one possible way to determine if it is a fuel problem would be to disconnect fuel hose from lp tank, then remove air intake hose from top of carburetour( usually held down by 2 bolts, then manually spray carb cleaner into carb in small 2 sec bursts. if it runs as long as you feed fuel it is a fuel problem, if not at least you eliminated one possibility for your problem. Also if this unit has a points style ignition system, check points gap(.017) it can also give symptoms similar to fuel system failure. I did not intend to bash or degrade your service tech, However if you understand the theory of a internal combustion engine it should be able to resolve issue. Also I would check voltage to Ignition coil and B- with keyswitch on and after released back to run position.GOOD LUCK