Fuel Tank

The fuel tank of the Audi 80 is technically quite advanced, and it has been further refined for the all-wheel-drive models. The complex shape of the fuel tank helps achieve a large tank capacity without reducing luggage compartment volume. In the middle of the fuel tank you can see the fuel pump and the fuel level sender. At the top right is the filler neck with all vent and filler hoses.

Rear right wheel well with wheel arch liner removed
1 – filler neck;
2 – check valve;
3 – fuel tank;
4 – expansion tank.

The fuel tank in front-wheel-drive Audi 80 models has a capacity of approximately 66 L; in all-wheel-drive versions it holds at least 64 L. To achieve a flat floor surface in the luggage compartment with the ability to load the cabin, the fuel tank is installed at the rear of the vehicle, under the body floor panel of the luggage compartment. The tank itself is made of plastic, a material that allows almost unlimited possibilities when it comes to shaping. These possibilities have been fully exploited. For example, the tank of the all-wheel-drive models occupies almost all free space under the underbody in order to achieve the greatest possible volume. For this reason, the shape of this component looks rather unusual. To ensure that the lower parts of the fuel tank are also emptied during driving, a clever method is used: in this lower area is a pump which, with the engine running, constantly transfers fuel to the upper parts of the tank. This works quite simply: the return fuel from the drain line picks up additional fuel in the pump housing and carries it upward.

Another method is used to manage fuel tank chambers of different volume: a hose connected to the filler neck leads directly to the suction area, so that this area is filled first. This is important, for example, when a small amount of fuel is added from a spare fuel can.

Note: Before working on the fuel system, you must disconnect the ground cable from the battery. Unintentional electrical short circuits may cause dangerous sparking.