69-z28

Well where do I start. About 4 months ago the fuel pump went in our 1999 Audi a8. I brought the car to the dealer and $1500 dollars later we were running again.

Now 4 months later the car shuts off at a half a tank. So I bring the car back to the dealer and they tell me that there are Auxiliary pumps inside the tank that pump the fuel to the main pump and one of those is probably bad and it will be very costly to figure out.

The mechanic tells me just don't let it run under a 1/2 a tank.

From what I read I think their feeding me a line. Whats your oppinons?

tozoM8

There is only one pump. They installed it wrong and it does not pickup the fuel from the driver's side. The whole pump assembly is $650-750 and it takes less than an hour to install it.

dtrotter

I am having the same problem. The 1st Audi tech told me it was the complicated pick up tubes throughout the tank that are bad, and the tank will need to be replaced. The 2nd Audi tech told me the new pump was not "seated" correctly when the 1st tech installed it, and that he re-installed it correctly. I am still having the same problem, but not until the tank is one third to empty.

Kneale Brownson

Did the second guy replace the seals while reinstalling the pump assembly?

dtrotter

I purchased the fuel pump kit assy from a authorized Audi dealer, so I would assume it included the seals, but as my mentor use to tell me: assume is spelled...***, out of, u, and, me

Kneale Brownson

No BTDT yet, but I seem to recall there being a separate seals kit.

SCL

I had the same problem, but now it's fixed...and I'm not sure how.

After giving up on it for 6 months and driving with 2 extra gallons in the trunk for 6 months... I tried to troubleshoot it again, but the problem seemed to have fixed itself somehow.

Initially, whenever I tightened that long bolt, air would come back in the return line and the engine would sputter. By loosening the bolt and breaking the seal between the two halves of the pump assembly, most of the tank would gravity feed to the pump...allowing use of about 2/3 of the tank volume.

Six months later I re-visited the issue... and could not reproduce the problem. I tightened down the bolt, and everything ran fine. I even ran the tank down to empty with an indicated 0 miles remaining, and still no problem.

Maybe air gets into those in-tank tubes and it needs to work itself out. Or maybe you just have to tighten and re-tighten that long bolt until it seats properly.

I've put about 2000 miles on it now...and ran it near empty several times. I did not need to replace any seals... and I did not need to pull out the assembly. I just tightened down the bolt again (maybe the 12th attempt) and the problem was gone.

So...I don't have the exact answer, but I thought maybe my experience might help in some way.

tozoM8

That long bolt pulls the ventury system up to the pump. If is not seated properly to the bottom of the pump assembly it will run out of fuel at 1/2 tank.

SCL

I think I understand the general design, but I don't know how it corrected itself...
I'm sure you know...if the assembly is seated and sealed, and the venturi system is not working, then the fuel pump will not get fuel if the fuel level drops below the top of the assembly...which seems to be about the top 1/3 of the tank. But if the bolt is intentionally loosened, breaking the seal, then the top 2/3 of the tank can gravity feed to the fuel pump cup.

So in my case, it seemed like that hooked tube the sends fuel to the venturi pumps was not seated into the lower assembly. But all I did was to tighten the bolt down again (after driving it for 6 months with the bolt loose) -- and did nothing else that would have changed anything -- and suddenly everything worked as designed.

A8CT

there's a guy who posted the removal, I uploaded swapping the pump into the housing last week.

I have video of the complete pump install which I'll upload in a day or two. I used a borescope so you can actually see the pick up tube and how it needs to seat correctly.


Bob