Air Gun Home :: View topic - Benjamin Marauder Pistor Empty after a few hours

MikeSD · Member

I just got a Benjamin Marauder pistol. Looks nice.

However, I filled it to around 2900 psi, fired 2 shots and the pressure was a little below 2900.

Then, I put it aside to see how long the air would stay in the pistol. 12 hours later the pressure was at about 200 psi (in the red). The gun almost completely bled out. Is this normal? Should the gun leak to the point of becoming virtually empty after 12 hours?

I'm thinking not since the people at Pyramid said to not run the gun to empty and store it with at least 1000 psi in it. But what have others experienced with regards to this pistol retainin the air, once filled?

Thanks,
Mike

SMP · Silver Status Member

Sounds like there may be a spec of dirt on the valve. Try filling it and shooting it down to dislodge the dirt and seat the valve

If that doesn't work you have two options.

1) send it back

2) strip it down and clean the valve/replace the seal

Here is an exploded diagram. As you can see the valve is not that complicated

http://www.crosman.com/pdf/manuals/1763%20and%202263%20EVP%20and%20PL%20Update%20II.pdf

Edit: Replaced bad link

MikeSD · Member

SMP · Silver Status Member

Sorry about that...I thought I pasted the location on crosman's site.

http://www.crosman.com/pdf/manuals/1763%20and%202263%20EVP%20and%20PL%20Update%20II.pdf

That should work a little better

3) Fairly common that the valve needs to do a little work before it fully seats.

4) Yes I would send it back PDQ!

MikeSD · Member

oddtodd · Silver Status Member

Personally I wouldn't crack it open. I would just leat pyramyd to replace it. I know you will be down a little time, but it's better than not having any warranty if something really goes wonky with it.

SMP · Silver Status Member

Pulling a valve is not complicated and requires no special tools.

First thing I would do though is fill it and put as many shots through it as I could one after another.

One very important thing is keep all oils or greases out of that tube. They will exploded.

Only pure silicone grease is acceptable in a pcp tube. eg divers grease.

One of the other members will likely be along and give you a step by step if you really want to pull it down

MikeSD · Member

Looking at the exploded view of the rifle (I have the pistol version), it looks like:

1) The nipple adapter screws into the
2) Housing adapter which butts up against
3) the guage port which butts up against the
4) valve assembly

There are a few places that air might escape. At the opening in the adapter itself and at the o-ring seals. It should be easy enough, using some soapy water, to see if the leak is in any of these ares, without any disassembly.

The other place where there might be pressure loss is at the point where the guage screws into the tube. That should be easy to check, also using the soapy water trick.

The other place is at the valve itself. That would require some disassembly I think.

There is one other thing I'm wondering about. There are 3 main components in this pressure path, before the cylinder (pressure tube). 1) The adapter and housing, 2) the guage port and 3) the valve assembly.

There is definitely high pressure, within these three components. But there are o-rings that appear to be on the exterior of these, rather than on the ends where they could seal the air. What are these o-rings for? Since they are on the exterior surface, they don't appear to be high pressure seals. It's hard to tell from the exploded view.

And, regarding these 3 components. Do they just butt up against each other or do they screw into the other components? What keeps the air from escaping between these components? I would think it might be the o-rings but from the diagram, these o-rings don't look like they are on the ends, between these components. They look like they are in groves on the exterior surfaces and don't make contact between these 3 components. I guess if I had it apart, it would be obvious.

The last thing I need to know, if I should delve into this is, will I need any thread locker goop or any other silicone grease or can I count on what is already there to reseal everything. I guess this thread locker shouldn't have any high pressure, if the o-rings do their job.

Mike

SMP · Silver Status Member

MikeSD · Member

Ah! I see. It wasn't so obvious by the exploded view. Your explanation helps greatly. I guess I should have noticed that the valve goes to the far end of the tube. Duh! It almost looked like those three components were butted up against each other. But in reality it's like this (confirm):

1) The adapter housing seals the end of the cylinder, with the o-ring. The threads in the housing should see no pressure.

2) The guage port is only to allow the guage to screw into something and the o-rings on either side, merely seal the air from bypassing the port component. Guage measures air in the interior of the port component, which is the same as the cylinder pressure.

3) Finally, the valve is at the far end of the tube, and the only exit of the pressure is through the muzzle, via the valve opening. The o-ring again there, just seals the air from exiting out the back of the gun, through the screw holes.

4) It looks like the adapter housing can just be unscrewed from the front, without removing any other screws.

5) It looks like the guage port can be removed by removing the guage and adapter, then (I guess) pulling it out from the front. But it must have a friction fit, because of the o-rings. How would one reach it to get it out? I doubt it's gonna fall right out.

You say there should be no pressure at the screws on the guage but there is an o-ring on the adapter. So if it's not secure, might there be a leak there?

6) Finally, the valve looks like it will take a much more detailed stripping of the gun, to remove it. Right? It looks like it might have screws in it. Can it be removed by removing the back pressure cap and hammer component without removing the trigger assembly or stock?

I guess I'll find out tomorrow, after I do my bubble tests. Wink

Thanks,
Mike

SMP · Silver Status Member

1) correct

2) correct

3) correct

4) correct

5)correct. You push it from the rear

5.1) There is no pressure at those screws. They are in shear from the force on the face of the valve applied by the pressure

6) Yes unfortunately you pretty much have to disassemble the entire gun. That odd screw entering the valve is the orifice adjusting screw.

It's not all grim though. I have some experience but I can have any gun I own valve out in 15 minutes.

First time through will take a lot longer but that gives you an idea