Determination Of The Compression Stroke At Cylinder 1, Function - Mercedes-Benz OM 471 Introduction Into Service Manual

Functions
GF07.00>W>3002H
ENGINE 471.9 in MODEL 963
1 Flywheel
2 Camshaft sprocket
3 Groove (to detect the crankshaft angle for failure of the
crankshaft position sensor)
4 Additional groove (for detecting the compression cycle at
cylinder 1)
A4 Engine management control unit (MCM)
B600 Crankshaft position sensor
B601 Camshaft position sensor
General information
Detection of the compression cycle at cylinder 1 takes place as
soon as the engine has started. Because the position of the
crankshaft alone is not enough, the engine management (MCM)
control unit (A4) also uses the signals from the camshaft position
sensor (B601).
If the compression cycle at cylinder 1 is, however, just known the
one time then all further compression cycles are just calculated
based on signals from the crankshaft position sensor (B600).
Signals from the camshaft position sensor (B601) are exclusively
used to determine the rotational speed or the compression cycle
at cylinder 1 if the crankshaft position sensor (B600) fails.
The reason for this is that the crankshaft position sensor (B600)
delivers more precise values about the position of the crankshaft
than does the camshaft position sensor (B601); thus start of
actuation of the fuel injectors can be determined that more
exactly.
Component description for engine
management (MCM) control unit
Component description for crankshaft
position sensor
Component description for camshaft
position sensor
54

Determination of the compression stroke at cylinder 1, function

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Function
The camshaft sprocket (2) on the intake camshaft has 12 grooves
(3) which are respectively distributed at a distance of 30∞ from
each other over the whole circumference of the camshaft sprocket
(2), as well as an additional groove (4) before top dead center
(TDC) of cylinder 1.
As soon as the intake camshaft turns, the grooves in the camshaft
position sensor (B601) generate changes in the magnetic field
which are converted by an electronic analysis system into
switching signals and passed on to the engine management
(MCM) control unit (A4).
If the engine is then started, the engine management (MR)
control unit uses the additional groove (4) (A4) to check when
cylinder 1 is in its compression cycle.
The fact that the engine management (MCM) control unit (A4)
determines the position of the crankshaft at the same time via the
crankshaft position sensor (B600) means that it can compare the
position of the additional groove (4) to the position of the gap on
the flywheel, so that signals from the crankshaft position sensor
(B600) are sufficient to determine the compression cycle of
cylinder 1 and thus actuation begin of the fuel injectors.
A4
B600
B601
2.8.11
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