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MSR fuel pump leak in winter

10:22 p.m. on March 21, 2011 (EDT)
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352 forum posts

I have a quesiton for the MSR cracks out there : ever had fuel coming out of the valve assembly of the standard pump in winter? Mine leaked some fuel when nudged at -35C. Not a problem since white gas is hardly flammable at this temperature and it was fine above -30C. It's the stoves only "failure" so far. Not sure if it was not tight enough, the seal looks fine.

Keep in mind it gets a full tear down and clean up every year too. So : common thing or just needs some tightening? It's too warm now to test it again!

Thanks!

2:02 p.m. on March 22, 2011 (EDT)
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I have an Optimus Nova, which uses a metal pump assembly that is very similar to MSR.  Once, when using at around 15F, it began leaking slightly because the leather cup of the piston was a bit stiff, and thus not making a good seal.  Lubricating it a little, flaring the edges out slightly, and careful reassembly solved the problem. I haven't had any issues other than the once, and not since.

2:48 p.m. on March 22, 2011 (EDT)
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gonzan, was your pump leaking fuel, or just not pressurizing the fuel tank? If it were leaking fuel, the NRV(Non Return Valve: located at the bottom of the pump tube), was not functioning correctly.

3:05 p.m. on March 22, 2011 (EDT)
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Franc, until now, I hadn't heard of this occurring. It might be that at these temperatures the check valve(ball & spring) gets stuck(open). I'm not 100% confident in a plastic pump performing in extreme cold. Was it a newer model pump with a toggle valve, or an old wheel valve pump? Anyway, how about using a nice Optimus 111 with kero?

3:31 p.m. on March 22, 2011 (EDT)
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Here's a post from CCS(Classic Camp Stoves) which documents that even metal pumps are not immune to catastrophic failure. CCS Post

8:28 a.m. on March 23, 2011 (EDT)
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Check valve assembly was fine, good pressurisation. It was at the base of the valve (new type). I assumed the small black O ring had shrunk a bit because of the cold. It was fine if left untouched but leaked a bit when pressed sideways. I'll try it out some more next winter, but we only get about 5-6 days below -35c here.

I know a lot of people swear by the metal pumps, but I've never had a failure with the plastic msr. It's also better for your fingertips than cold metal!

10:13 a.m. on March 23, 2011 (EDT)
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It was several years ago, bt now that you mention it, I don't remember it leaking fuel, just not not presurizing the canister. 

9:08 p.m. on March 23, 2011 (EDT)
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At that temperature it could be a contraction of the rubber seals. It happens on telescopic poles.

8:23 a.m. on March 24, 2011 (EDT)
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I've had my MSR pump leak several times over the years and I can always tell because when I am hiking I smell gas.  On my very last trip (I just got back yesterday), I smelled gas and dumped the pack and pulled out the bottle---I usually always leave the pump attached to the fuel bottle---and found the on/off toggle to be slightly open, as if it opens on its own.  No matter how careful I am to tighten the off toggle down, it occasionally wants to open and leak gas.  Of course, I always relieve bottle pressure before packing up by unscrewing the pump from the bottle and retightening.

One solution is to completely remove the pump from the bottle when packing and replace it with a usual bottle stopper---then the challenge is to find a secure place for the exposed and fragile pump that doesn't get crushed with the normal backpacking stresses.  And of course it means carrying an extra bottle top.  Plus, the old bottle tops are MUCH preferred over the new fangled "kid proof" black and bulkier tops. 

For total security, I guess I'd remove the pump when packing and replace with a secure screw-in bottle cap.

 

3:37 p.m. on March 26, 2011 (EDT)
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Tipi: my pump is the opposite, if i shut down to tight it's hard to open.

My guess would also be the rubber seal due to the cold. I was concerned it could be a sign of a bigger problem but it's true that these pumps are very simple.

3:26 p.m. on April 7, 2011 (EDT)
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1,469 forum posts

sounds like shrinkage

April 16, 2014
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