If a pump/engine unit, it should always be stored in an upright position. For short storage time frames (up to 3 months) a fuel stabilizer should be added to the engines fuel and spray a light coat of WD40 inside the pump intake and in any ports on the pump. If the pump will be stored in a region where it may freeze, a biodegradable anti-freeze such as Amsoil Low-Toxicity Antifreeze and Engine Coolant should be poured through the pump and added to the engines radiator, if equipped, to the manufactures specified water to coolant ratio. If storage is to be longer than 3 months, then the engine should be run completely out of fuel before storing and spray the inside of the pump with a long term corrosion inhibitor such as WD-40 Long-Term Corrosion Inhibitor.
If a pump end only, the inside of the pump should be lightly sprayed with WD-40 Long-Term corrosion inhibitor and stored with the pump inlet down. Do not get the inhibitor on the pump mechanical seal.