Hi, Has anyone had to deal with an erratically pulsing stove? My Nova has been doing this for the past while and I'm really confused as to what's causing it. Initially I thought I had an air leak between the pump body and the fuel dip line so put a bead of glue around the join. That didn't seem to help and I've also run it with the bottle tipped upward slightly to ensure everything is completely submerged. Still no luck. The fuel is fresh Aspen and I've completely cleaned out the bottle with soapy water and thoroughly dried it between emptying the old fuel and adding the new. The inline filter is also new. It's strange. It almost sounds like the cleaning needle is rattling around in the stove or something. You can hear it if you listen carefully to the second of the three videos below. The last video is where I tilted the fuel bottle slightly. Does anyone have any suggestions as to what could be causing it? I'm pretty sure I've ruled out contaminated fuel and air in the line so now I'm puzzled. Thanks, -M
Have you tried to reduce the amount of air pressure you put into the bottle? I found with my Nova+ and Polaris that they can be somewhat sensitive to too much air pressure and being throttled down. By leaving the pressure lower initially during preheat and the thermal soak period then pumping the pressure up a bit before throttling back from full I found they don't pulsate or pulsate in a readily noticeable manner. How much pressure is in the bottle depends on how much air space there is, with a bottle with a lot of fuel 2-3 pumps often is a lot whereas when the bottle is almost empty I find that I need 10-20 pumps to even get similar output when the valve is wide open. Here's a thread on pressure: New Optimus Nova w/ white gas - Flame pulsing and boil time normal? You may want to check changing your jet as well: Is This Optimus Polaris Working Correctly?
In the videos I linked with a full fuel bottle I think I was running about 10 pumps. That got me about as much power as I'd feel comfortable with in my trangia but definitely less than what I've used it at in the past with regular pots and it didn't fluctuate the same way. Any lower pressure and I feel like I'd be sacrificing power quite a bit. Regarding the linked threads, I'm pretty sure what I'm experiencing is different to that. I've encountered the "helicopter" chuffing before as well and it was very dependant on pot height as well as throttle whereas the erratic pulsing I'm getting at the moment is much slower, randomly timed and doesn't vary much with or without a pot or depending on throttle. Towards the end of the third video where the flames are completely laminar (minus the flares) I don't think you'd end up with that sort of resonance either.
@_monk_ Ten pumps is nothing. Pressurize the bottle to the normal extent and throttle down, or discontinue using the Nova in a Trangia if you’re fearful of overpowering it. A Trangia 27 is pushing it, the 25 gives more clearance and heat sink margin. I don’t see there’s a ‘magic bullet’ to resolve it otherwise.
Try using 1-3 pumps at first, let it warm up then open the valve up all the way before adding your additional pumps to the point you feel comfortable for power output.
So more pumps while simultaneously fewer? I'll have to break out my quantum pump to get a superposition of the two. I can give it another go but I've already tried the obvious permutations of pumping pressure when it originally started playing up and didn't really get anywhere. It affected how violently it pulsed and also the average space of time between them but it was equally erratic. It seems quite different from the helicopter sound that other users have reported with this stove (which I've experienced in the past). Regarding using it in my trangia, I'm aware of the limitations of using it in a 27 and don't mind running it on a lower power compared to if I use it in the original base. However I would like it to function properly in the mean time so I don't have to worry about it snuffing itself out. Besides, it behaves exactly the same if I run it in the original pot stand anyway.
I would just give it 1-2 pumps from a full bottle so there's enough pressure to push fuel out and let it heat up before opening the valve fully. From there just keep the valve open and continue to pressurize the bottle until you get the output you desire. What I have found with my Polaris and Nova+ is that it doesn't pulsate (or "chuff" to my ears as I think of it) when the valve is wide open and the pressure in the bottle is relatively low. My personal theory is that the fuel (rapidly) vaporizes and creates back pressure in the spindle, which causes fluid flow to briefly stall out. Once the pocket of gaseous fuel makes it out of the jet then flow resumes but rapidly so which causes another slug of fuel to rush into the hot spindle before it rapidly vaporizes. By opening the valve fully there is very little obstruction for the liquid fuel to make it out and by reducing pressure there is less of an "air spring" for the fuel to oscillate from. By using bottle pressure as the limiting factor then the fuel flow is effectively only restricted by the bottle side. I have experienced similar effects on an Primus Omnilite Ti, which was caused by clogged filters that led to using high pressure in the fuel bottle. What I found out was that by using the valve on the pump end (technically stove fuel hose end) rather than on the stove spindle then the pulsations could be reduced but changing the filter, reducing bottle side pressure and "choking" the flow a little on the bottle if it was still present would eliminate it.
Assuming you have done the standard cleaning of valve and fuel line? Acts like a blockage. Using the new brass filter?
I did have a similar thought regarding fuel flow in that it almost seems like a "drip drip" type of thing but thought it was too remote to investigate further until I'd eliminated other possibilities. What would that involve? I've done the basics like brushing down the threads on the spindle but nothing more dramatic as it never looked particularly crusty. It has dark patina to it but that's about all. I can't comment on what the inside of the spindle tube is like though. I used to mainly run it on paraffin or Primus fuel but I doubt I've run more than 5 litres through it so never thought it might need a deeper clean. Here's a photo of my valve spindle.
A quick addition as it's too late to edit my previous post: The only other fuels I've ever used were when I tried to run it on methylated spirit once out of curiosity (failure as expected), the same experiment but with turpentine substitute (it burns but it's not ideal) and lastly when I hooked it up to a gas canister a couple of times. Additionally the "paraffin" I used at one point was bought from French supermarket and advertised for lantern use but it smelt and performed exactly like the regular stuff so I don't think it was anything like the heavier "lamp oil" you sometimes hear about.
Did it start pulsing after you used the alternative fuels? Yes? Then run some clean fuel through it, hot, and see if it improves.
Well technically yes, but it saw me through a week long cycle tour between then and now running on paraffin without issue. I'd estimate I tried the alternative fuels almost ten years ago now so I was mainly mentioning it to be thorough. Since then I've only used paraffin or naptha equivalents.
I had an issue with excess silicon grease inside my new Nova years ago. It was intermittently restricting fuel flow and exhibited irractic performance. Needless to say, it was very aggravating problem.
Cannot remember was there a fuel filter also in joint where fuel hose mounts to stove. If there is change of that fuel filter might help. Also it might be a good idea to remove spindle, jet and cleaning needle. Clean them, stiff fuel tube and 'chamber' where cleaning needle normally sits/is. Jet should be cleaned from inside also since time to time some dirt&soot accumulates there.
