The fuel pump in your vehicle is essential for delivering the proper amount of fuel at the correct pressure. Usually, they fail unexpectedly and at the worst possible time.
Disconnect the negative ground of the battery — I suppose this is optional, but probably a good idea since sparks are not preferred when working around gasoline.
Remove the rear seat bottom. It is held in by two clips, so just yank up on it sharply and it should unclip. (This is also a good time to vacuum out all the crap that has collected between the seat backs and bottom.)
The quattro actually has two pumps: The secondary pump moves gas from the left side to the right, over the differential that sits under the middle of the tank. The primary pump is on the right (passenger) side. Unscrew the three screws holding the cover.
Pry off the electrical connector for the pump.
Remove the two hoses. They each have a button that presses in, which allows the connection to lift off. (Screwdriver tip is touching it in this pic.) Have a few rags ready, since supposedly these are under pressure, but my car had been sitting a while so nothing really came out when I pulled off the connectors.
Pay attention to the two arrows in this pic — one on the pump and one on the fuel tank (where I wiped the dirt away). These need to be lined up when you put your new pump in.
Next remove the big threaded nut that holds the pump in. Audi has a special tool for this, but I placed a flat-bladed screwdriver on one of the lugs and tapped on it with a hammer, which rotated it off. The pump should pop up when the piece comes off.
Lift the top of the pump off and remove the rubber gasket.
Reach inside and disconnect the plug for secondary pump wiring harness. Disconnect the fuel line by pushing on the release button and sliding it off.
Next there is a plastic bracket that needs to be unhooked from the pump. It holds the secondary pump return hose. You have to reach pretty far in the tank to get at it, but it slides up and off the pump. You can see it on the right side of the pump in this shot.
Now you can work the pump out of the hole. Have a bucket ready to put the pump in, since it may still have gasoline in it that will leak all over. Make sure you use an official Audi bucket; no other bucket will work for this…
Feed your new pump into the hole and start reattaching everything, including the plastic bracket, the secondary pump hose, and the secondary pump wiring harness.
Put on a new gasket. This gasket goes on the inside edge of the opening.
Replace the top piece.
Replace your nut; tighten it up the same way you took it off. Make sure you line up the arrow on the pump with the arrow on the tank.
Snap on the connectors.
Reattach and tighten the battery cable, turn on the ignition, cross your fingers, and try to start it. Mine didn’t start right away — had to crank for a while until it finally caught, which I assume was due to a dry pump that had to prime itself. Replace the cover, clean everything up and put the seat back in.