Fuel Pump

[Mike & Genny <kistner@aminet.co.kr>]

Imagine my surprise to find other drivers who love thier Audis!

I'm a civilian working for the Army in Korea.  I have a '87 5000S which has
110,000 miles on it.  The local Audi dealer is good with repairs once I get
past the language barrier and cheap at $25 per hour.  The problem is the
cost of parts due to an excessive value added tax.  Fortunately the dealer
will install any parts that I bring in but that requires me to correctly
diagnose the problem and order the correct parts.

I need some advise on the latest problem:
When the fuel level is below 1/2 tank the fuel pump makes a loud cavetating
sound and the car dies.  It restarts immediately but dies again after
traveling 200-300 feet.  I did this for about three miles until I got to a
gas station. Filling the tank takes care of the problem although it has
happened a few times when the tank is on the full side but then it is
usually a single episode.  I've checked the gas gauge and it's accurate
based on the number of gallons I put in after the problem occurs.  I
installed a new fuel filter but it didn't help.  The fuel pump is suspect
but thats only a guess.  Any other ideas?

Second question:
The fuel pump has been loud during normal operations for over three years.
I had it changed prior to coming to Korea as a preventative measure on my
mechanic's advice.  Replacing the pump didn't diminish the noise and my
mechanic reasoned that it had to be a bad fuel pump isolation assembly (my
description) that contains the pump in the tank.  In the event that I do
replace the fuel pump should I replace this assembly?  

Any ideas or experience with either of these problems is appreciated.

Mike Kistner