05SilverA8

The pumps remove from the top, but one hose connect inside the tank to the other pump. My mechanic was complaining about how he had to grab the hoses with very long pliers to connect them back together, as they were moving all around. My tank was 1/2 full so it was not that big of an issue with the gas.

DA8

OK here is what it does.

I tested it some more. I cleaned out all my stuff from the trunk, removed the carpet and spare tire and the fuel pump top covers to expose the wire connectors and hoses for the pumps.

Then I started the car and ran to the back to see what was going on in there. The drivers side pump is running for sure and makes a normal pump sound but I cannot tell if the passenger side one is running at all. When I listen on the passenger side I can just hear some pump noise from the drivers side pump and some gurgling fuel sounds from inside the tank.

Then, after 20-30 seconds of running the drivers side pump stops running. The car dies in less than 2 seconds after the pump stops running. Then the driver's side pump starts back up again sputtering for like 1-2 seconds. Then everything is dead.

Go back in the car and turn the key off, turn the key back on and start up - it will go through the whole process described above again.

Has anybody who had this happen before say what it is?

For sure, the car dies right after the pump quits making noise. Is it shutting off because it is bad? or is there something else that is shutting the pump off.

The reason I ask all these questions is because it seems like a simple problem that is strait forward. But with so many systems in these cars. I don't take anything at face value about diagnosis.

Do I replace both pumps? Is that definitely it?

DA8

She is back on the road now. The new passenger side fuel pump did the trick. It was not hard to change out as long as I went slow and followed Bentley instructions. Breathing the gas in the trunk of the car was no fun though.

I think the reason the right side pump fails is because it is pumping constantly whenever the car is running, vs the left side pump which only runs at start up, over 3000 rpm, and when fuel is needed to be transferred to the right side of the tank to balance the supply. The right pump is actually called the main pump, and the left pump is called the transfer pump. It is much easier to understand when I use these terms. Watch out when you are looking at pictures too, they can throw you off because the orientation of the tank changes in different illustrations. The long wings of the tank that the pumps are going down into are actually going down under the seats. and the back side of the tank (or full horizontal top) is just sitting along the back side of the rear luggage compartment.

I ordered a new left side transfer pump because I don't want to take a chance and go through this again. Besides now I have the special lock ring tool. That cost $100. You do need this tool to remove the lock ring.

One other piece of advice. Order two new gaskets even if you are just replacing the one main pump. This is because you have to remove the cap on the left pump to disconnect the transfer hose when you are replacing the right main pump. The person at the parts counter of the dealer does not know this.

Eric04D3A8L

Same problem happened to me 2 days ago.
towed it to the dealership. it stalled once more when they took her into the service bay, but as soon as it was on the lift, she runs fine without shutting off.

The transfer pump (driver side) definitely works since it starts.
so should I be safe and tell them to replace the main pump anyways?

It's currently undergoing 115,000 km service as well (time belt job etc.) someone mentioned the fuel filter needs to be replaced too? is this included in the 115,000km service or should i tell them to do so?

Also, the gaskets mentioned earlier that needs to be replaced, do you have parts codes for them, and why do they need to be replaced once taken off??

DA8

Yes. Definitely if the fuel pump is the problem, replace the main (passenger side, right) pump. Everything I have heard is that this is the one that fails. AudiUSAparts.com told me they only stock the right one because that is what has been failing. The other reason I say this is because I first replaced the right (main) pump. When replaced the problem was resolved and car ran great. As a precaution I replaced the left (transfer) pump the next weekend. What I found in this process was that the right main pump was way dirtier than the left pump (by observing the filter on the bottom of the pump). I believe the actual pump motor units are the same motor, the only difference between the two pumps is the housings and hoses. But the reason the main pump fails is because it gets a lot more use. The transfer pump only is used at start up, transferring fuel to maintain tank equality, and at heavy loads above 3000 RPM. Thus this is why the main pump fails first. My main pump filter was twice as dirty as my transfer pump filter.

It is possible the transfer pump could have lasted the time of 2 main pumps, but I replaced it anyway as a precaution.

You need to replace the gaskets too. The dealer will know this because it says so in the manual. The gaskets seal off the opening in the trunk where you access the pump. This is the cheap part of the fix.

I recommend replacing your fuel filter too. As is stated elsewhere in the forum, Manufacturers do not recommend filter replacement like they used to because they have larger filters than in the past and the pressurized systems operate fine even when the filter is old. However, the reason they operate fine is because the fuel pump is pressurizing them. If the filter is giving more resistance, the pump has to work harder and will fail sooner. I replaced my filter, then gave it an autopsy by cutting it in half with a hack saw. The filter media inside was black with deposits. No wonder the pump failed.

Here is how to tell if your main pump is failing. In preliminary failure state car will run fine, then suddenly not have any power from idle. 1-3K RPM will be void and car will sputter like it is not getting any fuel. Then it will go away. This is what my A8 did at first and why I thought it was other things like MAF and vacuum leaks. But in about 300 or so miles the day came when it totally failed, and I had to have the car towed home from work.

In total failure mode car will start. It starts because the transfer pump is pressurizing the system. The car will run for 20-40 seconds and stall out. You can start the car and move it for this time, but it will totally stall out. You can start the car and run to the trunk and put your head in all the way to the back seat. You will not hear noise from the right side (main) pump, but if you are quick enough and get in there before it stalls you will hear noise from the left (transfer) pump for 20-40 seconds. Then you will hear the transfer pump shut off and the car will immediately stall. Then you will hear the transfer pump start for 1-2 seconds and stop.

Hope this helps you and anybody else with a D3 A8 resolve the problem. I believe it to be a common problem at around 100K miles or less.

mishar

Can you please point to the source of this information.

DA8

When your pump fails you will not be asking me that.

DA8

Sorry Mishar, I could not resist that one. And you have to admit you asked for it. I mean, Come on! That is such an old standby. "tell me what publication." Especially after I just told you how I arrived at the conclusion.

The truth is that I had to triangulate the information. The SSP or SSDs or whatever they are called do not supply the full picture of information and they are confusing in their partiality. They call it a right main fuel pump when it is on the left side of the page and don't tell you that the illustration is actually inverted. That is why there is so much myth here on the forums. That is why the techs get paid so much to diagnose and even they cant get it right but a % of the time. The incentive is not for the manufacturers to supply all the info to us. I scoured the web and the manuals for the information and got bits and pieces from diverse sources. I put so much time in it that it would have been way cheaper to pay the dealer to fix it for me. But that is what I do for the learning experience like a lot of people here so I can embrace my rugged individualism. And I am not going to re-spend all that time now to make a detailed list of publications to address your bruised ego.

The real proof is in the pudding. I found out how it really works after reading everything then experimenting with the car itself, by taking it apart and fixing it and getting the neoprene gloves on my hands dirty and developing a splitting headache from the fuel in the trunk. Trust me that is how it works or at least VERY close to how it works. Anybody who has this problem and searches this information will benefit from my experience.

mishar

Well, that's exactly what I am trying to do. To benefit from your experience. But you shouldn't expect me to take it as a truth just like that. That wouldn't be right way of building knowledge. Some brain storming may clear some weak spots and benefit both of us.

DA8

Your right Mishar. I was too harsh. I am sensitive about some things and that got my hackles up. Sorry. I have got to go to bed now.

Thanks for your help.