Fuel High Pressure Circuit Function - Mercedes-Benz OM 471 Introduction Into Service Manual

Functions
GF47.00>W>3013H
ENGINES 471.9 in MODEL 963
Code (M5Z) Engine version Euro VI shown
1 Fuel system high pressure pump
2 Fuel high>pressure lines
(from fuel system high pressure
pump to rail)
3 Rail
4 Fuel high>pressure lines
(from rail to respective fuel injector)
5 Pressure limiting valve
6 Fuel return lines of fuel injectors
7 Fuel return line from pressure
limiting valve
A4 Engine management control unit
(MCM)
B622 Rail pressure sensor
Y608 Cylinder 1 fuel injector
Y609 Cylinder 2 fuel injector
Y610 Cylinder 3 fuel injector
Y611 Cylinder 4 fuel injector
Y612 Cylinder 5 fuel injector
Y613 Cylinder 6 fuel injector
Y642 Quantity control valve
C Fuel high pressure lines
D Fuel return lines
The fuel delivered by the fuel pump and cleaned by the fuel filter
module flows via the quantity control valve (Y642) to the fuel
high pressure pump (1).
Depending on the operating status of the engine, the engine
management control unit (MCM) (A4) uses the quantity control
valve (Y642) to determine the amount of fuel that is led into the
fuel system high pressure pump (1).
The fuel is compressed by the fuel high pressure pump (1) and
delivered to the rail via the two fuel high pressure lines (2). The
fuel pressure of about 900 bar that is generated in this way is
detected via the rail pressure sensor (B622) and passed on to the
engine management (MCM) control unit (A4).
If the maximum permissible rail pressure has been exceeded, the
mechanical pressure limiting valve (5) opens and the excess fuel
flows back from the pressure limiting valve (7) to the fuel filter
module in the low>pressure fuel circuit via the fuel return line.
Engine management control unit (MCM),
component description
Component description for rail pressure
sensor
Component description for fuel injectors
Component description for quantity
control valve
Component description for fuel system
high pressure pump
Pressure limiting valve, component
description
100

Fuel high pressure circuit function

– This printout will not be recorded by the update service. Status: 09 / 2011 –
The highly compressed fuel passes from the rail (3) to the fuel
injectors for cylinder 1 to 6 (Y608 to Y613) via the fuel high
pressure lines (4).
From fuel injectors for cylinders 1 to 6 (Y608 to Y613) the fuel is
injected, according to the injection variant, with or without
additional pressure amplification into the respective cylinder. The
injection pressure can be up to 2100 bar.
The injection quantity, the injection timing point and the relevant
injection variants are determined by the engine management
(MCM) control unit (A4) depending on the operating condition of
the engine.
The diverted quantity of the solenoid valves at the nozzle needles
and the diverted quantity of the solenoid valves at the pressure
boosters pass via the two fuel return lines of the fuel injectors (6)
back to the fuel filter module and therefore back into the low>
pressure fuel circuit.
A4
B622
Y608. to Y613
Y642
20.7.11
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