This engine has a pull start no electric. When checking fuel pump operation, pumping bulb pumps fuel through fuel pump to carb. When I pull on rope several times nothing comes out, although when running motor continues to run so fuel pump is working, at least when motor is turning faster than pulling rope. I just put in new diaphram and gasgets and fuel pump reeds because of this but it is still the same. Is this normal that fuel pump doesn't pump fuel with just rope pulls? Could this be why motor doesn't run the way is should?