What does the Fuel Tank Bleeder Valve actually do?
 

2000 Boxster S with difficulty adding fuel. Intermittent P1128 and "coke bottle" sound from the filler neck. When I trip the flapper reed switch I can hear/feel the electrical valve at the top of the fender click.

Does anyone know how to test the Fuel Tank Bleeder valve? What does it do besides being a holder for the flapper reed switch? It seems to have no solenoid or electrical component besides a ground strap.

If I disconnect the hoses from it I can fill up my tank. If I reconnect them I cannot fill up my tank. I can blow air through it, and I can blow air through the vent line that goes from it to the top of the fuel sender. If it's allowing air through it from the black fitting to the orange fitting is that normal behavior? It may be restricting the airflow some but it's hard to tell.

When I had that issue on my 2000S, replacing part you display solved it.

My only input is make sure you put the reed back where it belongs, I had to go back.

Well, I finally broke down and replaced this. It did not fix my difficulty fueling issue.

I still don't understand exactly what its function is in the system but here are my observations about what one can test to see if it functions the same as a new one. Both my original valve and the new one both behaved this way:
-Blowing (with normal human mouth pressure) from the black fitting exits the orange fitting with some restriction
-Blowing from the orange fitting exits the black fitting with slightly more restriction
-If you press the plunger that's normally depressed by the lip of the fuel cap it opens the air path up completely and one can blow either way without restriction
-Confirm that you secure the reed switch back in the little slot when reinstalling if you removed it

If you get about a 1/4" diameter piece of hose you can probably perform the above tests without removing it from the car. If you suspect a problem with this valve and it behaves as above your problem likely is elsewhere. I ended up wasting about $120 on a replacement.