Have them do a hydro flow test and see what the flow rate is on the pump. If the flow rate is let's say 8psi per min at 2200 rpm and it drops more than 4 psi at any number of flow rate wether it's 8 7 9.5 or whatever if it drops out 4psi of flow the pump is bad and needs to be replaced. If it is...
Take the fuel line off after the shut off valve then get you a jar and open the shut off it should pour out the size of your hose or appear bigger than your hose. If not take off gas cap take a bright light look down inside for grass a other stuff if gas is not coming out take an air compressor...