Injection With A Pressure Booster (4); Graphic Presentation Of The Injection Process - Mercedes-Benz OM 471 Introduction Into Service Manual

System components
The cylinder 1 pressure booster solenoid valve (Y608 y1) is not
actuated.
The fuel lies at rail pressure above and below the pressure booster
(4). The compressed fuel passes out of the rail to the nozzle needle
(7) via the check valve (8) in the pressure booster (4).
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).
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Injection with a pressure booster (4)

i The following descriptions of the variants for injection with a
pressure booster (4) is described using the cylinder 1 fuel injector
(Y608) as an example and can be applied to all other fuel injectors.
Schematic diagram of injection with a pressure booster (4),
shown on cylinder 1 fuel injector (Y608)
3 High pressure feed
4 Pressure booster
6 Spring
7 Nozzle needle
8 Check valve
9 Return spring
10 Fuel return for pressure booster
11 Fuel return for nozzle needle
Y608 Cylinder 1 fuel injector
Y608 y1 Cylinder 1 pressure booster solenoid valve
Y608 y2 Cylinder 1 nozzle needle solenoid valve

Graphic presentation of the injection process

A Actuation of the solenoid valve for the pressure booster before actuation of the nozzle
needle solenoid valve
B Actuation of the solenoid valve for the pressure booster parallel to actuation of the
nozzle needle solenoid valve
C Actuation of the solenoid valve for the pressure booster after actuation of the nozzle
needle solenoid valve
p Injection pressure
t Time
During injection with a pressure booster (4), the injection process
is determined by temporally offset or simultaneous actuation of
the nozzle needle solenoid valve and the solenoid valve for the
pressure booster for the injection process. The following options
for the injection process are possible:
f Actuation of the solenoid valve for the pressure booster
before actuation of the nozzle needle solenoid valve (A)
f Actuation of the solenoid valve for the pressure booster
parallel to actuation of the nozzle needle solenoid valve (B)
f Actuation of the solenoid valve for the pressure booster
after actuation of the nozzle needle solenoid valve (C)
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The nozzle needle (7) is lifted with the aid of the adjacent rail
pressure. The fuel is injected at the specified rail pressure into
cylinder 1.
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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