Looks like you are starving for fuel.
Did you replace the rubber fuel lines lately? Ethanol in today's gas really eats up old fuel lines from the inside out.
Fuel pump? Cheap and easy to change.
Leaks in any fuel lines? Connections where they clamp to the steel lines are a common area.You will suck air instead of fuel.
Rusted pin holes in the steel lines?
Long enough pickup tube on the new sending unit?
Plugged vent tubes?? Remove the gas cap to see if you hear it suck in air.