Mike

You really don't see flow because the can is connected to the same line and provides an air bleed system to push the fuel through, there is allot of air and only a small amount of fuel.

If you have doubts just pop the line off going into the gearbox, clamp the main fuel line closed and run the pump in prime mode. You should see a small dribble of fuel that has come via the needle restictor/final filter.