Fiat 1998 Marea Weekend, Service Manual

Page: 295 / 846

Marea- Marea Weekend ft
99 update
3N27GJ02
1. Deflector
2. Mangetic material
3. Gap
Wiring connector
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H
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- 31A
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22A
Engine
Fuel system
10.
ENGINE TIMING SENSOR
The engine timing signal, in conjunction with
the engine rpm and TDC signal, allows the
control unit to recognize the succession of
cylinders to implement the phased injection.
This signal is produced by a Hall effect sensor,
fitted by the exhaust camshaft drive pulley.
NOTE It is not possible to carry out any ad-
justments to the angular position of the
sensor.
Operating principle
A semi-conductor layer, through which the
current passes, immersed in a normal magnetic
field (lines of force perpendicular to the direc-
tion of the current) produces a difference in
power, known as Hall voltage.
If the intensity of the current remains constant,
then the voltage produced only depends on
the intensity of the magnetic field. It is there-
fore simply necessary to alter the intensity of
the field perodically in order to produce a
modulated electrical signal.
In practice, to achieve this change, the sensor
passes through a metal ring (fixed to the inner
part of the timing pulley) which has a series of
openings: as it moves, when the ring covers
the sensor it blocks the magnetic field and the
signal remains low, whilst corresponding to the
openings, the field is enclosed and the signal
becomes high
The alternating of the signals therefore de-
pends on the succession of the openings (see
chapter on "signal management").
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