CEJN fitting strip-down

Hi greggabi - you can get them from Basecamp:

http://www.base-camp.co.uk/Optimus.html

Mike is away on his annual break but will be back in a few days - he will be able to sort you out.

 

Ah, Snowgoose got his reply in first. Makes sense to go for the Optimus spare, though as I noted in my original post I happened to have a Primus Omnifuel O-ring (part number 731905) - £2 from CCS Base Camp - that was also a fit.

John

 

What is the size on the o-rings in mm

 

@vargen77
I had reason to return to this thread to consult it for repair of a fitting and noticed your post. I recommend the 'Alert' feature on the site to make sure a question doesn't get overlooked as yours was.

I don't know the size of the O-ring, sorry. Approximately it's 6mm outer diameter and 3mm inner but there's no precision in my measurement. Primus Omnifuel O-ring (part number 731905) will work.

 

Ok thanks will check that out

 

O-ring size for CEJN from USA source:

McMaster-Carr
600 N County Line Rd
Elmhurst, IL 60126-2081
Chi.sales@mcmaster.com

I ordered the following:

Mil-Spec Fluorosilicone O-Ring, mil-R-25988/1-006

Many thanks to Presscall for his [usual] detailed photo-essay on how to dismantle an old style Optimus Nova pump with a CEJN fitting. I had used this stove on a backpacking trip to Rocky Mountain National Park this past summer. Towards the end of the trip I began to experience difficulty with the CEJN valve sticking "open" so that fuel would leak out of the filling. Searching the site for repair ideas I came across this thread. Presscall's suggested use of a Primus O-Ring and the accompanying photo made me think that the Primus O-Ring, in comparison to the Nova's CEJN O-Ring, looked similar in size to the O-Rings I purchased from McMaster-Carr to service my Coleman 222 lanterns. I finally had some time to fettle the fitting this evening. Dismantling the CEJN fitting and comparing its O-Rings with the McMaster-Carr O-Ring revealed a nearly perfect fit. Although the Nova's rings were intact and still pliable, I replace them nevertheless. Just fired the stove and it functions as it should. Perhaps it was the MSR mineral oil I slathered on the rings that restored operations to normal. In any event the stove runs fine with the O-Ring noted above.

McMaster-Carr's prices seemed reasonable and they shipped very quickly.

 

@NP4-8-4
I'm pleased your repair was successful and glad to have assisted with the write-up.

That's a really helpful reference for the O-ring source.

 

John, thank you for your thorough description of the CEJN strip down. I was wondering if you or anyone else had any technical data on the interior spring, the one that affects the o-ring seal so no fuel leaks from the fitting? Wire diameter, wire material, load, spring rate, length with no load, and solid length? Some or all of that information would be helpful in locating one.

 

@Tom Joad
Welcome to CCS. Sorry, I don’t have the technical spec for the spring in such detail. A search of the CEJN website or an email to their tech desk maybe?

John

 

Okay, I've located a spring that appears to have the right dimensions to fit inside the CEJN fitting. There doesn't seem to be enough room for all the bits to fit in the order you have them in, in the pictures you posted as I can't seem to press the last o-ring and the brass piece that first meets the male member past the retainer balls. I working with the following spring-

http://www.centuryspring.com/compression-spring-70664.html

 

Got the fitting assembled using some blue Nova o-rings that were somewhat smaller. I'll test it tomorrow and give a report.

 

@Tom Joad
Sounds promising. It’ll be good to hear your update.

 

@presscall

Hmmm. I tested the fitting using a dry run, meaning, I attached the pump body to the fuel bottle and the stove, then I pressurized the bottle. There were no leaks when everything was connected but there was a small leak when I disconnected the stove from the pump at the female part of the CEJN fitting. I disassembled it to find that the o-ring that has brass washers on both sides was torn. I tried with an original, unmarred o-ring and the same thing happened. O-rings were lubricated with the Optimus grease before assembly. I'm guessing there's a way to assemble so there's no o-ring marring but there's still the use induced tearing of the inner most o-ring to think about down the road.

That's been a common complaint with the CEJN, that it leaks fuel after you disconnect the stove. That did not happen to me for the duration of the time that I owned this, more than 15 years, until recently, and when I disassembled it I found the torn inner o-ring, however, I've never had leakage at the coupling while using the stove.

Now, some questions. The action of the coupling was smooth and the pressure required to connect and disconnect seemed about right. On the other hand, I don't remember which position the outer sleeve is in after removing the male part of the coupling: (i) in a position where the retaining clip is exposed or (ii) in a position where the outer sleeve covers the retaining clip? Knowing whether that outer sleeve is in the wrong position after disconnecting the male from the female part of the coupling will help me solve this problem.

The next question, is there a name for the brass part that's shaped somewhat like an arrow in side profile?

 

Last question first. I recognise your description of the part but don’t know the name of it.

Other Q’s, assuming my strip-down photos don’t help you arrive at the answers, some photos to illustrate what you’re saying would help. You’ll appreciate that it’s six years since I posted the original thread and haven’t had occasion to strip a fitting down in recent years.

John

 

I'll post pictures late today or tomorrow. Thanks for your help so far.

 

Your most welcome @Tom Joad. Sorry I couldn’t get my head around some answers to those latest queries.

John

 

@presscall Unexpectedly busy. I'll post pictures in a few days. Meanwhile I'm getting some more o-rings to fit and we'll go from there. Thank you.

 

Old Thread.
An added thank you @presscall for another well written post.

I see this:
McMaster-Carr
Still looking, but it looks promising. But, I have to create an account to buy less than 5 dollars of orings.

https://www.amazon.com/Fluorosilicone-Ring-Durometer-Blue-Pack/dp/B07R62T83Q
F70006 | Mr O-Ring

More later.
Ken

 

My teardown photo.
I know how to put it back together because of this thread. Thank you.
(2nd brass piece from the right, the 'cup', is backwards. Cup goes left not right.)

 

Glad it helped Ken. John