So I've decided to take the leap into trying out coil stoves and recently picked up a Stesco in very good condition. It looks like it had only been test-fired once or twice. The windshield was still wrapped up in the paper packing. I fired it up - it lit very quickly and easily - and gave me a blue flame with orange tips However, after just a few minutes, the flame pattern suddenly changes and then the stove extinguishes The tank is probably about half full of Coleman fuel and I haven't tried adjusting the gap between the coils. I know there are a lot of members here with these little stoves or their near-cousins - has anyone had this happen, or have any idea of what may be causing it? These stoves are so simple that apart from adjusting the coil gap there doesn't seem to be much else in the way of fettling or adjustment...any collective wisdom would be much appreciated!
THanks Presscall! Embarrassingly, I didn't think of that...but when I did prick it, the problem remained. It's as if the pressure at the jet is too high. When I tried it again I noticed two things: 1) when I heated the bottom of the coil with a lighter the fuel-air flow rate seemed to increase (i.e., larger flame), and 2) when the flame "candled" (produced a tall yellow narrow flame), the ignition point started slowly rising until it was a cm or so above the top coil and then seemed to extinguish when it got too high, although the fuel vapors were still coming out of the jet. The pictures above show the ignition point pretty far above the coil right before it goes out. The flame went out when the ignition point crept up too high. I'm wondering if the "combustion region" (I don't know the right term), i.e., the area where there is the fuel-air mixture being emitted from the jet is in the right concentration to support ignition combined with a high enough temperature to keep the flame going) is not working as designed. If that's the case, maybe the coil gap is too large - if the upper part of the coil is supposed to act like a flame spreader by creating a turbulent mixing region below it, but the gap is too large, then maybe the mixing region is above the coil instead of in the middle... Going now to see if I can measure the coil gap and maybe tighten it up a bit and see if that helps. I think the gap is supposed to be 0.045". If only I could find my feeler gauges...or better yet an old thin dime...my eyeball is not that well calibrated .
How good is your fuel? I have seen that with alcohol in gasoline stoves. Liftoff. Preheat longer.... this is just a guess, be careful with that. The flame rising, by itself, will put the flame out. It no longer heats the coil. Keep trying, maybe you can clear up the line. Maybe not???
Thanks! The fuel should be good. Now that I've burned through most of my older stored fuel, I'm now working with a can of Coleman fuel I bought at Walmart a few weeks ago. Although I could certainly be wrong, I don't think it's due to lack of preheating...nothing in the instructions talks about preheating, and it actually lights up and gets a good flame for a minute or two before it goes out. I actually "accidentally" preheated it on my last attempt...I was adjusting the amount of fuel in the tank and when I went to light it some residual spilled gas burned for about 2-5 sec on the tank. Some pretty impressive spurts of flame from the jet but it settled down pretty quickly. Since I can't find my feeler gauges, I used a modern dime (measured at 0.05" on some cheapo Harbor Freight calipers) and it would not fit the gap, so if the gap is too wide it's not *too too* wide. Lighting attempt number 3 also burned out after a few minutes, even with the windshield on and a kettle on top to keep everything warm. This is a puzzle. That being said, it's a fun puzzle...this could keep me occupied for the entire weekend . The design of this thing may be deceptively simple...it doesn't seem like it has enough moving parts to have much go wrong, but I suspect there is some complicated physics behind this little stove...time for some research...
Almost sounds like the wicking isn't soaking up the fuel fast enough. After it sits, it soaks it up, but once it burns a bit, it "dries" out, preventing it from staying lit. Just a hunch.
Interesting thought. Maybe I'll let it soak for a day while I watch YouTube coil stove videos and see if it gets more completely saturated ...
So, too much pressure. Used stoves have history, usually unknown. Maybe that is why it was for sale.????
have you pricked it again?? and again if needed? Not at all unusual for a stove to need repeated pricking when they haven't been run in a while. My Stesco works so well it's stunning, you just pass a flame by hole and it is off and running, so I have never had to troubleshoot anything BUT when I first got it I did have to prick it the first few times,
Kerophile, thanks so much for the Flame Theory 101 post...that is what makes this little puzzle so interesting. I've got enough stoves that it's not like I *need* to make another one work...but trying to figure it out why it's doing what it's doing will make it so much more satisfying when it does all work out. It does seem like it is slowly overpressurizing over time and blowing itself out. Just trying to figure out why. As far as history goes, it seems like it was very new - the windscreen hadn't even been taken out of the wrapping and the coils only had light discoloration. It seems to have far less history than the Phoebus 625 that I also recently acquired - that stove apparently has so much history it was all over my hands in the form of greasy soot by the time I got it out of the canister . The Stesco was pristine... I'm pricking it every time now. I think I'll start logging how long it takes to extinguish, and see if it slowly gets better with repeated attempts. It is a really cool little stove so I hope I can figure it out.
