Carb has no fuel after sitting for a day - leaks?

[hotrodf1]

I have a 66 with the 305 V-6 with a 2 barrell Stromberg carb I believe it is. WHen I let the truck sit overnight or for a couple days, it won't start. Took the air cleaner off and hit the throttle and no fuel from the acc. pump, so it seems the carb is out of fuel. Doesn't seem to help to keep cranking either. A little shot of starting fluid and off he goes

I will say the fuel level in the tank is probably 1/4 or lower, not sure if that would somehow have anything to do with it.

The carb is a rebuilt unit, installed less than 2 years ago judging by the receipts that came with the truck. There is some grungy stuff under the front of the carb, almost seems it could be leaking from there. Haven't spent a lot of time looking under there yet.

Could the fuel pump be allowing all the fuel to drain back to the tank and the fuel level in the tank helping to allow that?

Seems like I've heard some rumblings of people having trouble keeping the Strombergs sealed up. Is there some old hotrod secret trick I need to know about? Surely the flathead guys have it figured out from all those years of running them.

Any thoughts out there? It's pretty annoying to keep taking the air cleaner off and using starting fluid every day I drive this thing.