Discovery Pump-air comes out intake on downstroke
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Discovery Pump-air comes out intake on downstroke
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Topic: Discovery Pump-air comes out intake on downstroke (Read 2914 times))
Franklink
Sharp Shooter
Posts: 802
yes
Discovery Pump-air comes out intake on downstroke
«
on:
October 19, 2014, 04:43:10 AM »
As stated in the title, on upstroke air enters in through the intake as it should. On the downstroke, air comes back out the intake, as it shouldn't. Air will not come out the hose. I have opened the pump and replaced every oring and still the same problem. I have reopened the pump and tried more lube-same problem. Reopened the pump and tried less lube-same problem. (lube=silicone oil)
I cannot find any corrosion, bent shafts, bullet holes, flattened by a semi running over it parts, etc. that would indicate ruined pump. The blasted thing just wont pump any air-even with brand new seals.
I have removed the hose to make sure it is not plugged. It is not plugged.
I thought, well maybe the little ball check valve is sticking. It will bounce around in its housing without any inclination that it would like to stick. When removed from housing for inspection it appears as pristine as when it was new.
Air simply does not appear to be getting into that third stage.
Odd thing is that when the handle is removed I can pump by holding onto the thinnest inner shaft and the outermost shaft with the Benjamin logo and get air pumping out the hose. This is not a viable option for high pressure and I doubt I could hold onto everything once the pressure builds higher than a few pumps. When the handle is screwed in place and the pump is pumped-same problem, air out the intake on downstroke.
I hear the small oring on the smallest shaft is a common problem. I have the white "upgraded" oring from sunoptics in that location and have replaced it with regular black orings of differing hardness in attempt to diagnose-same problem.
This pump has not been abused. When it was working it pumped up two pcps, no more than 50 strokes at a time ever, one 100cc air chamber volume gun to 1800 (yeah about thirty pumps from 1000 to 1800) and the other a discovery-2000psi (fifty pumps from 1100 to 2000).
If you know of a solution or have an idea of another place for me to look, please post away.
Thanks in advance.
(If no solutions, what would be a fair price to ask for a non-functioning one-owner Discovery Pump with enough new orings to replace every one on the pump over thirty times and the dessicant dryer from Sunoptics? ha ha)
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Arizona
nervoustrigger
GTA Senior Contributor
Posts: 8701
The Grin Reaper
Real Name: Jason
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #1 on:
October 20, 2014, 06:28:58 PM »
It's a long shot but I had this problem once, at least I think that was the symptom.
It was simply that the 2nd tube (the one revealed when you pull up the handle) had become loose. Apparently this tube would cant slightly on the downstroke, allowing air from the 2nd stage to bypass the O-rings on this tube's ID and back into the first stage and out the inlet. That's how I remember it anyway
To fix it, all I had to do was put a wrench on the brass fittings at each end of the tube and tighten them up well. Basically putting an axial squeeze on the tube.
Ther fact you've been back in and reassembled makes me think the problem is elsewhere. It would have jumped out at you I think. So like John, I am suspicious of the ball check or its seat.
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MS
Conduct yourself so that when a man accuses you of something dishonorable, no one will believe him.
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Franklink
Sharp Shooter
Posts: 802
yes
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #2 on:
October 21, 2014, 01:01:37 AM »
Thanks for the ideas. I'll inspect the ball check valve more closely.
The loose second tube idea makes sense since I only hand tighten that one. It was such a bear to break free the very first time I got into the pump that I have been very careful to not overtighten it- maybe it needs a little more squeeze on it for those oringa to seal as you found with your pump.
Can't tell you how much I appreciate the suggestions-I'll report back so that some poor soul in the future can maybe benefit from this.
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Arizona
nervoustrigger
GTA Senior Contributor
Posts: 8701
The Grin Reaper
Real Name: Jason
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #3 on:
October 21, 2014, 03:24:37 PM »
Yeah, the second tube is pretty tough to break free the first time. I had only hand-tightened it when I reassembled and it worked loose after about 20 pumping sessions. When I got to looking, it was noticeable without disassembling. I could extend the outer tube and grab the second tube and spin it by hand.
