I will use my compressor to blow more air into the line going to the tank to see if that helps...Will report back
With it all hooked back up, line out of pump into a pan, pump on, seal off the gas filler and blow compressor air in there( flat rubber with small hole). If you can get to the rollover vented line plug it. This should force enough gas up to the pump to get it started. Also as said, put more gas in it, this will raise the level in the pick up tube.
We work on lots of big rigs that drivers run out of fuel. Some Have no primer pumps and this is one of the only ways to get them started.