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Benjamin Hand Pump - dismal quality causes failure

December 13 2010 at 5:31 PM
leonardj  (Login leonardj)

This Benjamin hand pump came to me a short while ago having failed after the owner had only used it about 5 or 6 times to pump up his Disco. I have been waiting several weeks for the rebuild kit to arrive from the supplier of the pump - Sun Optics, in Texas. I first tried to obtain the kit through the Canadian Crosman Distributor, but after several weeks of trying without success, he just gave up, and gave me the contact info for Sun Optics. I called them, and explained the situation to them, and that neither I, nor the owner of the pump were pleased with the lack of interest shown by them in providing the rebuild kit. I was assured that they would send a kit to me ASAP, free of charge, and after almost a week and a half, I had pretty much given up hope on receiving it. But today, I was pleasantly surprized by a package in the mail - the long awaited rebuild kit had arrived.

Having given up on ever getting the kit from Sun Optics, I had already taken the step of trying to identify the correct o-ring sizes for the pump, so that I could order them through my regular source. As I cleaned up the old o-rings, it was clear why the pump had failed. There are 13 o-rings in the pump, and every single one was badly abraided and nicked. They were all so bad, that it was difficult to get any proper dimensions, because in some cases, the o-rings had an eliptical cross section, rather than round. Further investigation revealed the cause - the sliding surfaces of the pump were abysmal - scratches and gouges everywhere - it appears to me that these surfaces were never polished smooth, thus, the o-rings were ground away in no time. Some o-rings had deep nicks in them that could only have occurred during assembly. The pics will illustrate the deplorable quality encountered.

The o-rings - note the deep abrasions, and tattered edges, as well as deep nicks on them. The lower left pic is the final stage check valve seal - almost half the top section is missing. The bottom right pic is the 5.5 mm rubber ball check from the second stage piston. This is not included in the
rebuild kit, because as the representative put it, "that ball will never wear out". Apparently someone forgot to make this badly abraided ball aware of that.

[linked image]

The ball check seat is completely covered in sharp, jagged burrs, and almost appears like it was machined with a hammer and chisel. Two very light, plastic washers act as retainers and I presume, a tensioner for the ball check. Both of these are in pretty rough condition, and should be replaced IMO, but alas, these are also excluded from the rebuild kit as "un-necessary". The circlip on the left is the one from the pump, and is exactly as found - it is believed that this pump was a "factory refurb", yet sold as new. (more evidence of this to follow) It appears that the circlip was pryed off, rather than the use of the appropriate snap-ring pliers. This is exactly how it came off - I only gave it a flick with my fingernail to remove it. The brand new circlip on the right shows how badly mis-shapen the OEM unit is.

[linked image]

The final stage piston is clearly canted on the end of it's rod - this can be evidenced by the heavy wear on the top rear edge of the piston in the

upper pic, and the lower front of the piston in the lower pic. The front of the piston is no longer round, but eliptical. The back up washer for the piston seal is also not included in the kit, again, presumably because it was not considered "needed".

[linked image]

The OD of the intermediate piston has numerous tooling marks leading me to think that it was held in a bench vise at some point in time. (Again - supplier refurb?).

[linked image]

This is the second stage rod - it is not hard to see why the o-rings have been shredded. From top to bottom, the top section of the rod, the middle section, and the lower section.

[linked image]

The first stage rod - lower, and mid section.

[linked image]

And finally, the outer tube, showing the obvious use of slip joint pliers on it. The owner tells me that this is how the pump came out of the box when he bought his Disco package, but really hadn't paid it much attention until I pointed it out when he dropped the pump off in person. This is another reason that I firmly believe that this particular pump is a supplier refurb, and IMO, should never have been sold as "new" with the gun.

[linked image]

 
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AuthorReply
leonardj
(Login leonardj)

Just keeps on getting better.......the saga continues.....

December 16 2010, 1:59 PM 

So, I opened up the o-ring kit supplied by Sun Optics, Supplier of the Benji hand pumps, and much to my disappointment, I found that only 11 of the 13 o-rings were supplied. After further inspection, I discovered that of the 11 o-rings supplied, only 5 of these o-rings corresponded to sizes used in the pump.

