sudden depressurization

[Roland the Headless...]

 I have a 1st gen. Marauder, .25. No modifications, no tuning. The rifle has not been tinkered with since it left the factory. I hadn't shot it for about a month, and I broke it out this evening. I noticed that it had depressurized. Seemed odd, this had never happened before, to this or any of my other PCP's. I refilled to about 2600K, checking for obvious leaks-none detected. I loaded a magazine and ran off five rounds. All seemed well, so I ran off five more. So far, so good. Then I refilled to 2600 again. After firing the thirteenth round the rifle depressurized. I could hear air rushing out of the end of the barrel, and upon opening the breech, both ends of the barrel. Took about two minutes to completely depressurize. I'm hoping this is a minor issue, with a simple fix (sticky valve, O-ring replacement). I'm no airgunsmith, but fairly mechanically inclined. Any body have ideas on where to start looking? I thank you in advance.

[Motorhead]

If release of pressure was indeed OUT THE BARREL ... this predisposes a valve system failure that could be a sticky poppet valve or failure of the poppet valve itself ?

All your primary tube o-rings are SAE # 118 buna ... poppet valve a Crosman part with no alternative currently I'm aware of.

Have fun !

[Roland the Headless...]

 Thanks for the quick response. In studying the exploded diagram, I see no "poppet" valve. Would this be the valve assembly, item #2, On Crosman's diagram?

Tried to link it but the software won't allow me to post external links.

[sixshootertexan]

Correct item #2 is the valve. Look at the exploded view of the valve the poppet is item #2C.

[Ribbonstone]

Good news: it's an inexpensive part

Bad news:  Almost full disassembly to get to it (you won't have to take the trigger unit apart, but that's about all).

Odd that it doesn't leak all the time....which might be a sticking issue rather than an actual broken/leaking stem.

got nothing to lose by this: Won't hurt to fill it and dry fire it (fire with no pellet) a couple of dozen times.  Jeah, that's loud...and it moves a lot more air than firing with a pellet.  Would give the valve a few more cycles (incase it's sticking on the valve stem shaft) and blast more air though the valve per shot in case there is anything fouling the valve stem than can be air-blasted out.

[Roland the Headless...]

Good news: it's an inexpensive part

Bad news:  Almost full disassembly to get to it (you won't have to take the trigger unit apart, but that's about all).

Odd that it doesn't leak all the time....which might be a sticking issue rather than an actual broken/leaking stem.

got nothing to lose by this: Won't hurt to fill it and dry fire it (fire with no pellet) a couple of dozen times.  Jeah, that's loud...and it moves a lot more air than firing with a pellet.  Would give the valve a few more cycles (incase it's sticking on the valve stem shaft) and blast more air though the valve per shot in case there is anything fouling the valve stem than can be air-blasted out.

 Just tried that, won't hold air at all now. Just hear air escaping out of the barrel as I pump. Also, something is rattling inside the reservoir. I can hear it rolling from end to end. Sounds plasticky.