Tuning I Need some help understanding multi-pumps and reservoirs

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Milehighguy

Member
Feb 11, 2022
19
2
CO, United States
All,

I have a problem with a multi-pump that I can't seem to fix. Perhaps some of my story and the issues I'm seeing have been experienced by one of you and you can lead me in the right direction.

I have a .25 Seneca Aspen. After about 1000 shots the pump started getting really hard to pump and eventually was nearly impossible. So, I started doing research and found out this is a fairly common Aspen problem and the solution is to change the seal on the pump rod. Ok, no problem, I found a video of a guy (Big J.) who had a video walkthrough of the required process to disassemble the Aspen and install two -006 o-rings. So, I got the Aspen apart and ran into an issue. My aspen has a brass nut holding the pump rod in and it takes a specialized tool to remove. No problem, I improvised a tool and got the nut out (after two days). I then proceeded to replace the seal with the o-rings. While the Aspen was apart I made sure every thing moved like it was supposed to. I then carefully reassembled everything for testing.

Once back together I tried pumping the Aspen up. Unfortunately no matter how much I pump I get no pressure, no air into the air reservoir. After fiddling around for a bit I noticed that the pump was indeed pumping but the air was escaping out the barrel and not going into the reservoir. It reminded me of when I first received my Gauntlet. I had to use my buddy bottle to fill the reservoir the first time as the valve wouldn't open using a hand pump. So, I used my buddy bottle and sure enough I was able to fill the Aspen. However, with the reservoir filled the pump handle is impossible to move. It's like a vacuum is created when the reservoir has air in it and the more air it has the stronger that vacuum is. Also, the Aspen is not holding air. It takes about an hour to lose the full air charge, that's new. After five diss and re-assemblies of the Aspen I'm no closer than I was when I started.

So... anybody see a situation where when utilizing your multi-pump's pump the air simply goes out the barrel? How about a situation where, when the air reservoir is full you can't utilize the pump? How about, you work on your multi-pump's pump and now the reservoir wan't hold air?

To be clear, I never messed with the valve.

Any help or direction would be greatly appreciated.




 
I dont have experience with the aspen but I do have experience with resealing pcp airguns. It seems like there may be more than one problem here. I suspect that your gun was degassed for too long and that the seals in your valve may have gotten misshapen. Generally if I degass a gun I change all the orings or I refill within 10 or 15 mins to prevent this from happening. Im sorry but I don't have any clue about why the pump may be freezing or not pumping but I suspect changing the seals in the valve might stop the air coming out of your barrel. 
 
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I don't know anything about your particular gun. However I do know airguns and pneumatic, hydraulic pressure systems.

2 things. Hammer has to be cocked to pump from empty. Without chamber pressure hammer resting on valve may keep it cracked open. Air will go down barrel. Vacuum when pumping implies check valve that let atmosphere air in to be compressed is stuck closed. There have to be 2 check valves in a pump, 1 to let air in and prevent it escaping, 1 let air leave to high pressure side and not go back into pump chamber. The input one is stuck closed.

I hope this helps.
 
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As I understand your description, you replaced the pump rod seal. The original problem would not have been that but would have been the high pressure and mid pressure check valves. These were known to burn if pumping many strokes in a row over many uses. It sounds like you've created new problems along the way. 

I have helped disassemble one of these but honestly cannot remember the details. To me, it's just a multistage pump attached to a pcp, and I would approach it from that perspective . I would COMPLETELY disassemble it and inspect every valve seat and seal and clean/polish all of it before reassembly. Once it works correctly, avoid a bunch of back to back high power shots and pumping, if possible. Heat is the enemy here.

It seems that someone came up with better valve materials but I've not followed it closely so I wish you good luck. They are a pretty decent rifle overall .

Bob
 
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