Fuel pump problem, stalls when assembly is tight and when under 1/2
 

The fuel pump on my 1997 A8 recently died, so I bought a new one (OEM same exact pump).

Removed the whole plastic assembly out of the tank and replaced the fuel pump. Put everything back together, started the car and everything was fine.

After about 4-5 minutes, the pump started making noise (as if it was starving) and the car stalled. Disassembled the whole thing and reassembled a few times making sure everything was in its correct position (pickup tube, rubber lines, etc.) and the same thing keeps happening (pump starving).

After trying many things, figured out that when I leave the long bolt and the plastic ring loose, it works fine with over 1/2 a tank (under 1/2 a tank, nothing works)

-Does anyone have a picture or a schematic, or could even explain what are the other parts IN the tank (what the removable assembly bolts-on to) because I think there is something wrong with mine (maybe crack, moved, idk..)

-Is there a way to recalibrate the fuel gauge.. My cluster says 1/2 and it's maybe right, but my tank does not seem to be 1/2 full through the fuel pump hole.



My dad (VW/Audi tech for nearly 30 years) and I have been working on this and can't figure out what were doing wrong...


Thanks alot

are you absolutely certain that the pump sits flush w/o any tension? I don't know if you saw the youtube videos I did but that's a mistake I made. I didn't have the rubber gasket seated all the way around so it "felt" like the bolt was tight but it wasn't.

Did you get the gasket kit as well? I recommend that, it's a rip off but the seal on the bottom of the pump housing is critical. If the old one is too compressed it won't seal correctly.

Do you have a borescope? It'll only take you another 15 mins if you remove the other sending unit and be 100% certain the pick up tubes are lining up.

Are you certain that the pump is fully seated in the plastic pump housing? Another easy thing to miss (again see my video). The clips should be on top of the metal part of the fuel pump. If not, the pump isn't seated all the way at the bottom.

Try to check everything in one shot. It's easy to keep trying and retrying (been there) but the more times you remove/install the higher likelyhood of breaking something. Plus it's really frustrating to put it all back together only to have it die in 5 mins. It's something related to the pick up tube, you're not getting fuel from the other side. I'm not sure what leaving the bolt is is doing though to change that.

As far as the internals, just look straight down with the pump out. You'll see where the bolt threads into and the female part of the pick up tube on the left side.

Get the borescope! It's one of the best tools I ever bought for the garage and has saved me countless times.

Bob