TargetTalk

Try to pump cylinder with Hill pump today.

Handle of the Hill pump kept popping back, can't push air in.

Disconnect cylinder, Hill pump seems to pump air out all right.

Connect cylinder, Hill pump handle could not be push down again.

Hill pump problem or cylinder problem? I unscrew the cylinder cap, all seals looked all right. Connect the cylinder cap only to the pump, with no cylinder container, I can pump air out through the cylinder cap.

Why once the cylinder container is reconnected to cylinder cap, I can't pump the Hill pump any more?

Is this a recent problem/issue ?
Is this the first time using a hand pump ?
Got to start with the basics here cause this is the internet and I cannot see what your seeing :)

This is Daryl Szerenski's Hill pump. He gave it up after London.

It worked flawlessly until now.

I don't think it is the cylinder problem. I opened cylinder up, rechecked all the seals and coil spring. All seem in order.

I suspect it is the pump. When encountered resistance, pump does not seem to hold its one way pump action. Handle pops back up. Press it down, it pops back up without pressurizing the cylinder.

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seamaster wrote:Handle of the Hill pump kept popping back, can't push air in. Hill pump problem or cylinder problem?

Is the pump the MK3 or MK4 version? When the handle of any pump keeps popping back up by itself, an o-ring is worn or the pump has some gunk in it and needs to be disassembled, cleaned and relubed.

It's probably the check valve or air exchange valve seal. Contact Hill and tell them the problem, they might even send you the o-ring(s) for free. There are many videos on the internet that shows you how to service your Hills pump.

http://www.airriflepump.com/

I had a similar problem (don't recall if it was exactly this or not..) after not using the pump for a long time. Something froze up inside. I compressed the handle all the way down until it hit bottom, and that jarred something loose & it's been fine ever since.

I think it's definitely the pump. They sell rebuild kits, and I suspect it's for a reason...

Mine is doing the same thing right now. It is a Mk4 that was new in June of 2015. We emailed an enquiry to Hill to find out if this requires a complete rebuild or if it is something specific and got a quick reply saying that it is most likely just one seal, however since the pump must be disassembled to repair the problem a complete rebuild is the way to go. They are sending me a kit, gratis.

That is good customer service in my book.

m1963, good for you! That clearly shows they stand behind their product and are willing to provide an excellent aftermarket service to make customers happy and loyal.

I bet you don’t have to replace all the seals; I think it’s the innermost small o-ring that gets worn. That particular seal handles most of the pressure and heat generated in the pump. Don’t pump longer than five minutes, allow the pump to cool down to extend the service life of the o-rings.

I've become quite the pump expert after having owned a Benjamin pump (two actually!) for 3 years now. One pump works well most of the time, and is easy on the O rings. The other is my frequent failure pump that I'm gradually improving at each rebuild. The Hill type pumps are actually three pumps in one. The O rings separate each pumping stage to allow air to enter (the pulling stroke) the low pressure chamber (the large tube), move thru the second stage (the middle tube), and exit the high pressure chamber on the down stroke. Because each stage is tightly sealed by the O rings, you need to allow about 2 seconds for the up stroke, pause, and push firmly down until the pump bottoms out. This final push , "pops" the high pressure check valve off it's seat, overcomes the higher pressure of your pistol's cylinder, and pushes that small, high pressure puff of air into your gun. It pretty incredible that the pump can take atmospheric air pressure to over 4.000 psi! OK, enough pump theory for now.

One of the common cause of failure in these pumps is the small O ring(s) on the end of the high pressure shaft. When those rings wear, air won't be pushed out into the line and into your gun. The next and most common cause is the failure of the second stage O ring. This O ring is located in the top of the main housing that the middle tube screws into. It is an internal ring that must be removed with a small jewelers screwdriver or a metal hook. If this ring fails your pump will behave as you indicate. The wear may not be apparent either! Make sure you replace this ring with Viton, not Buna N (a soft rubber compound not conducive to wear). My pump takes a 10 mm O ring commonly used in scuba take yokes. Use silicon grease to lube it well, and if the threads on the second stage tube are sharp, take some steel wool or fine sandpaper to "take the knife edge off the treads so they don't feel like they can cut your finger. Press the Viton O ring back into the internal slot (be patient and work with a smooth rod (even a section of coat hanger will do if the ends are square and NOT sharp) to help force it into the groove.Lube the threads on the second stage to avoid cutting the O ring on reassembly.

While you have the pump apart, make sure the high pressure spring check valve O ring is good, blow out the small ports in the pump with compressed air or a computer keyboard duster, Take out the second stage ball check valve located at the top of the pump under the handle. Clean it and put it back with no lubes. Check any other O ring seals and reassemble the pump using a thin coating of silicon lube or synthetic motor oil. Note: regular motor oil is flammable at lower temps and there is a remote possibility of ignition. There is NO NEED to reassemble the pump using brute force. Just a bit past hand tight is all that is needed. The O rings do the work, not your wrenches!

Its intimidating at first, but the YouTube videos and the exploded parts diagram will help. Once you do it a few times, you'll be the local expert. Make sure you have a few hours for the first rebuild, and your favorite beverage available, Also make sure the mom, girlfriend, or wife is occupied, as you will be deep in thought and won't be inclined to tolerate interruptions LOL.