Pumping the diesel will not do anything as there is no pump on the accelerator. Diesels always start at full throttle and when they start the governor takes over and brings the engine back to idle rpm. If the diesel is hard to start then there is an indication that the GLO- plugs are not working. Check out their operation and check out the relay that turns them on. They are small heater elements that are in the cylinders to assist the air temperature to get hot enough to ignite the atomised fuel being sprayed into the cylinders. If you do not know of these plugs then have a qualified mechanic with diesel experience show you or have him fix them for you.