gazoome wrote:
As you can see in the photo, there is no cap or any adjustment mechanism on the valve extender.
The tube/tire has a normal presta valve on it (you cannot see it right now). If you are familiar with a presta valve, it just has a little hand operated nut on the top. This opens and closes the valve. You unscrew it prior to pumping and then screw it down tight after pumping. When it is unscrewed, the valve is open. If you were to press on the valve you would let air out. When the nut is screwed down, the valve is closed and pressing on the valve would not let air out.
What you have is a zipp valve extender screwed onto your presta valve. The zipp valve extender is essentially a straw that screws on top of the presta valve. This extender however makes the presta valve inaccessible (it is in the middle of your rim anyway which is why you need the extender). Because you cannot access the presta valve and the nut on the top of it, when installing the zipp valve extender, the valve is left open. This is fine because nothing can bump it causing the valve to leak air. When you pump air into the zipp extender, the air pressure pushes the open valve down and the air flows into the tube. When you stop pumping, the air in the tube pushes the valve closed retaining the air in the tube.
It does not seem like you have any issues right now. You put your presta pump on the zipp valve extender, pump away, and air is going to the tube. If this is the case, great, keep doing what you are doing. What others have speculated is that the little nut on top of the presta valve "jiggled" closed. This can happen while riding over time. This is a problem because once it closes the only way to open it is to remove the tire/tube, remove the zipp valve extender, and re-open it.
I do not use this type of extender. I recommend the removable valve core type extender where you take out the valve core (the part with the little hand operated nut that opens and closes the valve), add a different type of extender, and reinstall the valve core on top of the extender. For this you would need a new extender and a tube with a removable valve ccore. With the zipp valve extender you have, I believe the recommendation is to essentially break the valve core open. You do this with a plyers by over unscrewing the little nut on the top till you hear it click. In doing so you will have essentially stripped the nut to a permanent open position. I have never done this so take that with a grain of salt. For all you know, this was done when the extender was initially installed.
Regardless, if air is going to the tube right now, there is no reason for you to make any changes. Pump the tube and enjoy your ride!