Picked up a great floor jack at an auction -- paid like $12.50 for it It's one of the older big ones. Anyway, now it's quit working after I haven't used it in a while. There's two plugs -- one in the base and one on the "barrel" of the jack. Do you add oil to the base, then bleed air out the barrel? Everything moves, just won't lift. Might be airlock, but I can't seem to clear it. Don't want to try tearing it down if I don't have to!
That 'barrell" is the fluid reservoir, it surrounds the piston too. Remove the plug and turn the jack over and let it drain. While draining it, (or before), warm the pump body up with a propane torch, till it's really warm to the touch all over, to get the old oil to flow out. Just in case the check-valve is stuck, rap the pump body with a mallet a couple of times with the let-down screw loose,(the one you loosen to let the jack down with. Then fill with jack oil, not motor oil, warmed up. Be careful, the fumes are flammable. Sit it in the sun or by a heatlamp if your old lady won't let you use the kitchen. Fill the jack. jack it up, fill some more. Jack it all the way up. All the time don't put the plug in tight, just loose so air can pass. Jack it up and let it down a couple of times, it should work.
If it doesn't worked properly after a fluid fill, then the ram seals are probably shot. If the seals are bad it probably wasn't worth the $12.50 you paid for it.
In all likelyhood,the seals and wipers are standard sizes, and any decent hydraulics place will have them. The hard part is disassembly. So for $10 worth of parts and some clean oil, it will be good for another 10 years at least.
My boss knows of a guy out here in LA who restores old jacks. We've got three of 'em in the shop. If you can't find seals, I'm sure he's got them. We can work something out to get them, or I can get his contact info to you if you're interested. Old shop tools kick ass.