Scubapro G250: strange free flow

[Zung]

Yes I have.

Popper-wise, the history is:

• Current s-wing poppet #1: free flow
• Current s-wing poppet #2: free flow

Now I swap in the older single o-ring poppet, the one on top

And the free flow has stopped for the last couple of hours.
If it stays put, it's yet another strange cas of poppet/lever compatibility.

I leave it on for a while and report back if there's any change.

Edit
I also swapped back the current lever, like the [-]right[/-] left one in couv's pic:



So now it has an older poppet and a current lever.

Edit
12 hours later, still no free flow.

 

[Zung]

24 hours after, the thing still behaves, no free flow, and the cracking pressure is just above 25 mm / 1", with a lightly used seat: good enough for a backup set.

To sum it up: the only combination that works is the current lever with an older single o-ring balanced poppet.

Why? I really don't know.

 

[Texfrazer]

Here's a really "out there" thought, but since you've tried so much else.

It looks like the right-most o-ring on your new poppet is notable larger than either of the other ones. I know that it's there as a "wiper", but that may be catching just a little in the balance chamber and not allowing the poppet to completely return to it's original position.

If you want to see, just pop that right-most o-ring off and reinstall the new poppet with only a single o-ring.

 

[redacted]

Here's a really "out there" thought, but since you've tried so much else.

It looks like the right-most o-ring on your new poppet is notable larger than either of the other ones. I know that it's there as a "wiper", but that may be catching just a little in the balance chamber and not allowing the poppet to completely return to it's original position.

If you want to see, just pop that right-most o-ring off and reinstall the new poppet with only a single o-ring.

Good eye. But that is a designed difference in the depth of the 2 glands. The wiper o-ring sits in a deeper gland - probably for less friction since seal is not required.

What I don't understand is, even with the lever a bit too high, you should be able to stop the leak with just a small adjustment of the orifice after the cover is installed. Another idea - try swapping out the diaphragm. Maybe you have a 95th percentile lever and a 5th percentile diaphragm.

 

[Couv]

Good eye is right. But it seems things are a bit backwards. The o-ring that goes deepest into the balance chamber is the primary o-ring and should be the one without much play in it as the groove is not cut as deep. The other o-ring serves as the wiper and should have a bit more play in it than the primary. Looking back on this thread to confirm, http://www.scubaboard.com/forums/repairing-your-own-gear/315241-scuba-pro-s-wing-poppet-o-ring.html the primary o-ring groove is approx 0.091 inches and the wiper groove approx 0.077 However, I don't think that's the problem because you've tried at least 2 poppets. The next thing I would try has been suggested by Herman....the balance chamber. It may not be the problem, but it certainly is easy enough to replace. If I recall correctly, the G250 has a anti-friction ring that goes between the cover and the diaphragm; I trust you remembered to reinstall it. Also, sometimes you just can't get away without a break in period. One way to accelerate the break in period is to "de-tune" the second stage overnight by purposely (and purposefully) adjusting the orifice in 1/2 turn or more than necessary and let it sit overnight, then make your final adjustment.

But my money goes on the lever. Mainly because the problem goes away when you remove the cover. One question. I was given to understand that (looking back at the picture in post #11) the levers are arranged newest to oldest-left to right? Is that not correct? I've had the best luck with lever #1 combined with the s-wing poppet.

Now, if you really want to make us happy, you'll start all over again with the first set of parts placed in a different G250. An old avionics instructor I had would claim, "To do proper troubleshooting, you have to convict the bad part!"

 

[Zung]

Thanks for the TLC Gents, but I haven't been entirely clears, so here's some more answer, by order of appearance of the questions:

• Good Eye: sorry, it's a "stock" photo, one I uploaded previously, just to make sure what I meant by "single o-ring balanced poppet". The real ones are not that different.
• awap: yes, I did tried swapping the diaphragm (twice), no change
• Herman/couv: I did swap the balance chamber along with the poppet. Actually, I just pulled the whole thing (poppet/chamber/o-rings/seat/spring) out of a maintenance kit
• couv: break-in: I did let the reg sit for a week before doing anything
• couv: sorry, my bad, I said the rightest lever when I meant the leftest/newest lever. I corrected my post
• couv: doing it all over with another G250 body: I may just do that: no snow in the Alps, no ski, and plenty of time weekends. But first, I need to talk some sense into my LDS so he agrees to fill my tank which is barely 2 years overdue for hydro

One additional clue: by feel, there's a "rough" spot in the beginning of the travel of the lever with the newer s-wing poppets. Nothing drastic, but there's some kind of a step when I press the lever down. I guess it's some roughness in the square holes of the barrel.

 

[LeadTurn_SD]

Dear Board,

I have a strange behavior in a SP G250: when I turn the air on, initially, everything is fine. But after a few breaths, it starts freeflowing slightly, a small hiss. I turn the adjustment knob in maybe half a turn, it stops. After a few more breaths, it free flows again, somewhat less than before, but still noticeable. And this goes on.

First I think maybe the poppet has a problem, replace the whole assembly: poppet+ seat + balance chamber + spring. Same thing. Then I replace the orifice. Still the same.

I don't have anymore part to throw at it. What can it be?

I think you've already gotten good answers from the masters.... here are the pupil's thoughts:

The rough feel you describe at the beginning of the levers travel, and the fact that initially you have an "air seal", but then a leak after breathing the reg seems to point to the poppet not moving all the way back into position. Tightening the knob puts some more pressure on it, shoving it back into place, stopping the leak... but then breathing it again eventually reproduces the leak.

If the lever was too high, turning in the orifice would correct that (eventually), but maybe at too high a cracking pressure. That was the problem I was trying to diagnose and fix with my 1st -109.

I have also felt some roughness in the initial travel of the lever on my first -109... I think I know exactly what you are describing and it went away with some fiddling... a good outcome but bad in that I don't know WHY or HOW it was fixed, so I don't know what caused it... it just got better. Bad for the reasons couv mentioned about "proper trouble-shooting".

I could not tell if it was friction, or the spring binding.... it just felt like a rough "step" the first few mm of travel, then normal and much smoother travel thereafter.

So: The lever is involved, but perhaps not lever height, rather lever "action"? Could the lever be "sticking" just slightly in the open position (or the poppet causing the lever to stick, or both)?

Sorry, think I just ended up repeating what was already mentioned.

Best wishes.

 

[Zung]

Thanks LTSD, but you really should look into your membership standing/membership fees issue: you still don't have a "Thanks" button!

 

[redacted]

Double post.

 

[redacted]

It seems to me a rough spot should be there regardless of whether the cover is installed or not. I think I would try changing the geometry a bit by removing the clip on the adjustment knob, back it off a quarter turn or so and readjust the orifice. That should bring the lever height down a bit. If that has no effect, I'd tend to exclude a lever height problem. If that does correct the problem, I'd probably have to play with it a bit more. Measure lever heights and see if that makes sense. You could modify the clip (flatten the limiting surface) and leave it that way. I found some brass rid stock that I made some clips at one time which would be easier to work with. Or fashion your own stop from some copper wire.

I think it warrants a bit more troubleshooting including couv's suggestion of installing suspect parts in a working G250. Or just put it back in the spares bin and use another 2nd.

Can you stop the leak by jarring the reg a bit? If the poppet or lever is catching on something, that may break it loose and stop the leak. I'm not sure how you would isolate the offending surface, so you might just have to do a little polishing and re-try. Have you tried a different inlet tube yet?