Table of contents: Fuel filter for cars with gasoline… ↓ Fuel filter for cars with diesel… ↓ Condensate - drain ↓ Fuel filter - replacement ↓
Fuel filter for cars with gasoline engines
The design of the fuel filter of AUDI 80 cars with a petrol engine is such that it does not need to be changed throughout the entire service life of the engine. This has its advantages, because to remove the fuel filter in quattro models, it is also necessary to dismantle the fuel tank. And this in turn is possible only after dismantling the rear axle. For this reason, we recommend changing the fuel filter only if necessary due to a malfunction of the fuel system.
Fuel filter for cars with diesel engine
The distribution fuel injection pump of diesel engines is very sensitive to fuel contamination, especially water. As a rule, fuel contaminants clog the connecting pipe of the return hose and the fuel injection pump overheats. Water gets into diesel fuel during refueling or accumulates as a result of its condensation. For this reason, the fuel must be cleaned of liquid and solid impurities before it gets into the fuel injection pump. This function is performed by the fuel filter, the replaceable filter element of which retains all solid impurities, and condensate, which is heavier than fuel, collects at the bottom of the filter.
TDI engines have a condensate level sensor, which is located at the bottom of the filter instead of the threaded plug of the condensate drain hole. This sensor works on a simple principle. Power is supplied to the two electrodes of the fuel filter. As soon as the condensate level reaches the electrodes, the resistance in the circuit changes, which in turn is recognized by the control unit (see illustration 4.0b).
Condensate - drain
1. Unscrew the vent plug at the top of the filter.
2. Loosen the clamps securing the inlet and return hoses to the fuel filter. The clamps can be loosened with a small screwdriver by widening the eye. The same clamps can be reused by squeezing the eye with side cutters (see illustration). We recommend installing new clamps.
3. Unscrew the filter mounting nut (see illustration 4.10).
4. Pull the filter out of the holder by pushing it upwards. For TDI engines, disconnect the condensate level sensor plug to do this.
5. Place a container under the fuel filter to collect condensate.
6. Unscrew the threaded plug of the condensate drain hole at the bottom of the fuel filter by hand. Be careful. The threaded plug is quite fragile. TDI engines have a condensate level sensor screwed in instead of a plug.
7. Drain the condensate (it's about 100 cm³). Continue this procedure until clean fuel begins to flow from the drain hole.
8. Screw in the vent and drain plugs.
Fuel filter - replacement
9. TDI engines only: Disconnect the condensate level sensor plug and remove the plug from the bracket (see illustration).
10. Loosen the clamps securing the inlet and return hoses to the fuel filter and remove the hoses (see illustration).
11. Unscrew the filter mounting nut and remove the filter (see illustration 4.10).
12. Remove the protective foil from the fuel filter.
13. Disconnect the fuel filter from the mounting flange.
14. Drain any remaining fuel from the fuel filter into a suitable container.
15. Install a new fuel filter.
16. TDI engines only: Screw the condensate level sensor into the new fuel filter.
17. Operate the starter until fuel begins to flow to the high-pressure fuel pump.
Attention! Do not throw away the old fuel filter together with household waste. It is subject to recycling.
Caution: If diesel fuel gets on the coolant hoses, the hoses should be cleaned immediately.
Note: There is a sieve in the fuel gauge sensor intake cradle. To clean it, the fuel gauge sensor must be removed.
