184000292 - 1080E EVAPORATION CONTROL SYSTEM
SPECIFICATIONS
The evaporation control system prevents fuel vapours, i.e. the lighter hydrocarbon fractions that build up mainly in the tank, from escaping into the atmosphere.COMPOSITION
The system consists of a tank, a vapour separator, two float valves, a two way ventilation valve inside the fuel filler cap, a carbon filter and a carbon filter flushing solenoid controlled by the control unit.OPERATION
The system operates mainly at high external temperatures when fuel temperature increases and the tendency to evaporate also increases: pressure rises inside the tank under these circumstances.In particular, even with tank (1) full, the two float valves (3) remain open because they are situated higher than the vent pipe. They therefore always allow fuel vapours to reach separator (2) and prevent fuel from emergingThe fuel vapours reach the charcoal filter (6) via a calibrated port in a valve housed inside the vapour filter/separator assembly. This port also allows the introduction of air into the tank via the charcoal filter if this is necessary following a drop in the fuel level.When the engine is running, the control unit controls the carbon filter flushing solenoid, which allows vapour to be taken in by the engine and thus flushing of the carbon filter.If pressure inside the tank increases to dangerous levels due to component malfunction, the pressure relief valve in cap (4) allows pressure to be vented to the outside. If necessary, this valve can open in the opposite direction to ventilate the tank and prevent the vacuum from reaching excessive levels.
EVAPORATION CONTROL SYSTEM COMPONENTS
FLOAT VALVE
These valves are used for carrying out the following functions:
- preventing the escape of liquid fuel in the case of an accident where the vehicle overturns;
- allowing the breathing of fuel vapours from the tank to the separator and therefore to the activated charcoal filter;
- allowing the ventilation of the tank if there is a vacuum inside.
Tank full
If the tank is full, the float (2) shutters the port (3) preventing the liquid fuel from reaching the separator.
Intermediate fuel level
If the fuel level in the tank decreases, the float (2) descends opening the port (3). This allows the fuel vapours to escape from the tank and reach the separator and the activated charcoal filter, or through the same circuit to ventilate the tank when the pressure inside is below the pressure outside.
Seal in the event of roll-over
If the vehicle overturns, irrespective of how full the tank is, the float (2), weighing down with its own weight and that of the fuel on the port (3), prevents the dangerous flow of fuel to the vapour separator and the consequent risk of the vehicle catching fire.
CANISTER
Specifications
Mounted in the right rear wheelarch, this consists of an activated-charcoal filter element (1) which absorbs the fuel vapours coming from the separator (2) housed in the actual assembly.The fuel vapours flow through a calibrated port (3) in the valve at the top of the separator.A one-way valve (4) allows the entry of external (scavenging) air which comes into contact with the carbon granules, removing the petrol vapours and directing them through the outlet (5) to the inlet manifold when the fuel vapour solenoid valve is open.
Fuel vapour solenoid
Specifications
This is directly on the modular inlet manifold, and is controlled by the fuel injection control unit.The function of the solenoid is to allow fuel vapours stored in the engine intake canister through to the engine intake.If there is no supply the solenoid valve is in the closed position, preventing the fuel vapours from enriching the mixture too much.Operation
The solenoid valve is operated by the control unit according to a specific strategy (see 1056)When energized, the electromagnet (1) attracts the shutter (2), which overcomes the load of the flat spring (3) and closes the hole (4), preventing the passage of fuel vapours.
SAFETY AND VENTILATION VALVE
Operation
This valve is built into the fuel filler cap, and it carries out the following functions, depending on the pressure present in the tank:
- it discharges to the outside any surplus pressure which is created inside the tank (safety function); the pressure acts on the plate (2) and, overcoming the load of the spring (1), allows the surplus vapours to be discharged to the outside.
- it allows external air to flow into the tank when an excessive vacuum is created in the tank, following the consumption of fuel (ventilation function). In this case, when the vacuum exceeds the load of the spring (4), it moves the valve (3), allowing air to enter.
