RWS Pump problem

[air-tech]

Hello again all, been a while... and so has usage of my RWS pump.

Basically, I can start to pump, but within a couple of strokes, when pressure builds, it becomes impossible (ever harder) to lift the handle. It just sucks down, in reality I would say that the downstroke pressure is leaking to the top part of the piston thus pushing it down.

I don't wish to take it apart any further than necessary so if anyone can advise which part, presumably some o-ring, I need to replace, and where it is found, that would be great.

Thanks in advance.

[rapidresponse1]

im sure there is a thread on you tube about these bud

[air-tech]

Seem to be about the FX mostly, and there are differences which may be important? Mine seems to be older.

[WILBA]

Sounds like the seals are going. Mine is doing the same. I will reseal it when i get a chance to.

[angrybear]

The up stroke is to suck in fresh air to each stage, if it's sucking the handle down it means you're creating a vacuum in one of the stages so one of the inlets is stuck closed.
You should be able to hear the first stage sucking in as you lift the handle.

[Shed tuner]

just strip and and replace all the o-rings... once you are that far in, may as well do the lot.

[air-tech]

Got it all in bits. After careful consideration of how the thing works, suspect the exhaust / non return final valve, as if that fails there would be a buildup in pressure that would create just the sort of pulldown I am experiencing. The o-ring is rock hard. I hope they are not particularly special ones. The tiny 3rd stage o-ring is also like rock. The others seem fairly run of the mill and are quite supple and should prove easy to replace.

[averageplinker]

Seal kits available on that well known auction site.