Detonation Sensors (0.261.231.131) - Fiat Bravo Service Manual

Engine
Fuel system
10.
When measuring the distance, it is vital
to be at right angles to the flywheel
and corresponding to a tooth and not a
gap.
24
Checking the gap
The rpm and TDC sensor is fixed directly to
the cylinder block/crankcase and therefore
the gap and the angular position do not need
adjusting. If a fault is suspected, the gap can
be checked as follows:
- remove the rpm and TDC sensor;
- check that the distance between the sur-
face of the sensor and the flywheel t o o t h
corresponds to the total length of the sen-
sor probe (34.5mm) w i t h the gap (0.8 - 1 . 5
m m ) .
D E T O N A T I O N S E N S O R S (0.261.231.131)
The detonation sensors are located in the
monobloc under the inlet manifolds and be-
tween cylinders 1 -2 and 4 - 5 , respectively.
These sensors have a bush to prevent inap-
propriate torque tightening.
If they are replaced, do not place w a s h e r s
or shims between the
/crankcase and sensor contact surfaces.
When the engine is knocking (detonation),
vibrations of a certain frequency are pro-
duced in the cylinder block/crankcase.
This phenomenon produces a mechanical
ripercussion on a piezoelectric crystal w h i c h
sends a signal to the control unit w h i c h , on
the basis of this signal, reduces the ignition
advance (by 3° up to a maximum of 9.7°) u n -
til the phenomenon disappears. Later, the
advance is gradually restored to the basic val-
ue.
Wiring connector
The sensors are connected to the electronic
control unit (Pins M 2 2 / M 5 4 and M 3 8 / M 6 )
by twisted cables covered in an anti-interfer-
ence outer casing.
The numbers indicate
control unit pins.
Bravo ft 20v
98 range
cylinder block-
the corresponding
Print no. 506.670/16