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Sm3k Help

pump leak?

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#1 cheyner

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Posted 28 May 2010 - 10:05 PM

So, I'm almost done my Sm3k and I'm down to one problem. Either my pump is leaking because they didnt put enough plastic on it, the OPRV is out of whack, or I am actually filling the tank on one pump. Does any of this make sence to anybody?
Posted Image
Should I plug this hole?
Or should I plug my OPRV?
I replaced the o-ring with a new one, does this grant me magical one-pump powers? Is somebody going to sig what I just wrote?
It's a yellow Sm3k, and I have never fired a working Sm3k to compare the air-output to.
Help? Suggestions?
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#2 jaybo1996

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Posted 28 May 2010 - 10:25 PM

Pumps are designed so that when you push fowards, friction pushes the O-Ring back into postition, and it makes a seal, but when you pull back, friction pulls it foward, making a terrrible seal and therefore letting air enter the pump shaft to pumped inside the tank with the next stroke. When you replaced the O-Ring, you may have messed up this mechanism, and made your gun only able to pump once, then have a vaccume inside the pump shaft after the first pump.

Edited by jaybo1996, 28 May 2010 - 10:26 PM.

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#3 Blue

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Posted 28 May 2010 - 10:40 PM

Yeah, go back to the stock one. If it doesn't seal, you can put on silicone grease and maybe layers of teflon tape under the o-ring. I don't get what your pic is showing though.
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#4 cheyner

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Posted 28 May 2010 - 11:46 PM

If there was a vaccume effect, I would not be able to pump it more than once without quite some effort. I can hear the air rushing into the pump tube as I pull the pump shaft out.
This testing is all being done with the internals in my hand, when I plug the hole in my picture with my finger it becomes pretty hard to pump in, but easy to pull back out.
The problem is the air coming out of the pump shaft, is this the OPRV kicking in? There is a half decent pop when I pull the pin on the tank, but I have never used a Sm3k before so I have no idea if this is normal.
Is it possible that I am indeed filling the tank with one full pump?
Or, because it is a old ass yellow Sm3k, could the OPRV have weakened?
Should I just plug the OPRV, or apparently for future refrence, the pump shaft?
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#5 imaseoulman

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Posted 29 May 2010 - 11:21 AM

The hole is in the end of the pump that attaches to the pump handle, so it is not effecting pump efficiency. If you lost the original o-ring, you can drill a small hole in the pump tube to allow air to return back in.
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#6 cheyner

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Posted 29 May 2010 - 04:00 PM

The hole is in the end of the pump that attaches to the pump handle, so it is not effecting pump efficiency.


Thank you, one down.

Ok, still, not a vaccume issue. The leak was the same with the original o-ring, with the new one it just happens faster, this is what is leading me to belive that the OPRV has weakened over time.
I know that if water got in there it could have rusted a bit and that would have weakened it a bit.
I am going to rip apart my green Sm3k and try the pump shaft from that.
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#7 moosa

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Posted 30 May 2010 - 10:11 PM

I believe that stock SM3K's usually fill in about 2 pumps before the OPRV kicks in, if that's any help to you. There's generally some variation in that it might take slightly more or less than two full pumps before you can hear the valve release. I think your idea of the valve possibly just needing to be adjusted is a sound one.
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Yes.

#8 balisticjoe

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Posted 30 May 2010 - 10:33 PM

The problem you are describing sounds similar to one i had with a big blast. Unless I misinterpreted it, it seems like the check valve in the pump is leaking. If you hold the pump handle in the tube and you feel the air pushing back slowly, that is probably the case.
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#9 cheyner

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Posted 31 May 2010 - 08:25 AM

Thanks for the help everybody, I plugged the pump and called it a day.
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