Onan 4000 just shuts down on load No tripped breakers

We've checked what we know and find nothing amiss that's obvious. But if we have the microwave and a 1200 watt hair dryer going and the AC kicks on, the generator just stops. But no circuit breakers ever trip. I find nothing in the manual that says the generator just shuts down by itself if 20 to 25 amps are being drawn. I wonder if a fuel filter could be constricted just enough that when the governor calls for full throttle, it starves for gas. Do you think that's a possibility?