Correct fuel breather valve function?

[Jmattiko]

Hi

Does anybody have clear understanding of the "fuel breather valve" on a 964? This is the component that is part of the fuel vapor purge system. Part number 928 110 429 08

The electric solenoid valve is clear in that it opens when engine is fully warm and at partial throttle conditions. This is the larger diameter hose that can be traced back to the carbon canister in the rear fender well.

This hose passes thru the breather valve with the breather valve having a vacuum line attached. Have not been able to find a definitive write up on the valve inner workings.

I had thought the valve controlled the volume of air that could be drawn by the large diameter hose based on vacuum, there bywhich this unmeasured air leak could be made proportionate to air mass at a given time.

I now think he vacuum line is a permanent small diameter vent source for the carbon canister with the solenoid valve controlled large diameter hose doing the heavy lifting when engine conditions are more favorable.

Reason for my thinking is that I can not hold a vacuum on he valve and the physical dimensions look a bit small to contain a bladder and spring assembly.

Perhaps my first thought is correct and I simply have a blown valve that is letting air pass now that it is faulty.

Any knowledge out there?

Thx

Joe