As well, all attempts to source the 5.5 mm rubber ball, both online, and calling around to a few local businesses proved futile.

I again contacted Sun Optics, and once again, spoke with Duane. He assured me that all the supplied o-rings would, indeed fit the pump. I disagree, and the pics below will clarify my position. When I further explained that there were simply not enough o-rings in the kit to replace all the o-rings in the pump, I was told that not all of them had to be replaced. I explained that virtually every o-ring in this pump was shredded, including the 5.5 mm ball, Duane told me that he would put together another kit, including the 5.5 mm ball (which I had been told earlier was not available), and drop it in the mail to me. The wait begins anew.

In the pics below, the upper pic shows the 11 o-rings supplied in the Sun Optics kit. I was told that the reason for the extra pair of the smallest o-rings, is because these are the ones that fail most often, and that most the other o-rings can just be re-used. The lower pic shows the 13 o-rings that were removed from the pump. You can clearly see that a few sizes are missing. Please note that the pics are not to scale.

[linked image]

The following pics compare just a few of the o-rings as removed from the pump (left side o-rings in all the pics), against the nearest potential size o-rings as supplied in the kit. In some cases, the ID is out by a full mm, and in some the cross section is out by as much as 1.5 mm, and in some cases, both the ID and the C/S is different. Yet they are all supposed to "fit".

[linked image]

I will continue this update when the next rebuild kit arrives.



 
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leonardj
(Login leonardj)

A failing grade for Sun Optics.......

February 7 2011, 7:02 PM 

I have been a bit remiss in updating this thread in hopes that I could eventually post a positive outcome, but alas, it doesn't appear that it is going to happen.

I received a second "rebuild kit" from Sun Optics on January 7, 2011 - and to my extreme disappointment, Duane DID NOT include the rubber ball for the check valve as he promised that he would. In addition, the new kit, that was supposed to be a "more complete" kit, had essentially the same o-rings as the first kit, but with an extra four o-rings of no apparent relationship to the pump that I have apart - there are no o-rings even remotely close to the added sizes received in this second kit.

Once again, I called Sun Optics, and spoke with Duane, and expressed my disappointment that he had not included the rubber check ball, as promised in our last telephone conversation. Duane proceeded to repeat his spiel about how "those balls will never wear out", but when I pointed out to him that in our previous discussion that I told him specifically that the rubber ball in this pump was in fact damaged, and in need of replacement, he finally admitted that he did now remember, and apologised for not including the ball as promised. Duane asked for my address again, and promised that he would get a couple of these rubber balls out to me ASAP.

Well, here I am, four weeks later, and still no replacement ball check, and at this point, I have finally just given up on persuing this any further with Sun Optics. The owner of this pump has been patiently waiting for months now, and the supplier doesn't seem to care. The Canadian supplier with whom I first tried to source the rebuild kit from gave up in frustration when after several weeks of e-mails and telephone calls to Sun Optics, got him nowhere, at which point he gave me the contact info, and wished me luck. From my own experience dealing with these people, they lied to me - first telling me that the rubber balls for the check valve were not available, then in our next discussion, admitted that they did in fact have them. I was promised that a couple would be included in the second kit, but were not. Upon calling down there again, they tried to lie to me again, telling me that the balls were not available, until I persisted, and finally got Duane to "remember" his promise to send me a couple. And to conclude, the promise to send a couple of these balls out to me ASAP, was also, obviously untrue. So, after being ignored, and lied to for several months now by this company, I'd say that they deserve a failing grade.

I re-assembled the pump using what o-rings I could utilize from the two kits sent, and I still had to go to my local supplier to get a couple o-rings that were not in either kit. The pump is working, but I cannot be certain just how long it will continue to function properly with the chewed up rubber ball check. I don't plan to ever accept another one of these pumps for repair - it just isn't worth the frustration of dealing with the company that supplies these pumps to Crosman/Benjamin.

 
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