UrS4boy

Our C4 UrS sedans and avants have three fuel lines, as shown in the schematic below (note the hyperlinks to more info are underlined)

1. A high pressure feed line from the fuel tank and 091G pump to the fuel filter, fuel rail and injectors and fuel pressure regulator,
2. A low pressure returnline from the fuel pressure regulator back to the fuel tank and
3. A fuel vapour line to the fuel emissions canister.



Here is the fuel tank and inlet parts, note Item 6 the retaining ring used to hold the top of the fuel sender plate tight to the fuel tank.



To ensure no fuel or vapour leaks, there is a large O-ring that sits between the top of the tank and the bottom of the fuel lever sender plate (Item 4 here):



Here is an example C4 fuel sender coming out of the tank:



Here are the fuel lines:



At this point in their lives, you might want to check your fuel lines and, as need be, use Fred Munro's Fuel Line Maintenance DIY pdf

Better safe than sorry.

GoHeels

Good stuff Dave. There's more going on with the fuel system than I realized. After going into the tank for the fuel pump last week, I was wondering what some of the extra hoses were for. Tremendous job putting these features together about the various systems and components of our Audis, and hyperlinking them together. It's certainly easier to work on the car or figure out what's wrong with it when you have a good understanding of how it works.

UrS4boy

That's why I do these things.