My Benjamin Marauder is loosing power. What may be the cause of this?

[Earl]

On 7-1-2019 Marauder was shooting 102 good shots from 2950 to 1650 at 782 fps average with AA 10.3 gr.
On 12-28-2019 Marauder shot good groups at 49 yards so I assume the velocity was still 782 fps with AA 10.3 gr.
On 10-2-2020 Marauder shot very low at 28 yards with AA 10.3 gr so I assume the velocity was dropping.
On 11-21-2020 Marauder shot at 492 fps gauge at 2400 psi with AA 10.3 gr.
On 11-23-2020 Marauder shot 390 fps average gauge at 2300 psi with AA 10.3 gr.
The Marauder's settings from 7-1-2019 to 11-23-2020 are:
Spring is 1.75 turns in from stop.
Striker is 9.0 turns in from stop.
Valve is 1.5 turns out from stop.

[AlanMcD]

Have you confirmed that the hammer spring and striker settings have not changed?  They have been known to walk over time on some guns.  If not, it sounds like maybe your spring adjuster has backed out, reducing hammer energy, at least as one option.

[Ribbonstone]

Usual suspects:  The adjusments un-adjusted. Something is blocking the striker's travel.  The poppet is deformed/compressed.

One odd one that has happened to me: the gauge is lying.  HAve one that somehow broke and reads 2200psi even when the gauge is off the rifle.

[Earl]

Usual suspects:  The adjusments un-adjusted. Something is blocking the striker's travel.  The poppet is deformed/compressed.

One odd one that has happened to me: the gauge is lying.  HAve one that somehow broke and reads 2200psi even when the gauge is off the rifle.

I checked the gauge by connecting a hand pump to the Marauder and pumping up to 2300 psi and then the Marauder started taking air.
So the gauge is working.
I checked the adjustments.
Spring is still at 1.75 turns in from stop.
Striker is still 9.0 turns in from stop.
I do not know how to check if "Something is blocking the striker's travel" or "The poppet is deformed/compressed."

[Hobbyman2007]

Did you by chance add a regulator to this gun? It could be regulator creep . If not , I’d be looking at the hammer and/ or striker adjustments as mentioned before.

[Earl]

Did you by chance add a regulator to this gun? It could be regulator creep . If not , I’d be looking at the hammer and/ or striker adjustments as mentioned before.

I did not add a regulator.
"the hammer and/ or striker adjustments as mentioned before." They are still the same(1.75 and 9.0 turns in from stop).

[kbstingwing]

do the tissue test at the breech, maybe the O-ring is leaking or blown out.

[sb327]

Could the hammer area have gotten oiled? And now it’s a little gummy? And the cooler temps exaggerated the effect?

I’ve only read on here that that can cause problems.

That and possibly a stem poking through a poppet.

Or possible the tport adjustment?

Just throwing out ideas.

Dave

[Earl]

do the tissue test at the breech, maybe the O-ring is leaking or blown out.

I have done the tissue test with the single shot tray and the tissue did not move.

[Earl]

Could the hammer area have gotten oiled? And now it’s a little gummy? And the cooler temps exaggerated the effect?

I’ve only read on here that that can cause problems.

That and possibly a stem poking through a poppet.

Or possible the tport adjustment?

Just throwing out ideas.

Dave

I shoot inside so the summer temperature is about 76 and the winter temperature is about 72 degrees F so that should not be a problem.
I do not know how to check "possibly a stem poking through a poppet."
I will check the transfer port adjustment(valve metering screw).

[triggertreat]

I would recheck the valve metering screw (brass screw).  When you screw the second plug back in on top of it, it can turn the metering screw back in with it if not careful.  You could open that screw CCW some more and that should increase your velocity.  1.5 turns out is pretty closed off.

Things can change over time with the spring tension as well, especially if the hammer has gummed up.  Try turning the hammer adjustment in more CW, or the striker CCW for more stroke length to see.  The striker can move on you while shooting if loose.  This is also very common and will change your tune.

