Query about fuel pump noise!

Hi
Looking through the old threads i know fuel pumps/pump noise has been done several times, I'd just like a bit of extra info please! I own a 1996 A4 1.8 petrol, over the last week or two there has been a low
pitched whine coming from the back of the car, same area as the fuel tank but it does not start immediatly, it usually kicks in after about 3 miles. What i have not seen on any other of the threads is the fact that when i brake the pitch of the whine drops but the voulme stays the same (this is the same even when stationary). whilst trying to trace the source of the noise earlier today, i heard quite a loud hissing coming from the filler cap whilst the engin was running (yet there was no smell of petrol so i dont think vapour is actually escaping), as soon as the car was switced off this stopped however, over the last few days i have been hearing a gurgling sound from the tank when i have stopped and got out of the car, this lasts for several seconds then stops. finally the petrol guage has started playing up also. if i fill the tank right up the guage only shows 2 thirds full and then still with a third to half of a tank left its showing empty with the petrol warning light on! anyone got any ideas if this matches the what seems to be quite common problem of fuel pump noise!?!?!
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Simon, There may be problems with your fuel tank vent - the hissing would be air entering the tank (thus no fumes on the outside). When you hear the "gurgling" noise, if you open the filler cap does the noise stop immediately? Also, are you sure that the tank is full, or is it just when the trigger on the nozzle clicks off (too much backpressure - fuel tank vent not working properly). The change in pitch of the pump may be the change in system voltage due to the brake lights, as the pump slows down. The noise may not start up immediately because the pump is not operating in a vacuum (tank at atmospheric pressure), but as the pressure drops the pump has to work harder. Cheers! Steve Sears 1987 Audi 5kTQ - occasionally with loud "bees" in the tank 1980 Audi 5k - quiet "bees" on passenger side 1962 and '64 Auto Union DKW Junior deLuxes - engine sounds like a bee (SPAM Blocker NOTE: Remove SHOES to reply)

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Steve
Thanks for that, 40 to the local garage later and they have sorted it! you were spot on! much appreciated!
Regards Simon
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