I've had this particular valve cap for a mini-pump for a little over a year. I use it on an 8R. It has always worked fine. Lately it started sticking; took a bit of extra effort at the end of the pump stroke to get it to open up and blow. Then, suddenly, it got too easy. Very little effort is required for the pump stroke. Experimenting with a lit stove shows that it is working -- you can see the flame vary in intensity with the stroke. But -- here's the catch -- it will no longer hold pressure. You pump it 2-3 times, get a nice flame, but within 5 seconds that flame is struggling to survive because there is not enough pressure in the tank. If I pump it, remove the pump, and put my thumb over the hole, it holds pressure just fine. Is it possible to just replace the spring? Or do I need to get a whole new cap? Anyone had this happen to them? Obviously, I have removed it from service. There has to be some amount of gasoline fumes coming out of the hole, that close to an open flame; strikes me as a bad idea.
Ace hardware I believe sells springs or you can use a ballpoint pen spring but need to adjust it to the right tension. Sticking may be due to bloated rubber. Had the same problem and replaced the rubber on it and not the spring. RON
I´ll fill in with another question about the valve cap.. Which cap is the tight one, the one that is rounded, or the flat one? I mean, one cap is a little rounded, with what i think I remember as a hexagonal screw, and the other is a round flat top with a groove across, like a flat screw, with a brassy "thingie" in the middle. Regards Ulf
Hi Ulf, To use an optional mini or midi pump on an Optimus gasoline stove, you must first replace the existing filler cap, with a special cap, to which the pump can be connected. The replacement cap is ingenious as it still operates as a safety pressure-release valve, yet contains a non-return valve for the pumping operation: https://classiccampstoves.com/threads/optimus-199-help.5518/page-2#post-49205 Best Regards, Kerophile.
Kero, I have had 2-new midi pump caps do this. I unscrewed the brass lower pip assy. and stretched the spring oh so slightly. It was hard at first to put in some pressure, but loosened up. One of mine did look as though the pip was hanging a bit in one of the inner vent holes. looked as though there was a slight taper to the stopper. AR
Hello, This picture might help On the left are two filler pump caps and a mini pump. On the top right is a standard filler cap. Jeff
Breramold, the rubber stopper should move freely within the tube as I noticed mine did not and sometimes gets lodge when I start pumping hence the loss in pressure. A new well rounded stopper should do the trick. Yup you will have a difficult time pumping if you stretch out the spring too much. Ron
I gave the spring a bit of a stretch and that seems to have solved the problem. It is harder to pump than it was before, but I expect that will settle in like anlrolfe's did. It's not sticking like it was a few days ago, just takes more pressure to pump. I wonder if there was just a wee bit of roughness catching in one of the "windows", and when I put it back in, that patch lined up with the walls instead of window? Who knows. So fine to get good advice so quickly from so many knowledgeable stovies. Thanks guys for the tips and pix.
Hi, this thread contains a post by Aktopp, which provides the best description I have seen of the construction and means of operation of the Optimus pump-cap: https://classiccampstoves.com/threads/optimus-199-help.5518/page-3#post-49214 Best Regards, Kerophile.
