Fiat 1998 Marea Weekend, Service Manual

Page: 312 / 846

Engine
Fuel system
Marea- Marea Weekend ft
99 update
10.
FUEL
ANTI-EVAPORATION SYSTEM
The anti-evaporation system is designed to prevent the fuel vapours, composed of the lightest fractions of
hydrocarbons which basically form in the tank, from being discharged into the atmosphere.
The system consists of the tank, the vapour separator, two float valves, a two-way ventilation valve, the
charcoal filter and a charcoal filter solenoid valve controlled by the control unit. The cap contains a two-
way safety valve.
Operating principle
The system operates, above all, at high outside temperatures when the temperature of the fuel increases
and, consequently, the tendency to evaporation increases: in this situation there is an increase in pressure
inside the tank.
In particular, even when, the tank (1) is full, the two float valves (3) remain open, as they are located
higher than the breather pipe and therefore always allow the fuel vapours to reach the separator (2),
thereby preventing fuel from escaping.
The fuel vapours reach the charcoal filter (6) when the pressure inside the tank causes the opening of the
ventilation valve (8). This valves also allows an intake of air into the tank through the charcoal filter, if
necessary, when the level of the fuel decreases.
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 scavening of the charcoal filter.
If, as a result of a malfunction with any 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 lev-
els from becoming excessive.
1. Fuel tank
2. Vapour separator
3. Float valve
4. Cap with safety valve
5. Engine management control unit
6. Charcoal filter
7. Charcoal filter solenoid valve
8. Safety and ventilation valve
9. Inlet manifold
10. System relay
4 2
Print n° 506.763/15