2005 A4 fuel gauge does not register Full

[bleumouton]

Need some help...

Just bought an 05 Avant... when filling gas tank fuel gauge only moves up to a point between 3/4 and 1/2 full when gas pump stops. Amount of fuel is only 7.9 gallons despite the fact it should hold 16 gals+. I've looked at the Sender unit threads here on audizine, as well as the Carbon Canister filter thread. I'm not sure which direction to go....when the fuel gauge goes down to empty and the warning light goes on I'm assuming the tank is definitely empty so it would seem the sender is working correctly. The problem seems to be the tank not accepting any amount of fuel past the 7.9 gals...so would it be the canister?

Thanks!

[customa4]

Here's some info on the system.

Here's a tutorial on how the tank evap system works. It's for a VW but the basics are the same for the Audi A4. It's well worth the ½ hour spent watching it to get a better understanding as to how it all works.

Also, here's the thread where there's some discussion on a similar problem where this quote was taken from. Click