What kind of things would keep gas out of my carb?

I have on order a weber but until then, whay would keep gas out of my carb? Looks like all new lines ran on the car. I installed a new fuel filter. What size lines should run on these components?filter to pump to carby? Sometimes there will be gas and it will run great for a few miles then the gas disapears and the car just turnsover but never sucks the gas into the carb......The glass is empty

Again, I know the carb does not suck gas it sucks ass. That's why a weber is on the way....but, until then????