Inexpensive Chinese Pump Question Please

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Ponz

Member
Apr 4, 2022
107
20
Missouri, United States
Bought a cheap Chinese pump from Amazon. It pumps when tested with the plug. Rifle arrives tomorrow.

While testing with supplied plug it pumps up to any desired pressure but wants to come back up a couple to a few inches at higher pressures. Is this normal?

In other words, the handle fights back on the down stroke!?! The higher the pressure the higher the pump handle comes back up.

I can't think of a more eloquent way to phrase this.

John
 
Probably fine, there will be a check valve in the airgun so the most you would lose due to the handle pushing back up is the amount in the pump/hose system. I have a cheap one and an expensive Benjamin pump, both work but the Benjamin takes fewer pumps than the cheap pump. To go along with that the Benjamin is also harder to pump at high pressure than the cheap pump. But both do their jobs and the cheap one has folding feet so easier to bring with me.
 
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THanks.

On another note: This pump is supposed to filled with a coolant according to the enclosed destruction sheet. However, one reviewer posted this:

Interesting...I posted the question on Amazon asking if the pump had water in it. The seller promptly responded and said the pump is indeed water cooled, but due to shipping limitations it does not come with water in it, and “you may add water to it on your end”. 

So - should I take it apart to check? If there's no coolant, should I add some?

John
 
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I agree, some pumps do that and work fine, and continue to work fine for a long time.


If it were pushing way up, the check valve would be suspect number one. It’s one of the easiest seals to access, just unthread the tube assembly from the base and it is right at the bottom end of the tube. A little spring-loaded seal. Most pumps include a spare in the seal kit.
 
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I also have one of the cheapie chinese hand pumps. The check valve at the bottom of the pump tube is the weak point and mine often leaks. Unscrew the pump body from the base, and at the very bottom of the pump body will be a small threaded cap. Behind that cap is a spring, check valve w/ oring. Look closely at that o-ring and see if it has any spots that look like they've been ablated. If you see any damage, replace that o-ring with one that came in the spare parts kit that shipped with your pump (hopefully). I go through these o-rings fairly quickly, each one lasts about 5 fills on my pump. I ordered bulk replacements from amazon for cheap.



https://www.amazon.com/dp/B015O321K4?psc=1&ref=ppx_yo2ov_dt_b_product_details



These are slightly bigger than the original but work just fine in both the check valve and on the high-pressure piston inside the pump.

If you put water in the pump, it will help your orings live longer since they don't get quite as hot. I learned that the hard way.
 
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Ponz,

My cheapo Chinese pump got so hot it finally blew an "O" Ring. Carefully following a recommended procedure of 40 pumps, 15-minute cool down, metal tube still became too hot to touch. Out of service with blown "O" ring, I studied a 2-part YouTube video by Coby Leo of Topa Manufacturing Company, regarding repairs and rebuild. Part way into the dis-assembly demonstration, Coby tilts the tube and pours out the liquid coolant into a cup. Upon reaching that point in my dis-assembly, tilted tube, nothing came out. NO COOLANT INSTALLED. Completed repairs, refilled with mineral oil for coolant, and tested. Pump works fine and never gets any more than warm to touch. Back and forth with seller until they refunded $10 to my credit card. (Seller wanted a picture proof of missing coolant so I sent one of an empty cup.) I'd recommend checking out Coby Leo's videos, just to be prepared. WM 
 
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The pump very well may work when it does that but it is NOT normal. Neither of mine do now that I partially rebuilt them. Neither of mine had any coolant in them either. They are super easy to work on and the rebuilt kits are cheap and available on eBay. There are basically only two places that fail on them. The check valve at the bottom like stated and the very end of the rod that compresses the air in the final pump chamber. On the end of that rod is an o ring and another Teflon or polymer piece. These go bad periodically and need replacement. I have been maintaining mine better and they seem to be holding up really well. Every week - two weeks I take the pump off the foot base. Then remove the check valve and clean and relube that o ring. I then spray some ballistol up into the final pump chamber that is right behind where the check valve sits. I then pump it a bunch of times so the ballistol cleans and lubes the chamber. I then add a drop of silicone oil into the same chamber and pump it a few more times and then put it back together. 
 
