Mercedes-Benz OM 651 Service Manual page 24

Injection quantity correction
Injection quantity correction consists of two proce-
dures:
• Main injection quantity correction
• Zero quantity calibration
Main injection quantity correction
With main injection quantity correction, the injected
fuel quantity is corrected using the oxygen sensor
upstream of the catalytic converter. The injection
quantity is changed until the specified lambda value
stored in the CDI control unit is reached.
CDI injection system
1 Fuel heating element
2 Fuel filter housing
3 Rail
– This printout will not be recorded by the update service. Status: 09 / 2008 –
Zero quantity calibration
The friction produced during opening and closing of
the piezo injectors causes wear on the nozzle seat of
the nozzle needle. This causes a change in the injec-
tion quantity over the service live of the injector.
This change in the injection quantity can be corrected
by adjusting the actuation duration (zero quantity cali-
bration). On engines with the Delphi injection system,
correction is performed with the help of two knock
sensors.
4 Rail pressure sensor
5 Pressure line
6 Piezo injector
Introduction of New Generation of 4-Cylinder Inline Engines, OM 651
Common rail injection
7 High-pressure pump
8 Quantity control valve
9 Pressure regulator valve
23
q