Fuel Anti-Evaporation Circuit Diagram - Fiat 1998 Marea Service Manual

Marea-Marea
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FUEL ANTI-EVAPORATION CIRCUIT DIAGRAM

1. Fuel vapour cut out solenoid valve
2. Charcoal filter
3. Multi-purpose valve
4 . Fuel vapour separator
The anti-evaporation system is designed to prevent the fuel vapours, which are made up of the lightest
fractions of hydrocarbons which form in the tank, from being discharged into the atmosphere.
The system operates above all at high outside temperatures when the temperature of the fuel increases and
consequently the tendency for evaporation increases; in this situation there is an increase in pressure in-
side the tank (7).
In particular, even when the tank (7) is full, with the vehicle stationary the float valves (6) remain open as
they are higher than the breather pipe and therefore allow the vapours to reach the separator (4), from
where, on condensing, they mainly return to the tank (7).
If, on the other hand, the fuel splashes around whilst driving or the vehicle overturns, the float valves (6)
close preventing the escape of fuel.
When the pressure inside the tank reaches about 30-40 mbar, the multi-purpose valve (3) opens and the
fuel vapours reach the charcoal filter (2). The valve (3) also allows an intake of air into the tank through
the charcoal filter, for example following the lowering of the fuel level with the consequent vacuum which
is created inside the tank.
With the engine running, the control unit (8) operates the fuel vapour cut out solenoid valve (1), which
allows the intake of vapours by the engine and the consequent scavenging of the charcoal filter (2).
If, as the result of the malfunction of one of the components, the pressure inside the tank increases dan-
gerously, the safety valve (5), located near the cap, allows the pressure to be discharged outwards. If nec-
essary, this valve can open in the opposite direction to ventilate the tank and prevent the vacuum reaching
excessive levels.
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5. Safety and ventilation valve
6. Float valve
7. Tank
8 . Injection/ignition control unit
Engine
Fuel system
10.
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