[s-cars] 95 A6 non-start

[Dave Forgie]

Elvis:  If you haven't already figured it out, I would put my money on the fuel pump.
Sounds like it is getting old and weak and only likes to work when the tank is more than half full. 
Could be a loose connection though because moving the car seems to shake some thing up.  
The fuel pump is pretty easy to change, IF you get the tank down to there is less than 15 L (4 US gal) left in the tank.
See the UrS4 fuel pump DIY I wrote up some time ago (A6 avant should be the same):

http://www.elektro.com/~audi/fuelpump/

Dave F.