If the engine won't idle for 30 seconds on the fuel in the float bowl, fix the carburetor, or whatever else is wrong. Just disconnect the fuel line and put it into the catch container. For the pressure and vacuum test, just refill the float bowl through the vent tube with a turkey baster.
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!