit (A4). The rail
pressure applied below the pressure booster (4) is reduced via the
fuel return pressure booster (10).
The pre>compressed fuel from the rail which is also pressing
against the nozzle needle (7) is compressed by the pressure
booster (4) up to a high fuel pressure level (red).
If the engine management (MCM) control unit (A4) actuates the
cylinder 1 nozzle needle solenoid valve (Y608 y2) then the fuel
pressure in the control space is built up above the nozzle needle
(7) via the fuel return nozzle needle (11). The nozzle needle (7) is
lifted with the aid of the fuel pressure.
The fuel is injected with a fuel pressure increased by the pressure
booster (4) into cylinder 1.
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Actuation of the solenoid valve for the pressure booster parallel
to actuation of the nozzle needle solenoid valve (B)
The cylinder 1 pressure intensifier solenoid valve (Y608 y1) and the
cylinder 1 nozzle needle solenoid valve (Y608 y2) are actuated
simultaneously by the engine management (MCM) control unit
(A4).
The rail pressure applied below the pressure booster (4) is reduced
via the fuel return pressure booster (10).
The fuel pressure in the control space above the injector needle
(7) is reduced via the fuel return injector needle (11).
The nozzle needle (7) is lifted at first with the aid of the adjacent
rail pressure.
During injection the pre>compressed fuel from the rail is
compressed by the pressure booster (4) to a high fuel pressure
level (red).
The fuel pressure increases during injection.
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Actuation of the solenoid valve for the pressure booster after
actuation of the nozzle needle solenoid valve (C)
The fuel pressure in the control compartment above the nozzle
needle (7) is initially reduced. This occurs in that the engine
management (MCM) control unit (A4) actuates the cylinder 1
nozzle needle solenoid valve (Y608 y2). The nozzle needle (7) is
lifted with the aid of the adjacent rail pressure. The fuel is injected
at the prescribed rail pressure.
After beginning the injection the cylinder 1 pressure booster
solenoid valve (Y608 y1) is actuated and the rail pressure applied
under the pressure booster (4) reduces over the fuel return
pressure booster (10).
On then is the pre>compressed fuel from the rail compressed by
the pressure booster (4) to a high fuel pressure level (red).
This means that the fuel pressure only increases some time after
beginning injection.
i Introduction of engine OM 471 and exhaust aftertreatment > 09/2011 >
– This printout will not be recorded by the update service. Status: 09 / 2011 –
System components
The level of the fuel pressure is dependent on the point in time of
the initial actuation of the cylinder 1 pressure booster solenoid
valve (Y608 y1).
If the engine management (MCM) control unit (A4) interrupts
actuation of the cylinder 1 pressure booster solenoid valve
(Y608 y1), the pressure below the pressure booster (4) builds up
again. The pressure booster (4) goes back into its starting position.
If the engine management (MCM) control unit (A4) interrupts
actuation of the cylinder 1 nozzle needle solenoid valve
(Y608 y2) the pressure in the control space above the nozzle
needle (7) builds up again. The nozzle needle (7) is pressed onto
its seat again with the aid of the spring (6) and the injection
process stops.
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If the engine management (MCM) control unit (A4) interrupts
actuation of the cylinder 1 pressure booster solenoid valve
(Y608 y1), the pressure below the pressure booster (4) builds up
again. The pressure booster (4) goes back into its starting position.
If the engine management (MCM) control unit (A4) interrupts
actuation of the cylinder 1 nozzle needle solenoid valve
(Y608 y1) the pressure in the control space above the nozzle
needle (7) builds up again. The nozzle needle (7) is pressed onto
its seat again with the aid of the spring (6) and the injection
process stops.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
If the engine management (MCM) control unit (A4) interrupts
actuation of the cylinder 1 pressure booster solenoid valve
(Y608 y1), the pressure below the pressure booster (4) builds up
again. The pressure booster (4) goes back into its starting position.
If the engine management (MCM) control unit (A4) interrupts
actuation of the cylinder 1 nozzle needle solenoid valve
(Y608 y1) the pressure in the control space above the nozzle
needle (7) builds up again. The nozzle needle (7) is pressed onto
its seat again with the aid of the spring (6) and the injection
process stops.
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