How To Repair A Bengamin Air Pump

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Topic: Benjamin Mitt Pump Maintenance, Modifications and Reliability  (Read 16094 times))

I thought I would start a thread regarding the Benjamin paw pump and chronicle my experiences with it and effort and provide any technical insight into the care and feeding of this common PCP pump. Also, I wanted to certificate any upgrades or changes I made to the pump over time, how long it has lasted between maintenance needed and its overall operation.

Start, the pump I accept was bought used so I had no thought of its history every bit in how it was treated or if any maintenance was done, but upon its arrival information technology was clear the pump had seen use. Non in a bad way, but used.

I used the pump to do my initial sight in with the .25 Marauder and it felt similar the pump was working a little harder than it needed to pump the gun up to 3000psi. I decided since I didn�t know the pumps history a couple rebuild kits from Sunday Optics ($xiii.00 bucks shipped to my door) were in order. I didn�t want to keep using the pump until I had gone through it to verify its internal status.
While waiting for the rebuild kits to arrive I read all the threads on the GTA and Marauder forum on the who�s, what�south and why�s of the Benjamin pump including upgrades (i.due east. boosting) and general intendance and feeding. I too watched every YouTube video I could find on how to pull the pump down. This is keen information and I didn�t mail pictures of the tear downwardly because they exist in and so many places I idea information technology redundant. As well, that isn�t quite what this thread is about.

A week later the rebuild kit arrived so I broke out the hand tools and began disassembly. I thing, Sun Eyes proves a few actress O-rings, but not doubles of EVERYTHING. I have to say, the pump is very, very simple and comes apart with a minimal of hand tools. A few adjustable wrenches and I had it apart rather apace. The but issue was unscrewing the valve from the final piston bottom was really hard equally it was this pumps first fourth dimension being disassembled. The videos are correct, that was hard. But when y'all re-tighten the bottom valve to the internal piston you don�t torque the heck out it and so you won�t accept to confront that again.

Ane thing was immediately clear; that petty contumely filter doesn�t filter &^^&! Well maybe it keeps out insects, rocks and modest children walking buy while pumping merely the pump was full of moisture and whatever grease used to lube the pump was black and nasty. As I tried to remove the black goo and wet I started to get through rages chop-chop and the lube didn�t want to come up all the way off. So I grabbed my rubber gloves and took the parts to my garage and used a can of spray restriction cleaner. That removed the nastiness perfectly! I went over each role afterward cleaning and inspected them closely. The machining in some spots is a piddling crude. I had removed the original O-rings BEFORE the brake cleaner was used and inspected them while I let the brake cleaner flash off the parts. Upon wiping off the blackness goo I was surprised to encounter the O-rings were still in very practiced shape! Even the mutual #007 O-band that fails was PERFECT! I was tempted to re-use the O-rings just decided to start from new for my experiment.

One time all parts were cleaned and laid out with the proper O-rings. I began lightly applying the diver�due south silicone grease lightly to the O-rings and installing them. When I mean lite I hateful LITE!  That stuff is thick and gooey. You lot barely need any on your fingers to burnish the O-rings. I also applied on the main piston rod an even coating of 15 wt. 100 % percent silicone shock oil from the local hobby store. I also added a light coat of the silicone oil to some of the O-rings to assist in assembly. Earlier I knew it the pump was back together!

Now, the one modern I did do was add a desiccant filter. Lots of means to do this, again pictures are all over the GTA and Marauder forum. I think this modern is needed in some grade or fashion. You can go the filters from Harbor Freight, NAPA Motorcar, etc. I then went to ACE Hardware and spent 10 bucks in brass adapters and as yous tin can see from the picture show I know take a desiccant filter added to the Benjamin Pump. So for 20-thirty bucks in filters and parts you can have a decent filtration system.

