My '98 A6 Quattro has got an intermittent whining fuel pump. When it was in the garage for a service the mechanic told me that the Quattro has two fuel pumps because the tank is split into two halves, the prop shaft being the reason why.

I was told that one pump sends fuel up the engine and the other pumps fuel backwards and forwards between the two halves of the tank to keep the levels the same in each tank.

Can anyone confirm this is the case, and say which pump does what? Also are the two pumps the same part number? I haven't got a workshop manual, though there is a good guide about changing the pump on Audiworld.

I was going to change the fuel filter at the same time, and the thought did occur to me that it might actually be the filter that is causing the pump to whine, if so it would have to be the pump that sends fuel to engine that is the noisy one.

I'm in the UK, so driver side is on the right as you look at the car from the back!

Any advice about the fuel pump setup on the A6 Quattro would be much appreciated.

 

i have the same noise from my pump, when i bought the car it would whine intermitently at any time, i thought the fuel pump was fault and purchased a new one at £140. and fitted it which was a tricky job to disconnect the pipes with the restricted access.

a couple of days later i had the same noise again.

i checked and replace the fuel filter - still had the noise.

it would seem that i get the noise less frequently now, and it seems to now occur at times when an increased fuel supply is required, at first start up and under hard acceleration.

there are two pumps in the tank as you described however only one is electricly powered, the second is called a suction jet pump and is linked to the first pump.

i am suspecting i have a problem in this area, but have not got around to checking it yet, i am going to remove the inspection plate at some point to check the pickup for this pump.

just thought i would pass this on as like me you may spend the cash to find you still have the noise. if you need pictures of the set up email me and i will send them

matt

 

Thanks for the information.

So it's not as straightforward as I was hoping it would be.

I'm getting the whining nearly all the time now, it started off very intermittent. I first heard it about 18 months ago, and could always get rid of the noise by stopping and restarting the engine. Now it's mostly there on every journey. I've been quoted over £300 to fix it, so really looking for a DIY solution.

It's really hard to pin down the exact source of the whining, it resonates inside the fuel tank making it difficult to pin down which side it's coming from.

The offside pump would be the powered one then, and do the job of pumping fuel through the filter.

Couple of questions I'd like to ask as you've done some work I'm planning on doing. First off, how low should the tank be on fuel when opening the inspection cover to avoid fuel spilling out? I was thinking running it down to 1/4 full, would that be low enough? I think I should open them both up and have a look, although following your advice should look at the passenger side one first.

Secondly, I should replace the filter to eliminate that. I've got a new filter from an online shop, but it didn't come with any copper washers. Did you use new ones, and do you happen to know what size they are?

The offer to send me the photos is a good one, thank you and I'll e-mail you separately.

 

only one pump as far as im aware and its in the gas tank, the early cars that had the pump on the outside had a sump pump in the tank, 1998 A6Q is in the tank

 

i have just sent you and email with images of the tank.

just thinking, my problem was worse when i had a problem with vacuum in my tank, do you have any hissing from the fuel cap when the nosie occurs?

matt

 

Thanks for the e-mail.

The description of how fuel pumps on the quattro seems very complicated. I'm not sure I fully understand it. As for these 'suction jet pumps' that work without power and seem to rely on uneven pressure to work, well I'm a bit lost!

Anyway thank you for sending all the info. I only received one picture though, just the one that shows the tool for removing the cover.

I discovered today that the whining is definitely coming from the LHS (ie suction pump). I almost found by accident that by pressing on the pump housing (after removing the black cover), changes the pitch of the noise. I've got too much fuel in the tank just now to take a look inside, so will attempt that when I can. Just hoping that in practice it will be easier to see why it's noisy than work out how it works.

I haven't noticed any hissing from the filler cap, but when I get a chance will investigate.

Thanks again, and if you could resent the pics I would appreciate it.

Cheers!

 

if you hear a difference on noise then its the gasket/ seal that's the problem not the pump same as me my bones ache easily with age

 

Thanks for that Dave, sounds like some good news - though I know what you mean about aching bones!

I wonder if all this noise could be down to a poorly gasket? I was tempted to try turning the fitting a little, but the tank is pretty full now - so resisted just in case.

Next chance I get I'll try tightening/loosening and see what happens.