kcf

my '98 A6 2.8 has begun to lose power when below 1/4 tank. the check engine light comes on and I have to pull over and idle for a few seconds. then I can resume for a minute or so, then the cycle repeats. add a few gallons of fuel and all is ok. I have also noticed the fuel pump sometimes whines real loud.

a non mechanic (but he is a rocket scientist) said the head pressure is lower as the tank empties. if this is causing the problem then the pump is likely going bad. Audi dealer says they rarely replace pumps.

any ideas?? thanks

April

The tanks are pressurized. If they aren't holding pressure, you may get some racket as they try to maintain pressure.

kcf

replaced the large fuel filter. is there another one? if it is the fuel pressure valve, why only below 1/4 tank? where is the fuel pressure valve? fuel pump noise is only when below 1/4 tank and intermittent

thanks for your help

April

why would it only be marginal when you're down to a 1/4 tank? It's an odd problem.

The fuel pressure regulator is up in the engine compartment. Somebody might have a pic for you. Not that it should matter how much fuel is in the tank - just take longer to crank and maybe the pump has to work harder/longer.

Just giving it a shot.

4Driver4

I think you need to pull the pump out and look it over.

4.2bandit

the fuel systems in the A6's are complicated. There are 3 level sending units. Poss. one of them is bad or the siphoning pump is bad on the left side of the tank. You need to remove the covers under the rear seat and remove the caps at the top of the tank to see where the fuel level is when your car acts up. The fuel pumps really never go bad on these cars.

kcf

maybe that cracked pickup makes sense. this problem started after I made an unintended off road excursion. my front left wheel went off the road and when it did, the car hit a rock which cracked the oilpan cover. maybe the fuel pickup or something in the fuel supply system was jarred and cracked/broke at the same time. I did not suspect this problem was related as I did not see any damage other than the cracked oil pan cover. but the fuel supply issue showed up when that tank of gas got low. can I assume the noisy fuel pump is a result of fuel starvation? it only whines when it is below the 1/4 level. when the car is stationary I can hear it, but the car idles fine. when I am driving at below 1/4 tank and the car loses power (does not stall but I can no longer maintain speed) I cannot hear the pump.

should I remove these covers and look?

Thank you

Epicman1

Replace the fuel filter first...it's a lot cheaper than a fuel pump.

kcf

thanks to 4Driver4 for identifying the problem. finally got a chance to open the driver's side fuel tank and the pickup is indeed broken. looks like i need to replace the siphon assembly. there are two hoses that look like they cannot be removed and replaced onto the new part. does this mean I need to replace whatever is in the passenger side tank as well? ideas???

thanks