Primus Onmifuel maintenance - Part 2

4:24 p.m. on June 20, 2008 (EDT)
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This is in response to this thread here:

http://www.trailspace.com/forums/gear-repair/topics/43703.html

(Sorry, had to create a new thread since the original one has been closed for new posts. Please merge threads if possible.)

I couldn't fix the issue, so I returned the unit for an exchange of the same product to MEC. I know alot of you are pretty experienced with these stoves; could you offer some tips on how to keep it in good condition asides from the suggestions already made in the indicated thread above? I've done a search for this on the internet but just could not find much about it. So I figure I'd ask users of this site directly. You can only learn so much from reading manuals, and the majority of knowledge from real-life experience.

Some specific questions:

1. If you get snow/dirt/sand int the fuel line connector pipe (the long bendable fuel line, with the inset/needle at the end to connect to the bottle), what's the best way of cleaning it before attaching the line to the fuel bottle?

2. How many pumps is enough for a full fuel bottle? I don't want to pump it so much that it would damage the pumping mechanism.

3. In the event that there is something wrong with the stove, what's your standard procedure for troubleshooting/cleaning?

4. What are the most common problems? How do you avoid them/fix them when they happen?


I spoke to the person processing my exchange and he mentioned to always keep the fuel pump in the fuel bottle when transporting and storing your stove. Even if there is fuel inside. The pump is very sensitive to dirt, so keeping it in the bottle will reduce the risk of foreign particles getting into the fuel line.

4:26 p.m. on June 20, 2008 (EDT)
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Also, Bill S mentioned a "pipe cleaner" trick in the other thread. How do you go about doing this?

11:36 p.m. on June 23, 2008 (EDT)
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Quoting from Clyde Soles - treat all stoves as the barely contained explosive devices that they are.

Seriously - I have seen people get seriously hurt from exploding stoves and burned seriously by uncontrollable fires.

1. There is (or should be) a filter on the pickup end of the fuel pickup line attached to the pump (inside the fuel bottle). This should keep junk out of the fuel line. However, if you do not shut off the stove correctly, eventually, the non-volatile components of the fuel will build up a "lacquer" in the flexible part of the fuel line. Inside the fuel line, there is a braided wire cable. You can pull this cable out, using the little tool that came with the stove. Also remove the jet (you have to remove the "thimble" to get at the jet). Run some fuel into the fuel line and run the cable back and forth, using the fuel to flush out the gunk that is loosened (needless to say, do this in the outdoors, far far far away from any source of flame or spark). Use a wire brush to clean the cable itself. When it looks fairly clean, put the cable back in all the way. Connect to the fuel bottle. Pump 20-30 pumps, then open the valve to flush fuel through the line (no jet replaced yet). Please collect the fuel in a container to take to the hazardous waste facility nearest you (don't breathe the fumes, don't get near flame or sparks, don't get it on your skin - it is a petrochemical and can cause cancer, birth defects, etc - seriously). Clean the jet and replace it. Clean everything else on and around the burner. Button everything up the way you found it (or better, the way it is supposed to be). and you should have a good working stove.

Warning and disclaimer - I probably forgot to tell you something or one or more precautions, so I take no responsibility whatsoever if you should follow these directions and hurt, maim, injure, or kill yourself or anyone within 50 miles of you. Use common sense and take precautions, like having a fire extinguisher and someone competent in first aid nearby.

2. 20 pumps for a full bottle is recommended in the owner's pamphlet. You are unlikely to damage the pump when hand-pumping or to overpump. But beyond a certain point, the stove won't work as well if there is too much pressure. A partially empty fuel bottle takes more pumps. Watch the flame and learn to judge from the feel.

-- same disclaimer - do at your own risk.

3. If you do preventative maintenance every time you use the stove, you shouldn't have a problem. If you do have a problem, fix it.

4. Most common problem is operator neglect and operator error. Treat the stove as a flammable device about to ignite in a big ball of flame, maybe generating shrapnel. Treat it nice and gently. Keep it clean. Keep all seals and O-rings in good shape (not dried out and cracked). Don't stomp on it, don't cram it into your pack, don't drop it, don't stomp on it, don't try priming by dousing it in fuel (just a tiny spritz is more than enough, no 2 meter or taller flames).

6:29 p.m. on June 24, 2008 (EDT)
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Stoves are probably a bigger risk factor than lion, tigers and bears. Several years ago I had a leaking o-ring, due to neglect, it was completely my fault and reminded me to be more careful.
Getting burned when you are a long way from help is a bad, bad, situation. I personally never carry my fuel bottle with the pump in it, I always install the threaded plug that came with it. (Again, check your o-rings)
After I assemble my stove, and pump it up, I check for leaks by rubbing my finger under all the fittings/connections, then crack the valve to prime the cup and check again before lighting. It's just good practice, you cannot be too safe.

6:10 p.m. on June 25, 2008 (EDT)
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Hello.

Cannot add much regarding user servicing as I haven't had to maintain my stove yet (but I know I should do that sooner rather than later).

You are aware that the stove is de-pressurized while burning away the last of the meals needed fuel if you turn it over while it is working, don't you? You can just read the markings 'off' and 'on' on the black plastic top of the pump assembly.
For even safer use, try and use canisters if they are available.

Keeping the pump in the bottle, de-pressurized in the correct way, is the safest thing to do. Removing the pump every time and putting a fuel bottle top back on is just asking for trouble, especially if you have forgotten where the bottle top is and therefore have to put it back together or risk leaving it open and the pump exposed to dirt and the bottle open etc., while you hunt for the top.

A further safety tip: never look down on a working stove, especially if you are having problems lighting it. For some reason I still do it now and again.

Ok I just read the original thread, which looks good. As for the 'pulsing', I get it quite a lot and assumed it was over-pumping. I usually give it twice as many pump strokes as it says in the manual because, well, because I like to abuse my gear rather than believe what the manual says (doesn't everybody?). I will try it with some white gas next time and see what happens with the right amount of strokes but could be the jet needs cleaning on mine as well.

8:38 p.m. on June 25, 2008 (EDT)
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Jon.C You are correct about the pump, it does not hurt to leave it in the bottle and may be a help to less careful hikers in terms of keeping it clean.
I leave my pump in until I am ready to pack out, then I store it with my stove inside my cookware the way it came from MSR.
I keep my bottle top tethered to my bottle so it is always there. The pump is more susceptible to breakage/leakage than the bottle top and I just prefer to travel this way. I didn't start doing this until I saw what white gas does to stuff in a pack, this was caused by the valve not being tight enough. Just my personal preference.
I live southeast US, how about you?

4:16 a.m. on June 26, 2008 (EDT)
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I'm in the UK, TH, the english lake district. I have family who have hiked the Smokies, which is probably near you, and it looks beautiful.
Do MSR still use plastic for their pump handles? If so then that's a shame (I know of at least two breakages, one during the AT and he had to buy the whole assembly). Probably that is their only weak point as the wisperlight seemed pretty well made, if a little messy, when I used one about ten years ago.
On safety, for anyone reading, I would stay away from cheaper fuel bottles and use the OEM bottles for a second/bigger bottle. The materials have to resist all kinds of chemicals and we had a cheaper one storing petrol overnight (filled below max, cool environment) which just broke the top off.

All the best.

5:15 p.m. on June 26, 2008 (EDT)
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Jon.C
I bought my stove 12 years ago, yes it does have a plastic pump handle. I have not looked at a newer one, so I don't know if they have changed anything. The Smokies are a 5 hr. drive north for me, but that is where I play.
After I get my kids educated I hope to travel a little, UK is on my short list, it is good that we can talk.
Cheers

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