This past Sunday I used the pump in its rebuilt condition and all I can say is there is a major difference in its performance. It adds a fiddling more air, runs cooler and smoother to kicking!
So correct now I am only going to utilize it and monitor its condition equally I shoot this summer. I will start taking pictures of ANY changes I make or maintenance performed. Forgot to add, the first time I used the pump the gauge on the pump did not quite match the gauge on the K-Rod. Afterwards the rebuild now they do

I remember it�south rubber to say it is NOT the best pump in the world, merely it reminded me of the Marauder burglarize itself. Rough effectually the edges in spots, but works overall if taken intendance of. Too, with some possible �custom� work made even more reliable and meliorate. I may polish some internals simply equally not everyone has admission to machining parts, let�s see how it does with regular upkeep.

So my first suggestion if you own one of these pumps is to put a filtration system on it�that appears to be a weak link.

To be continued�

BZ

« Last Edit: April 30, 2022, 08:22:01 PM by Bubba Zanetti »

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• Delaware

"End Starlings...with extreme prejudice".

Air Arms S500 HFT
BAM-50 .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .20 cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 Ten 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

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Thanks, Dan.  I'k not sure what pump I'thou going to terminate up with, most probable the Benjamin since that's 90% of what they sell downwards hither.  Air Venturi is the other option.  Anyway, thanks for your feedback on the rebuild.  A lot of folks complain about them, but I'one thousand curious as to how many take taken the time to ensure they are properly assembled, cleaned and lubed.  The right attitude has a lot to practise with our experiences likewise.

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• Risaralda, Pereira, Republic of colombia

I'grand a peaceful man and prefer the pursuit of peaceful sports.  Those involving teams and balls of whatever sort tend to be deleterious to one'due south body and promote violence by both spectators and participants.   The shooting sports, yet, tend to promote cocky control and are peaceably participated in past those who know that their greatest challenge is their need to continually hone their ain abilities.

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Why wait?? Boost that pump and cut the pumping in half. Satisfy your lazy half and enjoy shooting twice as much.

Logged

• Kingwood TEXAS

Take a walk on the "DARKSIDE"
Flying Dragon FDPCP .177 cal.
Daystate Huntsman Regal XL .22 cal./Hawke Airmax 30 3-12x
Mrod Gen1 .22 cal. w/MDRL Bullpup/UTG
Mrod Gen1 .25 cal. westward/MDRL Bullpup/UTG
Crosman Titan .22 cal. (Gave to son)
Crosman 2240 .22 pistol
Crosman 1377 .177 pistol (apx. 30 yrs sometime)
2 Gamo .177  Breakbbl Whatevers
2 Bug-A-Salts (Got Flys? Shoot um!)
TO Notice A LOCAL SHOOTING FRIEND
  CLICK Hither FOR THE GTA MEMBERS MAP  >>>  https://world wide web.zeemaps.com/map?grouping=962067
and so add together yourself

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I have had mine for two years.
I follow Tom Gaylord's instructions to the alphabetic character.
Use those knees.
Keep the shaft  lubed with silicone.
Yep I put the desiccant filter on (in the right management) (The desiccant tin be emptied, dried and re-used) too.
I have a compressor and a Guppy but I use the pump for the PRod and the 1701P.
Now that you lot have the .25 pressurized it will simply take nearly 75 pumps to go it from 2000-3000psi.
Of grade if you de-gas the gun to empty information technology volition accept more...
Stay safe and free.

Logged

• Fairfield, CA, United states of america

AA TX200, .177
Avanti 499B
Baikal IZH46M
Baikal IZH60
Beeman P17
Beeman R1, .177
Benjamin Marauder, Gen I, .177
Benjamin Marauder, Gen I, .25
Benjamin Marauder Pistol
Crosman 2300S
Daisy Model 25, Variant 7
Diana 6M
Sheridan C9a
Weihrauch HW35e, .177

---

Logged

• Kingwood TEXAS

Take a walk on the "DARKSIDE"
Flight Dragon FDPCP .177 cal.
Daystate Huntsman Regal 40 .22 cal./Hawke Airmax 30 3-12x
Mrod Gen1 .22 cal. w/MDRL Bullpup/UTG
Mrod Gen1 .25 cal. w/MDRL Bullpup/UTG
Crosman Titan .22 cal. (Gave to son)
Crosman 2240 .22 pistol
Crosman 1377 .177 pistol (apx. 30 yrs old)
2 Gamo .177  Breakbbl Whatevers
ii Bug-A-Salts (Got Flys? Shoot um!)
TO FIND A LOCAL SHOOTING FRIEND
  CLICK HERE FOR THE GTA MEMBERS MAP  >>>  https://www.zeemaps.com/map?grouping=962067
so add yourself

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1st update.

