I have an Ultimus two burner stove that is, I think, about a 4 pinter. It was in good order but I have gently cleaned it, replaced the pump washer and all seals including the NRV set with new (from Fettle Box) and fitted new jets. My problem is I can't seem to get any pressure in it. The pump washer is a good fit but 100 pumps don't seem to produce any pressure in the tank. I've submerged the tank and no bubbles. I've swapped the NRV for one that works in an Optimus 00. Still nothing. Curiously, if I remove the NRV and push the pump in I get a bubble out of the jets. I'm wondering whether it's just because the tank is so large?? Will it pressurise when I fire up the meths? I wonder whether to fit a schraeder valve to a spare filler cap and pressurise it with a bike pump to see if there's any leaks (but dunking it makes that seem unlikely). Ideas...
Not familiar with this stove, but a recent post on CCS pointed out that many of these pumps rely on a level of "slop" between the pump cup and shaft - the intake air goes between the pump shaft and cup. Sometimes a pump has been "fixed" (no slop) and consequently does not work. Unlikely but a little something to check. Norm
No need to rig a special cap to use a bike pump. Just buy a valve stem from the auto stuff store. Remove the pump from the stove, hold the bulb end of the stem against the opening and pump (easier if you have 3 hands, but it can be done with two). If the check valve is working you should rapidly build pressure. Don't over do it. If the pump tube is big enough the bulb end may even fit tightly into the opening.
Thanks for the advice. I've renewed the pump cup/washer and it almost seems as if it is working on the up stroke and not the down stroke - so it may be that there is no air being allowed in to compress on the downstroke. I'll play around and see what I can do.
