Out of gas or not?

No whoosh would indicate that you do not have a vent problem.

These are simple systems, but you do have to get your hands dirt. There are only "so many things.

1....Problems with the pickup. Is the tank dented from a wreck or dragging on something? The sender could be damaged

The sender pickup screen could be clogged with gum, rust, etc. Only way to find out is to find a gasket for it, drain the tank and pull it off

2....Don't mess with them REPLACE both suction side hoses. There's one from the tank sender to the fuel tube, and another up front from the fuel tube to the pump

3....TEST the pump. Read the manual. There's procedures in there. You need a pressure / vaccum gauge, which you should have, and which you can buy at any parts store for under 20 bucks. You'll need some sort of container to measure flow

4....Might be pinholes in the fuel tube, small enough to not leak sitting, but to let air in. The tube could also be clogged with rust. Blow it out with air.

5...Could even be problems with the carb. Get some fittings and "rig" your pressure / vacuum gauge to monitor running fuel pressure to the carb. If you see a min. of say, 3 psi and no less when the problem occurs, then it's not fuel supply.