Fiat 1998 Marea Weekend, Service Manual

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Engine
Fuel system
Marea- Marea Weekend ft
99 range
10.
ANTI-EVAPORATION SYSTEM COMPONENTS
Multi-purpose valve
This valve is used to carry out various functions, namely:
- preventing the flow of liquid fuel, if the tank is too full or if there is an accident during which the vehicle
overturns.
- allowing the breathing of fuel vapours toward the active charcoal filter;
- allowing the ventilation of the tank if there is a vacuum in it.
The valve consists of a float casing (2), a heavy ball (3), a plate thrust against the valve body by the
spring (5) and a plate (8) thrust against the plate (4) by the spring (9). The operation of the multi-
purpose valve can be summarized in the following cases, depending on how full the fuel tank is:
a. if the tank is full, the float (2) shutters the port (1) preventing the liquid fuel from reaching the active
charcoal filter thereby avoiding damaging it;
b. if the level of the fuel in the tank decreases, the float (2) descends and rests on the ball (3), opening
the port (1); when the pressure exerted by the fuel vapours on the plate (4) exceeds the loading of the
spring (5), a ring section opens between the actual plate and the valve body, which allows the fuel va-
pours to flow out from the duct (6) and reach the active charcoal filter;
a. if the level of the fuel in the tank decreases to the extent that a vacuum is produced inside the tank,
this vacuum acts on the plate (8) and, overcoming the spring (9) loading, recalls it downwards, al-
lowing the ventilation of the tank through the port (7).
b. if the vehicle overturns, irrespective of how full the tank is, the ball (3), weighing on the float (2),
pushes it against the port (1) preventing the dangerous escape of fuel and the consequent risk of fire.
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