Benjamin Hand Pump - Sun Optics Repair Instructions

Benjamin Marauder Troubleshooting
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Benjamin Hand Pump - Sun Optics Repair Instructions

Postby zae333 » Mon Aug 02, 2010 7:40 am

My repair kit arrived from Sun Optics today (ironically, one day after I purchased the necessary o-ring from Lowes and repaired the pump). I have decided to post these instructions here for anyone who runs into the same problem I had with my pump. Most of these "vacuum" problems are related to the highlighted o-ring P-30 which can be seen in figure 9 on the last page. Oh, and I did NOT highlight that o-ring, the guys at Sun Optics knew which one was the problem from my conversation with them over the phone and already had the problem o-ring marked for me. I have also included a picture of the o-rings just in case someone's curious. (I know we've all seen o-rings but whatever, right...lol...) Hope this helps someone down the road.

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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby dogwood » Mon Aug 02, 2010 9:23 am

nice, thanks for sharing - no problems with my pump so far, hoping it stays that way :D
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby hawkeye » Mon Aug 02, 2010 2:51 pm

Great Post. This is the first time I've seen the instructions in English!! :) My Spanish is no so good.

Thanks Again
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby stewy63 » Mon Aug 02, 2010 7:42 pm

Excellent!
Thanks.

Brian
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby Rob » Wed Sep 08, 2010 6:49 pm

This is great thanks!!!
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby Bruce Jarrett » Fri Nov 12, 2010 6:12 pm

I've been using a Benjamin pump for about 2 weeks now and I'm starting to have the same problem with the handle hard to pull up. Has anybody done the cleaning and motor oil replacement and used the pump a lot since . I was wondering if the cleaning and gasket replacement is something that I will have to do on a regular basis. Gasket replacement every two weeks could be a pain. I could return my pump since I have a 30 day return policy and buy a hill pump.
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby Walx » Sat Nov 13, 2010 11:21 am

I think the pump is very dirty when it is shipped. After mine stopped working and I took it apart I could see why it didn't last long. There was a lot of grit. I would think that it should last a lot longer after it is cleaned and the orings replaced. If you do return it I would go with a tank and not another pump, You wouldnt regret it.
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby zae333 » Sat Nov 13, 2010 2:23 pm

Unfortunately, I end up replacing the third-stage o-ring at least once every 6 weeks. If you are going to keep the pump, then set aside an hour or so every few weeks to repair it.
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby Bruce Jarrett » Sat Nov 13, 2010 8:07 pm

Zae333
You said in another post the #60 o rings at Lowe's was too small. I noticed Lowe's has a ticker #78 o ring did you try them ? Since you are repairing every 6 weeks or so where are you getting the o rings ? Is Sun Optics sending these to you or are you buying them . O rings don't cost much it's just knowing the correct size. Are you replacing all the o rings every time or just P30 ? Did the 10w 40 motor oil seem to work better then the silicon grease that was in it originally ? Do you think full synthetic motor oil would be better ? I would like to stay with the Benjamin pump if practical. Sorry for all the questions but with my gun shooting great I'm trying to learn about the weak link , the pump. Thanks
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Re: Benjamin Hand Pump - Sun Optics Repair Instructions

Postby zae333 » Sun Nov 14, 2010 3:43 am

I noticed Lowe's has a ticker #78 o ring did you try them ?
- Yes, they are too big. I also tried a #36, which is very, very close to the right size but still, too big.

Since you are repairing every 6 weeks or so where are you getting the o rings ?
- The repair kit Sun Optics sent me came with 6 o-rings. I am down to only two left. I have not found a source for good replacements yet.

Are you replacing all the o rings every time or just P30 ?
- No, the other o-rings are holding up just fine. It is only P30. I've replaced it so much that I can do it in about 15 minutes now.

Did the 10w 40 motor oil seem to work better then the silicon grease that was in it originally ?
- I have not tried using this on the whole pump, just the P30 O-ring and unfortunately, it doesn't make much of a difference.

Do you think full synthetic motor oil would be better ?
- It actually might, at my next replacement I'm going to try that.

I'm actually in the same boat with you Bruce. My gun shoots amazingly, 1/2 inch groups at 45 yards and sub 1/4 at 20 yards. The pump is definitely the weak link but it can be repaired very quickly once you master disassembling it. And my 6 week repair schedule is a rough average, I shoot a lot, sometimes filling my Marauder from 2100 psi back to 3000 psi 3 - 6 times a day on weekends and at least 3 more times throughout the week. So my pump may get quite a bit more use than say your average shooter's. I'm looking into buying higher quality Viton orings or better, I'll post back with the exact sizes for the P30 oring. Got to get new batteries in my calipers.
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