Mercedes-Benz OM 651 Service Manual page 22

Piezo injectors
An important component of the new Common Rail
technology are the piezo injectors, which are an
entirely new development. The injector needle is actu-
ated directly by a piezo-ceramic actuator, instead of
being moved by a hydraulic support system.
Compared to a conventional fuel injector, the piezo
injector injects fuel into the combustion chamber
more rapidly, with better atomization and with greater
precision.
A special feature of this system is that the piezo injec-
tors open upon a voltage rise and not upon a voltage
drop.
a Warning
Due to the risk of engine damage, no
connections on the injection system may be
disconnected while the engine is running.
The injector coupling may not be disconnected
and switched to ground while the engine is
running because this would trigger an injection.
– This printout will not be recorded by the update service. Status: 09 / 2008 –
Introduction of New Generation of 4-Cylinder Inline Engines, OM 651
Common rail injection
Piezo injector
a Warning! Risk of death!
During engine operation, a high voltage of up to
250 V is applied to the piezo injectors.
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