Fueltank pressure..

[Carfreak]

Hi! Just wounder if it´s normal that the gastank gets alot of pressure after some driving?
When opening the fill cap I hear a loud psssss.. Don´t know if its vacuum or pressure..

Is it possible to bypass the colcanister to see if that helps and how to ?

[UrS4boy]

Hi! Just wounder if it´s normal that the gastank gets alot of pressure after some driving? When opening the fill cap I hear a loud psssss.. Don´t know if its vacuum or pressure..Is it possible to bypass the colcanister to see if that helps and how to ?

There is a check valve in the evaporative emissions system. Normally there is a vacuum on the tank, not pressure. Item 18 (PN 4A0201096) is a "bleeder valve" (one-way check valve). If it is working properly, you get a vacuum on the tank. If it fails there is the possibility of boost pressure working its way past the N80 Evaporative Emissions valve (ECU controlled), through the emissions canister to the fuel tank. Not good.

http://forums.quattroworld.com/s4s6/msgs/21014.phtml

[johne]

My car does the same from time to time, never caused any problems in 160,000 miles.

John

[Carfreak]

Ahh okey.. so vacuum in the tank is normal then.. my bleeder valve works (output test in vag-com)

[Nuno Cristiano]

And cars that not use Canister?

[QuattroFever]

My car does the same from time to time, never caused any problems in 160,000 miles.

John

Any idle problems?