Runs for a couple minits then shuts down? Mine did that last year. Turns out there was a crack in the fuel line between the gas pump and the genny. The pump (in mine, anyway) works off suction. The fuel line, being cracked (due to age or ethanol or both) let the genny pump suck air. Not gas. Got lucky, was able to replace the fuel line without taking down the tank.
Test: get a cam of gas, run a fuel line from the can of gas to your genny. If it starts and runs....the fuel line is the problem.
Rubber fuel hoses come in 2 versions. Ethanol resistant (about $4/foot) and standard (about $1.50/foot). Might be a sales ploy, but y'gotta go for the resistance hose.
g'luck!