It could also be the valve's poppet that is attached to the pin the hammer strikes that is on the inside of the valve depending on the age of it.  It could very well be breaking down and mushrooming causing the striker pin to change the distance it use to protrude towards the hammer striker, or causing the poppet itself not to open as far as it use to.  That's about all it could be.  It's one of those.  It's a pretty simple system.  If the transfer port O-rings are good and the breech O-ring is good those won't let any air past them either while shooting to drop the velocity. Is the gun louder than before. that's a good indicator one of those are missing or loosing air from a bad seal.

[Earl]

triggertreat,
I put tissue paper over the breach and no air moved it when I shot the gun with the single shot tray.
Where should I put the tissue paper to see if the transfer port o-rings are leaking?
The gun is not louder when shooting.

triggertreat said,"It could also be the valve's poppet that is attached to the pin the hammer strikes that is on the inside of the valve depending on the age of it.  It could very well be breaking down and mushrooming causing the striker pin to change the distance it use to protrude towards the hammer striker, or causing the poppet itself not to open as far as it use to."
Is there a youtube video showing me how to check this?
The sn is 114121737.  I got the gun from Amazon on 9-1-2015.  It has not been shot a lot because it is not one of my favorites.

[triggertreat]

triggertreat,
I put tissue paper over the breach and no air moved it when I shot the gun with the single shot tray.
Where should I put the tissue paper to see if the transfer port o-rings are leaking?
The gun is not louder when shooting.

triggertreat said,"It could also be the valve's poppet that is attached to the pin the hammer strikes that is on the inside of the valve depending on the age of it.  It could very well be breaking down and mushrooming causing the striker pin to change the distance it use to protrude towards the hammer striker, or causing the poppet itself not to open as far as it use to."
Is there a youtube video showing me how to check this?
The sn is 114121737.  I got the gun from Amazon on 9-1-2015.  It has not been shot a lot because it is not one of my favorites.

I do believe there are videos showing the breakdown inside the Marauder.  You just have to type in Marauder in the search and see what pops up.

[FuzzyGrub]

Your striker adjustment seems excessive at 9 turns out.  You can try adjusting to zero turn, to see what you get. 

Assuming you didn't shoot it much between 11/21 and 11/23, but still had a 100fps drop, leaning that it is not adjustment creep.

You gun was mfg Jan 2014, so the poppet could be deteriating.  There have been some photos posted by GTA members on that.  You will not be able to diagnois without a full dis-assembly. 

[Earl]

If the poppet is bad;
What parts should I order?
Where should I order them from?

If I want an experienced person to do the work;
Where do I send the Marauder for repairs?

I have successfully replaced the o-rings in a Discovery by watching a video.
Does that make me qualified to change a Marauder poppet?

[FuzzyGrub]

To an extent, the mrod is a similar design as the disco.  It shouldn't be any harder, and there are some videos out there.  The valve only consists of unscrewing the front and removing spring and poppet.   The poppet is only $2 from crosman + $4 shipping for small parts order.  You will need O-rings, but I'd wait until you have it tore down, so you have a complete list.  There is a possibility there is corrosion in the valve, and that is around $25 from crosman.

[vdwb]

Earl,
If you’ve done disco o ring replacement you should have no problems with your Mrod. Just picture a large version of your disco, pretty much the same. I would order the poppet from eBay or Crosman and the -118 duro 70 o rings from wherever. The challenge is getting the valve and 1/2 of the gauge block o rings past the gauge port hole in the tube without cutting them. I have a tool for that.
Dennis

[Earl]

When I checked the valve screw, it may have been at 0.0 turns in.
As soon as the wrench seated, it did not seem like the screw moved at all.
The last time I adjusted the valve screw, it was 1.5 turns out.
The problem was, the valve screw was getting TIGHTER as I was shooting.
The valve screw is VERY loose.
I used Vibra-tite on the valve screw but the screw was still loose.
I put Locktite low strength on the valve screw and will let it dry to see if the valve screw tightens up.

[triggertreat]

Glad to read you were able to get it sorted out Earl!

[FuzzyGrub]

Glad to read you were able to get it sorted out Earl!

Yes, and much simpler than a dis-assembly/reseal.      Glad it was something easy.