Shot 140 pellets Dominicus during a very extended pest hunt on a dairy farm. This is the well-nigh I accept shot the M-Rod in one sitting. It took roughly sixty-65 pumps to get from 2000 psi to 3000 psi for 24 accurate shots.

If I did the math right that is 325 total strokes on the pump throughout the day.

Pump didn't miss a beat.

BZ

Logged

• Delaware

"Terminate Starlings...with extreme prejudice".

Air Arms S500 HFT
BAM-50 .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .20 cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 10 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

---

2nd update and 1st failure.

In defence of the pump, my last couple of shooting sessions I kind of torture tested the Benji pump. Lesson? Let it cool down. In Hot conditions that means really allow it sit down for ten or more minutes to absurd IN THE SHADE! Also, when your desiccant filter beads turn pink, alter the filter. I didn't and got a little moisture in the pump.

Pulling the pump downwards the merely O-ring that failed was this one in the valve. seen here in the pics.

All other o-rings were yet well lubed and in excellent condition. A new o-band and x minutes later on I was back up and running.

Why did information technology fail? Heat and it somehow grabbed and rolled the o-ring tearing it. I could not experience any issue it just would not fill by 700psi.

So let this pumps absurd and take your fourth dimension pumping. Pump lasted near 300-400 shots. That last l is when I beat on the pump and it didn't take much to roast that o-ring.

Now I am going to try for longevity and see what happens.

Till Next fourth dimension

BZ

Logged

• Delaware

"Terminate Starlings...with extreme prejudice".

Air Arms S500 HFT
BAM-fifty .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .20 cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 X 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

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I will be watching this.
Lord's day optics sell a desiccant filter for $25 shipped for the pump,and is somewhat larger than the one you assembled.

Logged

• Houston, Tx.

I brand 2 predictions;
ON THE Appointment WHEN US TROOPS ARE ISSUED AN Free energy Pulse Weapon,
1. The Us Soldier will have on his person a version of the Colt 1911.
ii. He will be aiming the NEW Weapon at someone carrying an AK47.

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Hey Bravo:

That was just information technology. The price of the Sunoptics kept me form ownership information technology. The one on the pump came in a two pack for 20.00 at the NAPA car store and Harbor Freight has them for 8.00 each which I might effort 1 of those when the ane on the pump is no longer expert. Pretty sure the HF ones are a little bigger too.

If I modify it I'll document information technology

BZ

Logged

• Delaware

"Terminate Starlings...with farthermost prejudice".

Air Arms S500 HFT
BAM-fifty .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .20 cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 X 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

---

Boost and do it in +-xxx.

Kyle:

Not ignoring you merely not interested in "boosting" the pump for a host of reasons. The main ane existence not everyone has the fourth dimension, tools and talent to boost a pump. But they do have the fourth dimension, tools and talent to maintain and repair a pump.

Its a not bad modification for those whom information technology will suit.

BZ

Logged

• Delaware

"Terminate Starlings...with extreme prejudice".

Air Artillery S500 HFT
BAM-50 .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .twenty cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 X 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

---

2nd update and 1st failure.

In defense of the pump, my last couple of shooting sessions I kind of torture tested the Benji pump. Lesson? Let it cool downward. In Hot weather condition that ways really allow information technology sit for 10 or more minutes to absurd IN THE SHADE! Also, when your desiccant filter beads turn pinkish, change the filter. I didn't and got a little moisture in the pump.

Pulling the pump downwards the but O-ring that failed was this 1 in the valve. seen here in the pics.

All other o-rings were however well lubed and in excellent status. A new o-ring and 10 minutes later I was back up and running.

