A fuel gauge sensor is installed at the top of the fuel tank (in the combined instrument panel), as well as supply and return fuel lines. These pipelines must withstand a high operating pressure of 3 bar. For this reason, these pipes are made of a particularly robust material and are fastened at the factory with band clamps or clamps with a bolt and nut. For safety reasons, only branded band clamps should be used when replacing. Screw terminals are not allowed!
Ingenious ventilation system
The pump supplies fuel through a piping system from the tank to the engine. A fuel filter is built into the supply line. Pipelines for venting the tank are also connected to the filler neck. When fuel is poured into the tank, air is removed from the tank through this ingenious system. During driving, outside air rushes into the tank through this pipeline, depending on the amount of air used, so there is no vacuum in the tank.
Of course, the fuel tank vent pipe does not just go out. The appropriate treatment of harmful fuel vapors is ensured by a special exhaust ventilation system. Fuel vapors are discharged into the activated charcoal tank and then added to the fuel intended for combustion.
Feed system with fuel recirculation: 1 - fuel tank, 2 - fuel pump module, 3 - fuel filter, 4 - fuel pressure regulator, 5 - injector.
Cleanliness rules
When working on the fuel supply and injection system, Audi recommends the following six rules:
- 1. Joints and adjacent parts must be thoroughly cleaned before loosening.
- 2. Place the removed parts on a clean stand and cover them. Do not use soaked rags!
- 3. If repair is not to be carried out immediately, carefully cover or cover exposed parts.
- 4. Install only clean parts. Remove the spare parts from the packaging immediately before installation. Do not use parts that have been stored unpackaged (e.g. in tool boxes, etc.).
- 5. Do not work with compressed air when the system is open. If possible, do not move the vehicle.
- 6. Protect disconnected plug connections from dirt and moisture; only dry plugs can be connected.
The principle of operation of the jet pump
On all-wheel drive models, the fuel tank is divided into a left and right chamber. So that fuel from the left half of the tank can be supplied to the fuel pump module 8 (to petrol pump), which is located in the right half of the tank, a jet pump 1 is needed. The second jet pump 7 is located in the right chamber, it improves the fuel supply to the gasoline pump.
Only the jet pump that is located on the left side of the fuel tank 1 is removed. The pump, which is located on the right 7, is an integral part of the fuel pump module, it cannot be changed separately
The jet pumps operate according to a simple physical principle: the motive jet from the return line 3 in the jet pumps 1 and 7 passes through a nozzle and is therefore accelerated. Due to this acceleration, nearby fuel is involved in the movement, which is injected into the fuel pump module. The right jet pump 7 supplies fuel directly to the module housing, and the left pump 1 through a separate pipeline 4. Through the tee 2, fuel from the return fuel line is distributed to both jet pumps. The distributor 6 limits the pressure in the pipelines that go to the jet pumps to about one bar. Excess fuel is diverted through the pipeline to the housing of the fuel pump module. The arrow in the figure indicates the direction of movement. The fuel supply line 5 is located on the fuel pump module.
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