From what little we know (the stove has been barely used, the windscreen even less), I would guess this stove has had this behaviour from new. Never had a pot on it because it blows itself out first. I agree with @snwcmpr. If from new, the jet may be undersized? The other inputs into the jet pressure seem unlikely to be wrong, unless the position of the wicking makes a difference?
I agree that if it does have a problem, it's likely a manufacturing defect of some sort. The pricker goes easily into the jet (which on the Stesco seems to be simply a small hole drilled on the bottom coil loop) so the hole diameter is at least larger than the pricker wire. I just ran it again and filmed it from ignition until it died so that I could study the evolution of the flame pattern. I'll upload a link to the YouTube video, but a text summary is: Ignition at 0:15. Extinguished and repricked at 00:45, relit at 1:00 From 1:00 until about 3:00: - The flame front is about several mm below top coil - The max flame width about the same as the coil diameter - There is about a 50:50 split between blue/yellow flame height After about 3:00, the flame becomes narrower, taller, and more yellow. The flame from partially lifts off at around 3:44, seems to reach a maximum height at around 4:00-4:15, then reattaches at around 4:13. The flame gets narrower and the flame front completely detaches at 4:29, floats up then back down, and reattaches at around 4:36. It then gets steadily smaller until it goes out a little after five minutes. Although I hope that Majicwrench is right - that this may simply be some kind of burn-in phenomena and I'm just impatient - it's turning out to be interesting to just watch what's going on. If it had fired up the first time with no problems and boiled a pint of water, I'd probably have just repacked it and gone on to the next stove in need of repair. I guess that means I need another Stesco as a "control" stove for comparison. This is getting to be an expensive hobby
Link to YouTube video showing the Stesco flame evolution here: Stesco Flame Evolution - YouTube Let me know if that link doesn't work. If it does, pay no attention to the guy with the receding hairline between 00:45 and 1:00. I don't know who he is, but he shows up in my videos sometimes
The video link works. I was just thinking, the fuel cap doesn't need a fresh gasket, does it? May be losing pressure there.
Warrior, I don't think so. As far as I can tell, the fuel cap doesn't have a rubber gasket, just a lead seal that melts if the temperature gets too high and lets the stove depressurize through a hole in the cap. The NOS spare lead seal is still in the envelope. What's interesting is that I now wonder what the operating pressure profile is supposed to be like for these stoves. It actually seemed to give a stronger flame when cold and a weaker flame when hot, which is the opposite of what I would think would happen if the heat was supposed to pressurize the stove. Curiouser and curiouser...
Pretty sure there should be a fuel cap seal. My Little Injun Scout stove has a cork gasket. Doesn't show the gasket, but to show you it's the same type stove: Injun Scout
Well, if it is supposed to have a cork or rubber gasket over the lead seal in the fuel cap, as opposed to simply a soft lead seal, that would probably explain a lot . I have the cork plug that seals the jet for storage but it doesn't look like the fuel cap has anything else in it besides the lead blank.
Too much pressure, not a loss of pressure. Pricker fits... ? So not too small. If he makes it bigger, we cannot go back. I suspect a missing wick.
I noticed that when I prick it cold, fuel starts weeping out of the jet. I think that the pricker is breaking the capillary seal at the jet and letting fuel flow out, suggesting that there is something drawing up cold fuel from the tank to the jet, which I assume means the wick is working. Another test run after a cold pricking let enough fuel leak out that I got a mini-Roman candle effect as the liquid fuel was spitting out of the jet and getting caught up in the flame. It was sufficiently impressive that I think that I should probably wipe down the tank instead of trying to let the slight spilled fuel act as a priming flame...unfortunately, no pics of that spectacular little episode. I read all (I think) of the Stesco posts in the SRG and a number of posts suggested that they had difficulty getting these stoves to burn properly, but didn't give specifics so I can't tell if my problem is new or not. It may be that manufacturing quality was simply hit or miss. I'm not giving up though, that little stove is just pulling me in more and more. Thanks for all of the responses and suggestions so far, they have been very helpful! Remote diagnosis is challenging but it has been *really* useful to have all of the suggestions for new things to check out. I'm sure that if I find out what the issue is (if it's not just a burn-in issue) it will be so obvious in retrospect that I will be kicking myself.
