Audi is a luxury auto manufacturer based in Germany, and its cars feature advanced technology and engineering. The fuel-level sending unit in an Audi vehicle is no exception. This feature sends the dash fuel gauge the proper information as to fuel level in the tank. Rather than lifting the vehicle to replace the fuel-level sending unit, you can access the fuel pump and sending unit in the boot.
Make sure the fuel tank is below half full. If it is not, drive the vehicle around until it is. Relieve pressure from the fuel lines before accessing the fuel level sending unit. Remove the fuel filler cap and the fuel pump relay from the engine bay fuse box. Crank the engine, and let the fuel lines empty; the engine will sputter and shut off. Disconnect the negative battery cable.
Open the boot, and remove the carpet and the boot liner. Locate the fuel pump access cover plate close to the rear seat. Remove the plate with the Phillips screwdriver.
Disconnect the wiring harness and fuel lines. Label the lines for input and output to properly reconnect them to the new fuel level sending unit.
Use Audi tool #3307 if the vehicle is an Audi A4. The Audi A4 fuel-level sending unit is attached to the fuel pump. Use the tool to remove the fuel pump to access the sending unit. Remove the fuel-level sending unit. For all other Audi vehicles, use Audi tool #3217 to remove the fuel-level sending unit plastic locking ring.
Install the new sending unit, and secure with the appropriate Audi tool. Replace the fuel pump for A4 vehicles. Reattach the fuel lines for input and output. Connect the wiring harness and replace the fuel pump access cover.
Replace the boot liner trim and the carpet. Attach the fuel filler cap, the fuel pump relay and the negative battery terminal. Start the engine, and check underneath for fuel leaks.
Even after relieving system pressure, the fuel lines will still leak a small amount of fuel. Wrap the unit with a hand towel to prevent it from leaking into the boot.
Exercise extreme caution when working around fuel. No flames or smoking.