Need help with my Gehman hand pump

[seamaster]

My Gehman hand pump is unusable now.

After 4-5 pumps, it becomes a suction. Progressively harder to pull up. Then it becomes impossible to pull up.

Hand pump is very hot to touch.

When I turn my air cylinder, open up the bleeding valve, the hand pump actually pops back up.

What seems to be the problem?

[kevinweiho]

My Gehman hand pump is unusable now.

After 4-5 pumps, it becomes a suction. Progressively harder to pull up. Then it becomes impossible to pull up.

Hand pump is very hot to touch.

When I turn my air cylinder, open up the bleeding valve, the hand pump actually pops back up.

What seems to be the problem?

Seems like you have to change the seals on the pump. The Gehman pump is actually a FX 3 stage pump...

[seamaster]

http://www.pilkguns.com/air-rifle-seal-replacement.pdf

This is a Hill Pump diagram, but close to a FX 3 diagram.

Where is the high pressure seal? (feels like pressure sucking handle)

[taz]

Maybe this thread will be of some help.

http://talonairgun.com/forum/viewtopic.php?p=17559

Further down you will find a diagram of the pump.

[kevinweiho]

seamaster wrote:

Where is the high pressure seal? (feels like pressure sucking handle)

The cause of the pressure sucking the handle is a deteoriated check valve seal or the seal in the inner compression tube...

This link shows how to diassemble an older version of the FX (more like the new 4 stage pump).


http://www.network54.com/Forum/79537/th ... n+my+Pumps

[seamaster]

Spent a full vacation day working on this pump. Took apart this hand pump and putting it together by picture and by chance.

Finally come to the conclusion the problem is the inner hydraulic pipe valve.

I was able to take apart the outer tube from the inner tube. Checked the bottom assembly. But there is one inner most part I can't get to.

I can't take apart the hydraulic pipe from the inner tube.

On step 3 of Kevin's weblink. How did he took the piston off the inner tube to reveal the innermost hydraulic pipe?

I don't think it is screwed on, there is no screw thread. I tried to clamp and pull it off. No go.

How do I get the attached top and bottom piece off the inner tube to reveal the innermost tube/valves?

[Volker]

I don't know if this will help you but here is a link to a German message board talking about taking a Gehmann hand pump apart. Maybe the pictures will help and/or you could run it through Google Translate. I can also help to translate pieces but I need to warn you that I'm new to shooting and have never even used one of these pumps :)

http://www.co2air.de/wbb3/index.php?pag ... adid=25090

[kevinweiho]

seamaster wrote:

On step 3 of Kevin's weblink. How did he took the piston off the inner tube to reveal the innermost hydraulic pipe?

I don't think it is screwed on, there is no screw thread. I tried to clamp and pull it off. No go.

How do I get the attached top and bottom piece off the inner tube to reveal the innermost tube/valves?

Robert (the guy who disassembled the pump) viced up the base, grabbed the tube with both hands, gave a grunt, and it unscrewed. Any tighter and he'd have had to use a strap wrench.

I believe that you have to unscrew the tube from the base and then you'll have access to the innermost hydraulic pipe.

[luftskytter]

In the German thread that's linked above, the text in the drawing is in Swedish. And this means that the Gehmann pump is made by FX.
I know cause I've got one; swapped it second hand with an identical pump marked FX to get the right fittings......

[seamaster]

http://www.google.com/imgres?imgurl=htt ... CBoQ9QEwBA

Good grief ! I now understand how this pump thing works.

Now I just need to get to the third chamber. How do I take those two upper end piston and lower end piece off?

Kevin, do I really just pull with brute force as you describe? ?? It does not seem to work so far.

There got to be an easier way to get to the third chamber.