Problem With Benjamin Pump or Marauder

[Mark Mowrey]

Background info (Condensed Version):

• I get introduced to the Darkside with a Discovery and pump (Pump A) combo.
• I find a .22 Marauder with scope, pump (Pump B), and accessories deal walking around at a gun show for $400.
• I introduce a friend to the Darkside by selling him my Discovery and Pump B that I got in the Marauder deal.
• I buy a Synthetic .22 Marauder when it is released and sell my old Marauder to my friend.

Still with me?  I have a Synthetic Marauder using Pump A and my friend has an original Marauder and Pump B.

My Marauder was delivered on February 3, 2014.  After a few sessions, I begin to have problems with my Benjamin pump.  Ok, not that big of deal since I rebuilt Pump B before selling it and it is working fine.  I rebuild Pump A, and it still doesn't work.  I fight with it a bit and make a post on February 23rd to request assistance:
http://www.gatewaytoairguns.org/GTA/index.php?topic=62575.0

I get tired of messing with Pump A so I reduced my shooting and use my friend's Pump B to fill up the few times we get together to shoot.  Part way through the session, his Pump B fails on my SynRod.  I rebuild it and it is fine.  This happens on maybe 3-4 more shooting sessions throughout the year.  His pump B works fine for him until we get together and it fails on my SynRod, every time.

The Real Question (Finally):

Is it possible there is something wrong with my SynRod that is causing both Pump A and Pump B to fail?  My Pump A has not worked since I got my SynRod and my friend's Pump B fails every time I use it while he has no issues at all on his gun.  We have not tried my Pump A on his Marauder yet.

I got a Hill MK3 for Christmas.  I had to order a quick connect for the Marauder so I have not had a chance to use the new pump yet.  I am a bit hesitant because I do not want to blow the Hill pump with my SynRod if it has a problem.  I figured I would degass completely before filling with the MK3.

Any thoughts to this situation?

[Midwestairgunner]

You're filling a mrod vs. a disco. You are over working the pump and getting it too hot.

[Mark Mowrey]

You're filling a mrod vs. a disco. You are over working the pump and getting it too hot.

No, see the last bullet point and the line following. I sold my old Marauder to my friend.  He sold the Discovery. I left that part out.  The pump is not over heating. It doesn't have a chance to. His pump seems to fail on my SynRod shortly after the hose is pressurized, about 3-4 pumps after the guage on the gun starts to move.

[Mark Mowrey]

The pump is not over heating. It doesn't have a chance to.

My apologies.  Perhaps the pump overheating is causing the 007 o-ring to fail.  But the problem is that my friends Pump B works fine on his Marauder, but fails shortly after being pressurized on mine.  That is the question.  Is it possible there is something wrong with my SynRod that is causing the 007 o-ring to fail so quickly on the Pump B and my Pump A never working after multiples tear down sessions?

[Frank in Fairfield]

"The pump fails shortly after connecting to "MY" Marauder"

My question.

Who is pumping up your Marauder?

Let you friend do it and see if it fails.

I have two Benji Pumps.

One is 2.5 years old and has serviced two Marauders (sold them), 1701P, PRod and 1720T.

The other is a spare.

Pumping technique is very important.

Take your time, rest (cool the pump) after five minutes and, use your knees.

BTW the 2.5 year old Benji has never been serviced.

Tom Gaylord has a YouTube video I think...

[Mark Mowrey]

Who is pumping up your Marauder?

I am usually the one pumping my gun.  When he started, he was unaware of a "proper" technique and pumped as though he was filling a bike tire.  He has since learned to take deliberate strokes with pauses to avoid over heating.  I don't feel technique is the issue since he fills his Marauder with Pump B without issue and I filled it without issue using Pump A before I sold the gun to him. 

My concern is that there may be an issue with the fill assembly valve on my SynRod.  Could it get bound up somehow and cause the pump to work too hard?

[45Bravo]

You're filling a mrod vs. a disco. You are over working the pump and getting it too hot.

No, see the last bullet point and the line following. I sold my old Marauder to my friend.  He sold the Discovery. I left that part out.  The pump is not over heating. It doesn't have a chance to. His pump seems to fail on my SynRod shortly after the hose is pressurized, about 3-4 pumps after the guage on the gun starts to move.

How hard it is to pump before it fails?
What does the gauge on the pump say.

I don't THINK (I could be wrong) that that the fill assembly on the gun would have anything to do with the pump going bad. 

Not like it is in "infecting" the pump or anything.

I put a dead head in my hose after I service my benjamin pump, then pump it to 3000 (about 10 strokes) and let it sit for a minute to see if it leaks down.

Just like on the gun, it is easy to pump to 2500, after that it is hard.

On the rebuild you are just replacing 007?
Nothing else?

[Mark Mowrey]

How hard it is to pump before it fails?
It feels normal through the initial pressurizing phase (getting pump up to pressure of airgun).

What does the gauge on the pump say.
The gauge on the pump is close to what ever the gauge on the gun is at.  Fill points have generally been from 1800 psi to 2500 psi depending on SynRod's pressure at the time we got together.

I don't THINK (I could be wrong) that that the fill assembly on the gun would have anything to do with the pump going bad.
Questioning if it is possible that a stuck fill valve in the SynRod is causing the pump to work harder than it should.  Although, now that I think about it, that might show up as a higher pressure on the pumps gauge.  I don't recall seeing anything out of the ordinary. 

Not like it is in "infecting" the pump or anything.

I put a dead head in my hose after I service my benjamin pump, then pump it to 3000 (about 10 strokes) and let it sit for a minute to see if it leaks down.

Just like on the gun, it is easy to pump to 2500, after that it is hard.

On the rebuild you are just replacing 007?
Nothing else?
Yes, the 007 o-ring is shredded so just replacing that along with a wipe down of parts and lube with silicone grease.

I just had a feeling of Déjà vu.  Have I been here before???

[45Bravo]

As you came to figure, If there was an an obstruction, in the fill valve, it would indeed show as a spike in pressure on the pump gauge, that's why I asked.

I would on the next time you take it down, completely remove the steel rod that the 007 oring is on, and thoroughly clean and inspect the tube that the o ring runs in..

Just like you would do a rifle barrel.
Looking for corrosion, or other damage.

Since the oring keeps getting shredded, something there is doing it.

Before my last  servicing, I was hearing a "click" at the bottom of my stroke.
Turns out the brass piece that the oring is in, was coming unscrewed from the steel shaft.

In the last 2 times I have been into my benjamin pump I haven't had to replace the oring, just clean and lube that inner tube & shaft assembly(and this last time, put a dot of blue loctite on the brass head piece.)

Please keep us posted.