Hi Joe,
I saw your picture. It looks like someone added that valve to the gas line for the purpose of... siphon maybe? Who knows. It's not a stock item.
I don't see how it would help drain as the pickup line goes through the top of the sender. I wouldn't assume yet that the gas is drained out of the tank... you didn't say how full the tank originally was.
The Sender should have this rigid line coming out of it and going between the tank and back of the cab where it connects to a hose with fittings. The hose passes through a hole in the cab floor. The metal gas line runs down the frame from the carb and connects to the other end of the hose.
I will tell you that I had trouble with my sender in that the screen was totally clogged and wouldn't pick up any gas. I pulled the sender and cleaned it out and it worked fine. New Senders are under $30 BTW.
As for the pump, the pump lever does contact a lobe on the cam. As mentioned these lobes can wear, affecting the performance of the pump. Since you tested the pump with a can and the engine ran fine, I think we can rule out the pump.
I really would check the pickup screen on the sender.
Also, the two wires are for your gas gage. One, connected to one of the screws attaching the sender, is a ground wire. The other is for the gage.
Hope this helps. Good luck and keep us posted!
Jerry
