GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: teknobel on June 27, 2013, 12:56:46 AM
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I'm sure someone here will know the solution to my problem. Sorry if this isn't the correct place for the question.
I was given an old Daisy 881 a few years ago. It would only hold pressure to 3 pumps. Beyond that the valve would leak out any additional pumps. I purchased a new valve assembly and seal kit to rebuild it. The new valve assembly isn't leaking, but the new chamber seal is not sealng either. I can get one pump in, but any further pumps empties the chamber and starts from scratch. I lubed the new seal when I installed it. I don't see any nicks or deformity with the new chamber seal. Is there some trick to getting them to seal? Or should I just assume I can't see the defect and order another seal?
Suggestions?
Tom
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If you have not tried it, cock the rifle and leave breach open, then pump it up.
DT
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Thanks for the suggestion Dick, but that is my procedure. I have this problem when I do those steps.
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No problem, that is sometimes an overlooked step. The last rebuild I did was an 850 and it leaked when I was done. I dissassembled cleaned and relubed and assembled again and it worked for me. Must have missed getting a seal right, they can be picky sometimes.
DT
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Tonight I disassembled the rifle again thinking that I would re-clean and re-assemble. The process helped me identify more of what is happening. On the first compression stroke, the mechanism seems to work correctly. Then when the "pump" mechanism is withdrawn for the second compression stroke, the chamber seal is being pulled (by vacuum) or pushed (by positive air pressure) (or both) over the ridge formed in the pneumatic tube that the seal seats against.
Is there a mechanism I am missing that lets air back into the pump stroke to permit the compression pump to be withdrawn without the vacuum resistance?
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just a thought did you by chance put the valve in backwards? don't know on a daisy but a crosman pumper you can. ask me I did
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I don't believe I did it wrong. The valve is threaded on one end and can only fit one way.
I'm assuming you actually meant the chamber seal. The seal is flat on one side with a groove cut at the edge that matches with the ridge in the pneumatic tube. I believe that face should be toward the pump mechanism (on the other side of the ridge in the pneumatic tube). The other side of the seal is formed with the expandable edge of the skirt and is formed with a nubb for a spring to seat against. It seems that face should be toward the compression chamber since the valve body pushes on the other end of the spring. This orientation would permit the skirt on the seal to press/seal against the pneumatic tube within the compression chamber. The schematic diagrams seem to show the orientation I have it installed.
I appreciate the ideas so far. They are definitely helping me work through the issue. Please keep them coming.
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Seems odd. I would think that the ridge in the pump tube would make that impossible.
Are you using the original metal face for that seal?