Newbie question regarding fuel pump noise (85Q Coupe Quattro)

[Huw Powell]

> When listening to my recently acquired typ85 Coupe Quattro while it's
> idling, there's a distinctive high-pitched sound, which can be clearly heard
> near the rear left hand wheel. Some sort of a "whizzzzzz" - well, add some
> white noise to a sawtooth wave - with a constant rate, unchanged when the
> engine revs occasionally fluctuate. The exhaust system doesn't have leaks.
> This would suggest the noise is emitted by the fuel pump (out-of-tank,
> right?). Is this supposed to be normal, or should I spare some money for a
> new unit? I have no idea if and when the pump's been replaced.

It is the fuel pump.  If you can't hear it in the car with the engine
running, don't worry.  If its hard to mask with the radio, might want to
start shopping for a fuel pump - but even when loud they can last for
ages.

There are three parts all clamped and rubber bushed together on the
"fuel tray" which is rubber bush mounted to the floor pan.  The parts
are the pump, filter and accumulator.  There is a pre-filter in the hose
from the fule tank.  Crawl under and take a look at it, many of the
rubber bushings die and are "repaired" with zip ties, clothesline, rags,
etc.  That can make the noise louder sometimes.  There are also two hard
plastic fuel lines connecting the three parts, the degree of rust on the
fittings (and on the accumulator) will determine how prepared you should
be to replace them as well.

There is a rubber gasket thing in the floor pan where the main hose
comes out of the tank - make sure it is intact, since tank rust can
start if salt/sand/water can get up through it.

--
Huw Powell

http://www.humanspeakers.com/audi/

http://www.humanthoughts.org/