Leaking pump type fuel cap Svea 123. Need help.

Hi all. I’ve slowly been bringing this Svea 123 back to life. It came with the mini pump fuel cap. The cap was missing the pip and the seal for the SRV. I replaced the pip with the holder/pip/spring from The Fettle Box and used a 5mm Viton O-ring for the SRV. The issue I am having is that the SRV is leaking pressure almost all of the time and I do not know why. Was the o-ring a bad choice? Should I have used a flat seal instead? I have played with the tension on the set screw and it makes no difference. I would like to get this cap sorted out rather than replace it. I see no imperfections on the brass components where the pip and SRV o-ring seal at. Just to clarify, the leakage is through the pentagonal hole, not by the threads. The fuel cap to fount seal is new as well.
Thanks for any input. - Steve

 

Did you add the oring, does not sound original? The pip makes the seal.
Duane

 

Hiker Duane, there originally is a seal where I have the o-ring. It had disintegrated. The original seal was probably a flat seal and is not serviced. The caps for the mini pump use the pip and the SRV seal.

 

Kerophile, thanks for the link. I reviewed that before I redid the cap. I have it assembled correctly but am looking for thoughts on why it still leaks. Might the Viton o-ring be too stiff or too big?

 

Ok. Not all pips come out the same when punched out. I have to cull some when I buy them or try in another NRV. Make sure everything is lined up and not hanging up. Doesn't seem to take much for serviced NRV's to still leak. Rubber could also be too hard as you asked.
Duane

 

Both the size and stiffness of the O-ring and the tension of the springs also have to be correct for the pump to operate correctly.
Best Regards,
Kerophile.

 

Thanks to both of you. I think I will try a softer o-ring. The pip has a good imprint on it from the sealing surface when I unscrew the tube. I don’t care if the pump works good or not, I just want the cap to hold pressure.

 

The SRV spring is quite powerful, perfectly capable of making a seal with whatever’s offered up. A damaged O-ring or mating surfaces are more probable leak points than whatever elasticity/resistance the O-ring presents.

 

In my experience, many things to check to decipher where/what is/the leak. Have fun.
Duane

 

this seller on ebay sells a rebuild kit for the pump

NEW! MINI PUMP GASKET & SEAL KIT - FOR OPTIMUS MINI PUMP / SVEA 123 / PRIMUS | eBay

 

Thanks for the link on pump and cap rebuild kit but all of my seals are new. Will check mating surfaces with magnification for flaws.

 

Assemble, Dunk test, reassemble till it passes. A fickle assembly sometimes.

 

I just had it apart again. Took apart another (good) pump cap I have and compared the pressure created by the SRV spring. It is definitely a stronger spring on the good cap. I can’t remember exactly but I may have used some heat from a propane torch to burn out the old cap seal, etc.. Maybe I ruined the spring when doing so. I don’t see a source for a new spring so I guess I’ll seek out another cap. Don’t care if it’s pump-compatible or not. Trying to keep expense down as the stove was less than $5. I have 3 others so don’t really need it perfect but I enjoy the challenge of trying to make things work again!

Snwcampr: I was able to get a good dunk test on initial refurbish of cap but once the pump is used it unseats the pip temporarily. Can’t get it to seal consistently. I can put a piece of plastic tubing over the pip tube to block holes on side. Blowing on tubing I am getting bubbles/air out top of cap, no need to dunk test.

 

Maybe heat, quench, and temper it again.

Inconsistent? So it can work. Assembly seems key.

I only "need" them in winter, or to prime. To prime, pump, leak fuel into dish, replace with original cap, light.

Do you have a original cap?

 

No original cap. Just the pump and pump cap. This was basically a parts stove that I acquired with another complete one. The cap had no pip in it when I got it, you could see straight through the hexagonal hole on top into the pip tube. Maybe prior owner took apart to try and fix, gave up.

 

Things aren't staying lined up, hanging up too maybe? Spring or parts can catch, pip may not be staying 90 degrees to surface it seals onto, or spring may also be at a off angle. That oring not functioning properly?
Duane

 

@TSPORT

I would stretch the spring about 10-15% and try again.

Cheers

Tony

 

@kerophile
Were there pens that the spring was used for these pips?

@exeter_yak made springs.

 

Hi @snwcmpr . I would advise against any amateur making springs for a safety critical item such as an SRV. Such springs are made to material and dimensional specifications which we do not have access to.

Tread carefully.
Best Regards,
Kerophile.