FoggyB5

I'm working through a EVAP system trouble shoot on my 2002 S4.

The symptom is related to the pressure in the gas tank. The gas pump thinks my tank is full when it's not. So I have to put gas in one squirt
at a time. No check engine codes are triggered, however after a few weeks of this, the gas gauge also failed. First it started giving erratic readings, up down up down, until finally settling on empty.

These symptoms started after a shop replaced my fuel pump so that may be related but also maybe not.

So far I've replaced the EVAP solenoid valve and the carbon canister and neither solved the problem. I know some EVAP systems have another "carbon canister vent" but as far as I can tell that is not the case on the B5.

Any ideas what I should check next?

SCarGuy

the gauge is a single wire connection at the pump


the filling issues are either the charcoal canister itself or the vent hose that connects to it

FoggyB5

Thanks, I'll check the vent tube because I've already replaced the canister.

I guess I could hit it with compressed air to make sure it's not clogged. Would that mess anything up?

I think the vent is the top hose. The other two
are the vapor in and out (one wider one narrower diameter), right?

FoggyB5

Also is the fail likely a clog or could a leak also cause this? If it's a vent it seem like it's probably not a vacuum line but I think some of this system is a vacuum.

Thanks again for any passed on knowledge.