I think those sprayers have rubber diaphragm pump. I afraid the rubber diaphragm probably weather cracked and won't pump or plugged up. If it's the hand held small model probably not worth dumping money in. I would just buy new one. Those sprayers are hard to get clean and once any paint residue dry it's like concrete to get out of the small passages.. IF you need to paint I would just by new one with parts available. If it's the more expensive model that goes on 5 gallon buckets and have separate pump with the long hose with the hand held gun nozzle then it maybe worth trying to find of parts for it?