Fiat Bravo Service Manual page 252

Engine Bravo-Brava © i ^
Fuel system
10.
Operating principle
The anti-evaporation system has the aim of preventing the fuel vapours, made up of the lightest parts of
the hydrocarbons which basically 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 increses
and consequently the tendency towards evaporation increases: in this situation there is an increase in
the pressure inside the tank.
In particular, even with the tank (1) full, with the vehicle stationary the two float valves (3) remain open
as they are located higher than the breather pipe and therefore they allow the vapours to reach the sepa­
rator (2) from where they mainly return to the tank as they condense.
If, on the other hand, there is strong splashing when the vehicle is driving or it overturns, the valves (3)
close preventing fuel from escaping.
When the pressure inside the tank reaches about 30-40 mbar, the multi-purpose valve (8) opens and the
fuel vapours reach the charcoal filter (6). The valve (8) also allows an intake of air into the tank through
the charcoal filter if necessary following the lowering of the level of fuel and the consequent vacuum
which is created inside the tank.
When the engine is running, the control unit operates the charcoal filter solenoid valve which allows the
intake of vapours by the engine and the consequent scavenging of the charcoal filter.
If as a result of the malfunction of one of the components, the pressure inside the tank increases to dan­
gerous levels, the safety valve located in the cap (4) allows the pressure to be discharged outwards. If
necessary, this valve can open in the opposite direction, to ventilate the tank and prevent the vacuum
reaching excessive values.
P4A42BJ01
1. Fuel tank 6. Charcoal filter
2. Vapour separator 7. Charcoal filter solenoid valve
3. Float valve 8. Multi-purpose valve
4. Cap with safety valve 9. Inlet manifold
5. Engine control unit 10. Relay
42 Printho.506.670