Check engine power switch. Low oil shut down is activated. Add oil to engine, check more frequently. Low on fuel. Fill with the appropriate fuel, bleed injector pump on diesel engines.
Fuel filter is clogged.
Replace or clean fuel filter, bleed injector pump on diesel engines. Engine flooded or starved. Engine bogs down under load, whenever spray gun is triggered. Engine needs to be repaired or replaced. See engine manual or engine dealer.