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I couldn't help tinkering with it before my 22 cal Air Venturi Avenger arrives later today. I broke it down and fiddled with the check valve hold down screw. It seemed overly tight so I loosened it a bit. The pump had no coolant in it, contrary to the owner's manual which stated that water has already been added. I liked 'WorriedMan's' mineral oil idea, so that's what I put in. I was very impressed with how quickly the mineral oil cooled the assembly to my touch.

Once reassembled it's behaving much much better.

John Ponzo - aka Ponz


 
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Ponz,

Good deal, mineral oil was shared from another member a while back, so I can only take credit for passing on the information. I know Coby Leo's accent can be hard to follow, however, not hard to follow his work. I've moved on to a Yong Heng after adding a few higher fill capacity PCPs that took the joy out of shooting considering the handpump workout ahead. Also, found I'd pumped some moisture in my Gauntlet with the handpump. This is my current air fill station, coalescing filter followed by three additional, only cleanest, driest air for my guns now. Best of Luck,
IMG_20220322_203924.1649342515.jpg
WM
 
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Grumbly said:
I also have one of the cheapie chinese hand pumps. The check valve at the bottom of the pump tube is the weak point and mine often leaks. Unscrew the pump body from the base, and at the very bottom of the pump body will be a small threaded cap. Behind that cap is a spring, check valve w/ oring. Look closely at that o-ring and see if it has any spots that look like they've been ablated. If you see any damage, replace that o-ring with one that came in the spare parts kit that shipped with your pump (hopefully). I go through these o-rings fairly quickly, each one lasts about 5 fills on my pump. I ordered bulk replacements from amazon for cheap.



https://www.amazon.com/dp/B015O321K4?psc=1&ref=ppx_yo2ov_dt_b_product_details



These are slightly bigger than the original but work just fine in both the check valve and on the high-pressure piston inside the pump.

If you put water in the pump, it will help your orings live longer since they don't get quite as hot. I learned that the hard way.
Click to expand...
Just an update to this thread. I have the same problem these orings go bad. I’m thinking it is a metric size. I ordered 006 not 007 and they work in the same manner. They work but not for long which tells me they aren’t quite right. Apparently 007 isn’t either. I just picked up a metric kit from harbor freight and will report back if I find one in that which works better.
 
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When it comes to o ring kits, wether amazon kits or harbor freight, I’ve gotten lucky in finding one exactly what is required one time, and that was for the o ring under the valve on an scba tank.

On times whenever I try one “that’s close”, probably twice out of 10 tries, and one of those two attempts the wrong o ring failed.

It’s best to grab the sizes as best you can from the old factory ones and order replacements from either the selling VENDOR or from an o ring supply house. I would think viton would be the best for hand pumps as they can take a lot of heat.

Just my own personal experiences. I’ve owned two kits from Napa both in metric and inch and they are still 90% full, for being 15 years old, so that should tell you something about relying on kits
 
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Bigragu said:
When it comes to o ring kits, wether amazon kits or harbor freight, I’ve gotten lucky in finding one exactly what is required one time, and that was for the o ring under the valve on an scba tank.

On times whenever I try one “that’s close”, probably twice out of 10 tries, and one of those two attempts the wrong o ring failed.

It’s best to grab the sizes as best you can from the old factory ones and order replacements from either the selling VENDOR or from an o ring supply house. I would think viton would be the best for hand pumps as they can take a lot of heat.

Just my own personal experiences. I’ve owned two kits from Napa both in metric and inch and they are still 90% full, for being 15 years old, so that should tell you something about relying on kits
Click to expand...
Yeah probably true. Another update. When that oring starts going bad and leaking back into the pump change it right away or at least don’t force the handle back down. Just happened to me today. The oring allowed air to leak into the compression chamber. Instead of me just bleeding it and then changing it I forced the pump back down with all my weight. This blew out the tiny oring (same size as the check valve one) on the end of the compression rod. Luckily I had 2 OEM orings left so I tore the pump apart and fixed it. Maybe I will try to measure the other little tiny one and see if I can find them. Other choice is the pump rebuild kits are like 6 or 7 bucks on eBay but you only get two of those small orings in each one and that kind of sucks when those are all you need.
 
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