But just for the benefit of anyone else who may be reading, really cranking down does not do anything to improve the O-rings' ability to seal against the tube (i.e. does not compress the O-rings). As soon as the parts are snug, the important surfaces should be nice and parallel and concentric which gives the O-rings the best opportunity to form a good seal. The problem occurs when the parts have unthreaded enough that the sealing surfaces begin to shift during pumping. Getting things good and tight just puts some preload on the threads to keep the parts from unthreading. Some threadlocker would achieve the same thing but I would not recommend its use here; that stuff is pretty caustic to some materials so I would not risk it without explicit knowledge of how it affects O-rings (Buna-N, Viton, polyurethane, etc.). Plus it cures to a hard crust-like consistency so if any broke free, I doubt it would be good for the O-rings.
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MS
Conduct yourself so that when a man accuses you of something dishonorable, no one will believe him.
Barrel accurizing guide
My youtube channel
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Franklink
Sharp Shooter
Posts: 802
yes
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #4 on:
October 22, 2014, 06:21:43 PM »
Last night I had a chance to look at the pump some more. I initially focused on the check valve-it looks perfect, no nicks, no debris where it seats. No visible problems there.
I then tried to snug up the tubes as suggested. I didn't go crazy and get out the cheater bar to really get leverage, just snugged them up with a wrench to the point that I knew I would be able to get in the pump again WHEN necessary. No dice, still the same problem of not building pressure and air escaping out the intake on the downstroke.
So, I thought maybe one of the orings is nicked or damaged and I just havent seen it. Replaced EVERY oring AGAIN. Put it back together and same exact problem of not building pressure and air out the intake on downstroke.
Any more suggestions?
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Arizona
Sfttailrdr46
Beginning the next chapter
GTA Senior Contributor
Posts: 16153
Me at Devils Tower Wyoming 8-13-2000
Real Name: Don
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #5 on:
October 22, 2014, 06:29:03 PM »
If you can order an entire check valve and not too costly maybe try that or use as a garden ornament unless still under warranty then send in for repairs and ask for any replaced parts be returned to you with explanation of what was wrong
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Mesa Arizona
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nervoustrigger
GTA Senior Contributor
Posts: 8701
The Grin Reaper
Real Name: Jason
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #6 on:
October 22, 2014, 07:35:29 PM »
Well, sorry to hear it. Might be time to call Duane at Sun Optics and explain the symptom and what all you've tried. He either designed or was involved in the design of the pump.
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MS
Conduct yourself so that when a man accuses you of something dishonorable, no one will believe him.
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caniborrowsomeammo
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Marksman
Posts: 379
U betcha
Real Name: John
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #7 on:
October 24, 2014, 02:01:13 AM »
There are 2 check valve/balls in the pump P-18 and P-37.
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SANTA ROSA, CA
Daisy Red Ryder-
up to and including:
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and a buncha other darkside stuff
Now .30 Flex, what a shooter this one is.
Franklink
Sharp Shooter
Posts: 802
yes
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #8 on:
October 24, 2014, 02:53:46 AM »
P18 is the metal cone shaped chefk valve upon which an oring, p,19, resides. P19 has been replaced and p 38 (the ball check valve) has been inspected and has no visible damage, nicks, abrasions, ect.
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Arizona
Franklink
Sharp Shooter
Posts: 802
yes
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #9 on:
November 13, 2014, 02:12:25 AM »
Update:
Sent it in to Sun Optics and asked for a note with the diagnosis. The pump came back today and works fine. The note is from a guy named Michael and said he was unable to "isolate" the problem and just replaced the entire pump base. Sun Optics provides great customer service.
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Arizona
woogie_man
silence is golden,and not illegal
Expert
Posts: 1800
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #10 on:
November 16, 2014, 05:42:17 PM »
Wonder if the hole that goes from the pump to the house was blocked our crimped shut for some reason?
At least you have it fixed now
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North Dakota
shorty
Expert
Posts: 1936
yes
Real Name: Tim
Re: Discovery Pump-air comes out intake on downstroke
«
Reply #11 on:
November 25, 2014, 06:00:15 PM »
There's a hidden Oring (hidden if you don't read the parts diagram) that the high compression piston rod rides on. It is #3 or dash number 107. A couple flat plastic washers hold in in place. I have found that this oring will allow air to be taken in from the pump but when you compress the pump, any shift in the (crooked) main high pressure piston rod will allow all the air to back up into the system not providing any compression.
Took a while to figure it out but appears to fix my POS benji pump. I hate that pump so much that I can't stop trying to repair it just to shoot without buying another pump.
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Palm Coast, FL
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Discovery Pump-air comes out intake on downstroke