[bugeye]

My tractors are different, but maybe similar.

I have had the problem you described. Fuel starvation under load or when on a slope.

If the fuel tank is full and the cap vented and the fuel system clean and pump working, the engine should run unless an electrical spark problem. When the engine will not start, disconnect fuel tube from the carburetor and crank engine. Capture fuel pumped in a container. Think safety with gas around a hot engine. Fuel should flow as engine is cranked.

I changed the fuel pump with a generic sourced on evil pay or amazon. When I took apart the old fuel pump, the rubber diaphragm check valves were shot with wear.

Also check for debris in the fuel tank shutoff valves.