I have an 80s vintage 123R. I have two caps, both about 5 years old or more, both purchased the same time; one used regularly and the other held in reserve. Earlier this spring, the stove wouldn't make good pressure with either cap, showing flame at the base of filler cap. I ordered and received replacement washers from the Fettlebox and replaced both. The stove is now making good pressure with the pristine cap, but it still won't make good pressure with the heavily used one. Again, both have new washers. Still, the heavily used cap is leaking at the threads. I can also add that neither cap will produce a flame at the safety outlet even if I hold a lighter to it. The only flame I get from the cap is at the bottom of the threads. 1) Could this simply be a bad washer? (I have more at home not with me that I could try) 2) Can a cap deform or wear with use to the point that a replacement washer isn't enough? 3) Could a failing pip (not replaced yet) cause flames at the thread? 4) Any other possibilities I'm missing?
If you're replacing the cap's viton washer you should probably replace the pip as well. The problem you're describing though is probably from a slight deformity in the the fuel cap, the lip of the tank's spout or the viton washer. When tightened the cap compresses one side of the o-ring to the lip of the tank's spout and against the top of the fuel cap on the other side. The threads don't provide a seal, they provide a means of holding the o-ring in place which creates the seal. Tightening the cap will typically compress the washer enough to seal it even with some minor deformities.
Check 1. the lip of the filler spout for damage. 2. the gasket has seated properly in the filler cap. 3. None of the old gasket is still stuck in the filler cap causing a lump.
Thanks all for the help. Could an errant grain of sand be the cause? I removed the washer from the leaking cap, cleaned out the cap extra well, flipped the washer over and reinstalled it. I'm in a sandy location at present and suspect a bit of sand got in? Test fired the stove and it came up to full throttle no problem. Flame tested the cap several time throughout the burn and got no indications of a leak. Perhaps a dunk test is in order to double check? If so, is this the right order? 1) Empty the fuel and let dry. 2) Remove cap and burner bell and put stove in freezer to chill. 3) Heat water to boiling in large pot. 4) Put cap on and dunk stove to check for leaks.
I suspect that you fixed it. It does not require that the stove be frozen, just cold. Water does not have to be boiling, just hot. The hot water will increase the pressure of the tank and it will have to go somewhere if there is an opening. The idea is to see where the leak is, not a full blown pressure test. But, that would be useful another day.
So, I dunk tested the stove today. Is it common/correct for the pip to pip, pip, pip out a very slow set of bubbles? I get no indication of a leak from the pip when the stove is running.
