One way check valve next to vapor canister
 

Hi

The one way check valve is the green arrow in figure 1:
Pelican Porsche Tech Article - Replacing Your 996 Fuel Line Vent Valve / Bleeder Valve - Porsche 911 Carrera & 986 Boxster - Porsche 996 Carrera (1998-2005)

I have a fuel evaporator problem and attempted to fix it myself. I took apart the vapor canister and tested all the components. I noticed that the one way check valve allows me to blow air into both sides without any resistance. I then tried blowing air into the valve with an air compressor and I still found no resistance. I hovered my hand to other side of the valve and felt air.

Before I spend any money on a new check valve, I want to know if this is normal? How much resistance should I feel in the one way check valve? Should it completely stop air flow in one direction?