Why did it fail? Heat and it somehow grabbed and rolled the o-ring trigger-happy information technology. I could not feel any issue it just would not make full past 700psi.

So let this pumps cool and accept your time pumping. Pump lasted about 300-400 shots. That final 50 is when I beat on the pump and it didn't take much to roast that o-ring.

At present I am going to try for longevity and see what happens.

Till Next time

BZ

Are you maxim the o-ring that seals the inner tube to the check valve body where it screws in failed? Not sure how that could "roll" during uses every bit that inner tube does non move, correct?

Logged

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I was just given a Benjamin pump, that I don't know the history of, and it does have issues as it is, and it doesn't have a fill hose.

(Hey the price is correct, FREE)

It is going to lord's day optics Tuesday with a check, ($25 for a complete rebuild and refurb, $v for a new fill hose with foster connexion, and $25 for the filter)

So for $55 total, I become to commencement from a known point with a working pump.
And a filtration/dryer system.

Logged

• Houston, Tx.

I brand 2 predictions;
ON THE DATE WHEN US TROOPS ARE ISSUED AN Free energy Pulse Weapon,
i. The The states Soldier volition accept on his person a version of the Colt 1911.
ii. He volition be aiming the NEW Weapon at someone conveying an AK47.

---

Big Tin Boat:

I wish I could take better pictures because the tear in the o-ring was weird. In the short the oestrus from failure to allow the pump absurd deformed the o-ring and when I pulled the tube out of the housing that's when it probably caused more damage. Mayhap I didn't use the correct language in describing the failure initially.

Its not the o-band I thought that had failed that's for certain.

BZ

« Last Edit: July fourteen, 2022, 09:25:24 AM by Bubba Zanetti »

Logged

• Delaware

"Terminate Starlings...with extreme prejudice".

Air Artillery S500 HFT
BAM-50 .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .twenty cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 X 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

---

Nice bargain Bravo! 55 bucks would work for me

BZ

Logged

• Delaware

"End Starlings...with extreme prejudice".

Air Arms S500 HFT
BAM-50 .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .20 cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 X 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

---

Big Tin Boat:

I wish I could take improve pictures because the tear in the o-band was weird. In the short the heat from failure to allow the pump cool plain-featured the o-ring and when I pulled the tube out of the housing that's when it probably caused more damage. Maybe I didn't apply the correct language in describing the failure initially.

Its non the o-band I thought that had failed that'south for sure.

BZ

Gotcha - information technology's usually the 007 on the end of the inner rod. Since that inner tube is threaded my approximate would be that you lot probably "nicked" that ring on installation, which was and so furthered past the estrus.

What I found is that my pump moves easier and I seem to get lees heat since I went to 100% silicone "oil" for assembly instead of "grease". I used the stuff RC cars use in the differential.

and  45 - yeah $55 is a a deal, especially the $v for hose with fitting. Heck the cheapest I found foster fittings was about $12 for a pair.

Logged

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Big Tin Gunkhole:

I wish I could take amend pictures considering the tear in the o-band was weird. In the short the heat from failure to let the pump absurd deformed the o-ring and when I pulled the tube out of the housing that's when it probably acquired more damage. Peradventure I didn't apply the correct language in describing the failure initially.

Its not the o-ring I thought that had failed that's for sure.

BZ

Gotcha - it's usually the 007 on the stop of the inner rod. Since that inner tube is threaded my guess would be that you probably "nicked" that ring on installation, which was then furthered by the heat.

What I found is that my pump moves easier and I seem to get lees heat since I went to 100% silicone "oil" for associates instead of "grease". I used the stuff RC cars utilize in the differential.

and  45 - aye $55 is a a deal, particularly the $5 for hose with plumbing equipment. Heck the cheapest I found foster fittings was well-nigh $12 for a pair.

Yup, I have a Hobby Store in Seaford, Delaware were I got my 100% silicone daze oil for $4.50. You are correct, great stuff and information technology lubes very, very well. Don't need much

I idea the 007 ring would exist toast besides, merely looked great. The one Dominicus Optics at present sells in the rebuild kit is a white one (the name of the fabric escapes me, Mac 1 uses these types of O-rings) and it was fine.

