I deadhead the fuel line into the gauge, and idle the engine for half a minute on the fuel in the float bowl. If you can't idle that long on the gas in the carb, fix the carburetor. A fuel pump test has three steps- - - -volume, pressure, and vacuum. 30 seconds at idle should pump at least a pint of gas into a catch container. Idle pressure should be 3-4 PSI, and the pressure should stay there for at least a few seconds after shutdown (tests the output check valve). Check the vacuum on the input side- - - -it should be at least 12-15 inches of mercury, and it should also stay there after shutdown. (tests the inlet check valve). Failing any or all of these tests means you need a rebuild or a replacement pump. Passing the pressure and vacuum tests with low volume means there's a restriction or an air leak between the pump and the gas tank. The flex line between the engine and the frame should also be vacuum checked- - - - -some of them are prone to get pin hole air leaks.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!