Fiat 1998 Marea Weekend, Service Manual

Page: 337 / 846

Engine
Marea- Marea Weekend
ft
Fuel system 99 range
10.
SYSTEM FOR RECIRCULATING GASES COMING FROM THE CYLINDER BLOCK/CRANKCASE
(BLOW-BY)
This system controls the emission, from the cylinder block/crankcase, of breather gases consisting of
air/petrol mixtures and burnt gases which escape from the piston seals in addition to lubricant oil vapours,
recirculating them to the inlet.
The breather gases, directed by special partitions, rise by the engine oil filler and pass through the coils
(7), under the tappet cover, where they lose part of the oil which they contain which returns to the cam-
shafts, via the pipe (6), in the form of droplets.
The pipe (6) is a siphon shape to avoid the escape of breather gases
and only allow the recirculation of the oil droplets.
With the butterfly open, the gases escape through the outlet (5) and are sent, via the connector (4) on
the air hose, upstream of the butterfly valve, to the manifold.
With the butterfly closed, the vacuum in the inlet manifold draws in the gases through the intake (1) and,
via the pipe (2), they reach the connector (3) on the inlet manifold which contains a PCV valve (8)
(Positive Crank Ventilation) which shutters the intake.
The PCV valve can be modulated and the quantity of gas which passes through is proportional to the
vacuum in the inlet manifold.
When the butterfly valve is completely open (condition A), the vacuum inside the inlet manifold is mini-
mal, the spring (10) is fully extendd and the PCV valve allows the maximum flow of breather gases.
Conversely, with the butterfly completed closed (condition B), the vacuum inside the manifold is maxi-
mum, which causes the movement of the piston (9) which shutters the flow of breather gaess inside the
PCV valve thereby restricting the intake of gases into the manifold.
A
4A12JL01
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Print n° 506.763/14