I will proceed an eye out if I nicked that o-band. I am usually pretty practiced well-nigh such things, but I love suggestions as its more to explore.

BZ

Logged

• Delaware

"Terminate Starlings...with extreme prejudice".

Air Arms S500 HFT
BAM-50 .177 (Lemmy, from Motorhead)
1970 Racine Sheridan .xx cal Mac1 Steroid
Drozd Bumblebee on HPA
Crosman 150 X 2
Crosman 113
Crosman 111
Umarex M712
Beeman P3

---

Yup, I have a Hobby Store in Seaford, Delaware were I got my 100% silicone shock oil for $4.50. Yous are correct, groovy stuff and information technology lubes very, very well. Don't need much

I thought the 007 ring would be toast too, but looked bang-up. The one Sunday Optics now sells in the rebuild kit is a white i (the name of the cloth escapes me, Mac 1 uses these types of O-rings) and it was fine.

I will keep an eye out if I nicked that o-band. I am usually pretty proficient about such things, merely I honey suggestions every bit its more to explore.

BZ

I was going to get the shock oil but it seemed too thin, that's why I went with the differential oil (I call back the 5500w). Same oil just diff "thickness".
Also - I did non use the 2 o-rings on the rod, I made a "washer" from a nylon bushing to supervene upon the white o-ring. Seems to be working meliorate for me and so using the white and black o-rings together from the "kit". That and a xc duro viton ring seems to no long "whorl".

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BTW...
You do not have to change the filter (The ones from Harbor Freight).
Open them (Unscrew the caps), dump the dessicant onto an aluminum tray and heat in the oven aat 300 degrees til they turn blue.
An old toaster oven (garage sale item) works very well for this...

Logged

• Fairfield, CA, Us

AA TX200, .177
Avanti 499B
Baikal IZH46M
Baikal IZH60
Beeman P17
Beeman R1, .177
Benjamin Marauder, Gen I, .177
Benjamin Marauder, Gen I, .25
Benjamin Marauder Pistol
Crosman 2300S
Daisy Model 25, Variant 7
Diana 6M
Sheridan C9a
Weihrauch HW35e, .177

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I thought since this a Benjamin production,
I chosen Crosman (since they own Benjamin) to run across what their cost was on servicing a pump either in or out of warranty.

Their response was that they don't do any servicing of the pump.
It would take to go,to the manufacturer, and they gave me sun eyes number.

I called Duane Sorenson in that location and we talked about the pump, and what should I do to maintain it.
And I asked about lube.

He says when they assemble them, they use Mobil I pure synthetic oil.
And suggested that I utilise a drib or two of that on the outside tube for lube if any is needed.

I asked well-nigh silicone as a lube, he says that the Mobil 1 has a higher flash point than the pump, or PCP guns tin produce.

I did find it interesting, that the manufacturer would suggest using something other than silicone that everyone else (end users) propose..

Just hey, they brand it, and know a whole lot more nearly their product than I do..

Any thoughts on that?

« Last Edit: July 15, 2022, 03:fifteen:57 PM past 45Bravo »

Logged

• Houston, Tx.

I make 2 predictions;
ON THE Date WHEN United states TROOPS ARE ISSUED AN Energy Pulse Weapon,
1. The US Soldier volition have on his person a version of the Colt 1911.
2. He will be aiming the NEW Weapon at someone carrying an AK47.

---

I asked nearly silicone as a lube, he says that the Mobil One has a higher flash point than the pump, or PCP guns tin produce.

I did discover information technology interesting, that the manufacturer would suggest using something other than silicone that everyone else (finish users) advise..

But hey, they make it, and know a whole lot more nearly their product than I exercise..

Any thoughts on that?

The spec sheet I found for the Lucas Silicone oil I use says that it has a flash signal of 572 deg F. Depending on the weight of the Mobil One I've plant figures that vary in the 400-500 deg F range. I have no clue equally to what temps the PCP or Pump can generate

Logged

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