Audi A4

Since 1994 of release

Repair and car operation

The electromagnetic valve of the coal filter is at the left below behind in an impellent compartment

Ventilation of a fuel tank is important for faultless giving of fuel: in that volume in what fuel is spent, air should get into a fuel tank, differently in a fuel tank the lowered pressure is formed, and fuel giving will stop.

Further the fuel tank should be ventilated that fuel had a possibility for expansion at heating. At a gulf of fuel from a fuel tank air enough should be superseded that filled in fuel did not pour out through a jellied branch pipe.

Ventilation of a fuel tank in Audi A4

• Above in a fuel tank the ventilating tube is connected. In the beginning it goes through connecting knot on a jellied branch pipe to the so-called gravitational valve. It closes a tube as soon as the car bends sideways more than on 45 . In such a way fuel pouring out through a ventilating tube is not supposed at failures.
• Therefrom the ventilating tube is deduced not simply outside, and enters into the coal filter in the right forward wheel niche. The purpose of such device consists in catching of the fuel steams harmful to environment acting through this tube (arising, for example, at the expense of heating of a contained fuel tank). When the engine works, at certain loading on it gases again are sucked away from the coal filter. When it occurs, defines the electromagnetic valve operated injection of fuel.
• In parallel this system there is a high-speed ventilation which conducts to a jellied branch pipe through the compensating volume in the form of special purpose capacity in jellied mine of a fuel tank. This way of ventilation matters, first of all at refuelling when fuel level quickly rises, and fuel steams should be superseded but so that not to get to atmosphere in too considerable quantity.
• During movement by the same way to a fuel tank atmospheric air according to spent fuel gets, therefore in a fuel tank the lowered pressure cannot be formed.