Mercedes-Benz OM 651 Service Manual page 17

Crankshaft assembly
Camshafts
The gear drive drives the camshaft sprockets and the
connected camshafts via a timing chain. The mainte-
nance free timing chain is tried and tested and has
proven longevity. The cams are fixed to the camshaft
by means of internal high-pressure forming (IHU).
Camshaft sprocket
The camshaft sprocket is connected to the camshaft
by a center bolt. The center bolt of the camshaft has a
left-hand thread.
Exhaust camshaft with sensor wheel
1 Drive gear
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Introduction of New Generation of 4-Cylinder Inline Engines, OM 651
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2 Exhaust camshaft
– This printout will not be recorded by the update service. Status: 09 / 2008 –
Sensor wheel
The sensor wheel is fixed to the exhaust camshaft. In
combination with the Hall sensor, the sensor wheel
makes it possible to determine the camshaft position
and rpm.
The Hall sensor generates a magnetic field through a
built-in permanent magnet. The magnetic field is peri-
odically interrupted by an orifice plate on the sensor
wheel while the engine is running. The signal which
this generates is used by the CDI control unit and
serves as a substitute signal for emergency engine
operation if the position sensor for the crankshaft
fails.
3 Sensor wheel with orifice plate