The fuel level sensor consists of a float and a potentiometer. When the fuel level drops, the float also drops. A potentiometer connected to the float increases the resistance of the sensor. Thus, the voltage on the instrument panel decreases and the fuel gauge moves in the direction «empty». For vehicles with a two-piece fuel tank, the processor calculates the total fuel supply from both sensors, controlling the fuel gauge on the instrument panel.
Warning: When removing the fuel pump, some fuel may leak out. Fuel vapors are poisonous and flammable, therefore, particularly good ventilation of the workplace must be ensured. Avoid skin contact with fuel. Use gloves that are resistant to fuel. Do not use open fire. There is a risk of fire! Keep a fire extinguisher ready.
Warning: Before removing the fuel pump and reserve sensor, it is advisable to empty the tank. To ventilate the workplace, a radial fan can be used, the electric motor of which is located outside the air flow.
Withdrawal
1. Disconnect the negative cable (–) battery with the ignition off.
Warning: As a result, information is erased from the electronic memory units, such as the code of the radio receiver. Without a code, the radio can only be switched on by the manufacturer or an AUDI workshop. Therefore, read the materials of the subsection Entering the radio code.
2. Tilt the rear seat and unscrew the cover of the fuel reserve sensor and fuel pump.
Warning: The fuel system is under pressure! Before opening the hose connections, place a thick rag on it. Then carefully open the hose and release the pressure. Use protective goggles when doing this.
3. Disconnect the supply -2- and return -1- pipelines by squeezing the stoppers on the quick couplings. Close the pipelines with stoppers, for example, a bolt with sealant.
4. Disconnect the fuel reserve/fuel pump sensor connector.
5. Loosen the union nut with the special tool AUDI-3217.
Warning: If the specified tool is not available, loosen the nut using a block of wood and light hammer blows.
Warning: Never allow sparks to form.
6. Remove the pump block/reserve sensor and O-ring from the fuel tank opening.
7. Drain the fuel from the pump unit into a tank or suitable container.
8. Remove the fuel reserve sensor if necessary. To do this, release the wire connections -3- and -4-. Raise the locking bars -1- and -2- with a screwdriver and remove the sensor downwards.
Installation
1. Insert the sensor into the guides on the holder and push up until it locks. Connect the electrical wires at the reserve sensor.
2. Install the pump block in the fuel tank. Be careful not to bend the fuel gauge sensor. Moisten the sealing ring with fuel before installation.
3. Check the position of the flange. The arrow on the cap must point in the direction of the arrow on the tank, refer to the illustration.
4. Tighten the union nut with the special tool AUDI-3217, torque 60 Nm. You can tighten the flare nut with light hammer blows through a block of wood.
5. Connect the supply and return hoses, making sure the quick couplings lock into place. When fastening, use new band clamps. The return hose is blue supply black. The arrows on the flange indicate the direction of fluid flow.
6. Connect electrical connections.
7. Attach the fuel reserve sensor cover.
8. Replace the back seat.
9. Attach the negative cable (–) to the battery.
Warning: Activate the automatic safety power windows, enter the radio code, set the clock, while referring to the subsection Entering the radio code.
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