2582289 - 1080E EVAPORATION CONTROL SYSTEM

The evaporation control system consists of:

  • fuel tank
  • vapour separators,
  • two float valves,
  • a two-way ventilation valve inside the fuel tank filler cap,
  • an active carbon filter with a filter flushing solenoid controlled by the IAW 59F engine control unit
1, Fuel tank2, Vapour separator with multifunction valve3, Float valve4, Plug with pressure relief valve5, Engine control unit6, Active carbon filter7, Carbon filter flushing solenoid8, Intake manifoldThe vapours coming from the tank through the two float valves (3) are sent to the separator (2).The vapours condensed in the separator (2) fall back into the fuel tank.Uncondensed vapours are sent through a multi-purpose valve in the separator (2) and the pipe to the canister (6), where they are absorbed and stored by the activated charcoal in the filter.Vapours are conveyed to the engine intake duct through solenoid (7) controlled by the engine control unit.

FLOAT VALVE

This type of valve is used for carrying out the following functions:

  • prevent liquid fuel emerging from the tank in the case of roll-over,
  • allow fuel vapours from the tank to be vented to the separator and activated charcoal filter;
  • allow tank ventilation if there is a vacuum inside.
The float valve consists of a body (1) and a float/needle valve (2).Valve operation may be summarised as follows; depending on the level to which the fuel tank is filled.

MAXIMUM TANK LEVEL

If the tank is full, float (2) blocks port (3) preventing the liquid fuel from reaching the separator.

INTERMEDIATE TANK LEVEL

If the level of the fuel in the tank decreases, the float (2) descends and rests via its side tabs (4) on the slits in the valve body (1) to open the port (3). The gas reaches the port through the ring section between the float (2) and the inner seat of valve body (1).This allows the fuel vapours to escape from the tank and reach the separator.The tank can be ventilated through the same circuit when the pressure inside is less than the pressure outside.

SEAL IN THE EVENT OF ROLL-OVER

if the vehicle rolls over, however full the tank is, float (2) presses down on hole (3) under its own weight and that of the fuel to prevent a dangerous outflow of fuel to the active carbon filter and the consequent risk of the vehicle catching fire.

FUEL VAPOUR FILTER (CANISTER)

Fitted in the front right wheelarch, this consists of an activated-charcoal filter element which absorbs the fuel vapours coming from the separator.A one-way valve (3) 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 (1) to the inlet manifold when the fuel vapour solenoid valve is opened by the engine control unit.
1, From the multifunction valve2, To the inlet manifold3, One-way scrubbing valve4, Fuel vapour solenoid valve

ACTIVE CARBON FILTER SCAVENGING SOLENOID

This is fitted directly to the inlet manifold, and is controlled by the fuel engine 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 closed to prevent the fuel vapours from reaching the intake manifold.

ACTIVE CARBON FILTER SCAVENGING SOLENOID

When the engine control unit controls the fuel vapour solenoid, solenoid (1) is excited and attracts plunger (2), which overcomes the load of laminar spring (2) to bring the canister into communication with the engine intake manifold.

MULTI-PURPOSE VALVE

The multi-purpose valve has the following functions:

  • to prevent excess pressure in the tank
  • to prevent a vacuum in the tank
  • to prevent fuel emerging in the case of roll-over

TANK OVER-PRESSURE

The tank is maintained at a pressure of 30-45 mbar by means of a fluorosilicone rubber valve, which rests on a sealing edge.The valve is supported by a stainless steel plate and counteracted by a spring.When the pressure in the tank exceeds the specified value, it overcomes the resistance of the spring and the valve is able to rise, allowing vapours to flow out to the canister. The valve closes again when the pressure falls back to within tank pressurisation limits.

TANK VACUUM

Under particular driving conditions, a vacuum could be created in the tank because of:

  • temperature changes
  • fuel consumption.
Under the above conditions, the valve makes up pressure in the fuel tank by adding extra air.A fault in this function could cause the engine to miss or stall, because of difficulties in supplying the fuel pump.This function is carried out by the ''goose beak'' valve formed directly out of the fluorosilicone rubber.

SEAL IN THE EVENT OF ROLL-OVER

If the vehicle should roll over or tilt to a great extent, the multifunction valve acts to contain the emergence of fuel from the tank.During normal driving of the vehicle (bends, acceleration, braking, etc.), the fuel slops around and may spill into the canister. The high sensitivity of the multifunction valve prevents such spillages.Valve closure angle is about 33°.

SAFETY AND VENTILATION VALVE

This valve is built into the fuel filler cap. Its operation is dependent upon pressure in the fuel tank and is as follows:

  • – (safety function) discharges excessive pressure which forms inside the tank; the pressure acts on the plate (2) and, overcoming the load of the spring (1), allows excess vapours to be discharged outside (ventilation function).
  • It allows external air to flow into the tank when an excessive vacuum is created in the tank, following the consumption of fuel. In this case the vacuum overcomes the load of spring (4) to move valve (3) and allow air to be taken into the fuel tank.