Audi 80/Avant (B4)

since 1991-1995 release

Repair and operation of the car



Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
+ Cooling system
- Fuel tank and fuel pump
   Fuel tank
   Fuel level sensor
   Fuel accumulator
   Fuel-supply line
   Fuel pump
   Replacement of the fuel filter
+ Air filter and airintaking channels
+ System of injection
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
+ System of ignition
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications




Fuel tank

The fuel tank of the Audi 80 car is technically rather perfect, but also it was improved for all-wheel drive models. The difficult form of a fuel tank helps to achieve a high-capacity tank without prejudice to the volume of a luggage compartment. In the middle of a fuel tank you see the fuel pump and the sensor of the indicator of amount of fuel. On the right above a bulk branch pipe with all ventilating and bulk hoses.


Back right wheel niche with the removed flap

1 – bulk branch pipe;
2 – drift valve;

3 — a fuel tank;
4 — a broad tank.

The fuel tank in the front-wheel Audi 80 models has volume about 66 l, in all-wheel drive versions it contains at least 64 l. To reach a flat surface of the bottom of a luggage compartment with possibility of loading of salon, the fuel tank is established in a car stern under the sheet bottom of a luggage compartment. The tank is made of plastic – the material allowing almost unlimited opportunities when giving a form. These opportunities were used for all hundred percent. For example, the fuel tank of all-wheel drive models occupies practically all free spaces under the body bottom that becomes to achieve perhaps bigger volume. Therefore the form of this detail of the car looks quite strange. In order that during a trip also the parts of a fuel tank located below were emptied skillful reception was applied: in this lower area there is a pump, at the working engine constantly pumping over fuel in the parts of a fuel tank located above. And it occurs quite simply: returnable fuel from a drain fuel-supply line picks up additional fuel in a pump housing and transfers it upward.

One more reception was applied to cope with chambers of various volume in a fuel tank: the hose conducting directly in absorption area so it is filled first of all is connected to a bulk branch pipe. It is important, for example, in a case when a small amount of fuel from the spare canister is added.

 Help: before starting working with a fuel supply system, you surely have to disconnect the grounding cable from the battery. Inadvertent electric short circuits can serve as the reason of dangerous iskroobrazovaniye.

For what ventilation of a fuel tank is necessary?

  • Ventilation of a fuel tank is important for uninterrupted supply of fuel: in the same quantity in which fuel is spent, air has to come to a tank, otherwise in a fuel tank the lowered pressure is formed, and intake of fuel will stop.
  • It is necessary to ventilate a fuel tank to give to its contents the chance to expansion when heating.
  • During filling it is necessary that air could leave a tank because differently the poured fuel again will rise to a bulk branch pipe and will start pouring out.

Ventilation of a fuel tank in the Audi 80 car

  • Directly behind a bulk branch pipe the ventilating pipeline of a fuel tank is connected. The ventilating channel conducts at first in the so-called valve of drift. The last closes the pipeline as soon as the car bends aside more than on 45 °. Thus leak of fuel via ventilating channels at accidents is prevented. After passing of the air valve the ventilating pipeline conducts, however, not at once outside, and comes to an end in a tank with absorbent carbon in the right forward wheel niche. Its appointment – to catch fuel couples passing through this pipeline (which arose, for example, as a result of a warming up of contents of a fuel tank). At the working engine these gases at a certain loading of the engine again are exhausted from a tank with absorbent carbon. When it has to occur, defines the electromagnetic valve operated depending on loading.
  • In parallel to this system the air valve opens when filling the broad tank of a fuel tank located in the bulk channel (in the right back wheel niche) in the form of separate capacity. Thus, at the increasing fuel level fuel couples can be forced out there instead of to them to disappear in the atmosphere.
  • During the movement on this way external air depending on the spent amount of fuel so in a tank it is not formed depression arrives.