Pretiss Waber M1942 Stove Rebuild

I mentioned some weeks ago that I may have a new hobby. What began as a curiosity based on some old military stoves my father owned when I was a kid has turned into regular searches on ebay for trashed-out stoves and lanterns and many evenings tinkering with my purchases in the garage. But, if I’m not building boats at the moment this seems like an interesting thing to do.

The Prentiss Waber M-1942-MOD

The Prentiss Waber M-1942-MOD “Mountain” Stove

A month ago I purchased two Prentiss Waber M-1942-MOD(ified) “Mountain” Stoves. Both are dated, PW-1-45 (PW = Prestiss Waber). These stoves were made collectively, I believe, by Coleman, Prentiss Waber (a.k.a Preway) and Aladdin. When I received the first one, I was working on two other stoves, so I didn’t  take a close look at it, but by the time I received the second one, and compared the two, it was obvious that someone had tinkered with it before. So, I completely disassembled it. In my opinion, as long as you don’t break anything, this is a good way to learn about its’ operation and helps identify where things can go wrong. I’ve always enjoyed this. One time, back in my early twenties, I bought a two-cylinder, two-cycle, model airplane engine just so I could take it apart to see first-hand how the fuel delivery worked with only one carburetor, and no poppet valves, etc. That was pretty neat. Anyway, I disassembled the stove and got to work on cleaning it up.

Update for July 2017:

For some history about this stove, see my blog entry, The Mountain Stove

For a description of the features of this stove, see my blog entry,  Buying an M-1942 Stove

For a description of fettling this stove, see my blog entry, Minimal Effort to Blue Flame

This blog post updated 27 November 2016

For information about interchangeability of burner bowls, vaporizers and tip cleaners, please see my blog post on M1942 Vaporizers.

Identification (Added 27NOV16)

Sometimes I ask ebay sellers for the year or manufacturer of a stove they’re selling and they reply that there isn’t one on the stove. Though Aladdin’s stamping is generally lighter that the others, I haven’t see one yet that doesn’t have it. These are all on the windscreen/pot support.

m1942_id

Identifying an M1942-MOD, Aladdin, Prentiss Wabers, Coleman

Another identification feature is the fold-out feet. Each manufacturer made the feet slightly different. I bought a pair of stoves where someone swapped out the parts, but since the manufacturer is stamped in the windscreen/pot support and not in the frame I looked at lots of photos online to get the proper tank with the other parts.

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M-1942-MOD feet; Aladdin (l), Coleman (m), Prentiss Wabers (r)

Pumps

First, the pump. The pumps on these stoves are different than most other gas type stoves in that check valve (a.k.a. NRV) is built into the end to the removable pump tube, which also happens to be the same place you fill the tank with fuel. There are two styles of the NRV, which I didn’t know at the time. My first thought upon noticing this was that someone put in a homemade version of their own. But, I searched around the web and saw both styles on various forums. These little valves can be problematic if you don’t replace the rubber insert, as it dries out over time and allows fuel to back-up into the pump. Some people reported their stove catching fire because of this so I was certain to replace it right away. Another curious feature is that the pump itself is a storage tube for spare parts.

Addded 27NOV2016 – With more experience I know now that the two NRVs in the photo below are the M1942 style (upper) and the M1950 style (lower). I’ve been using both, so if you cannot find a suitable replacement spring for the M1942 type, you can substitute an M1950 spring/cup/gasket successfully. See my blog post on M1942 and M1950 NRV gaskets for more information.

The M1942 Pump. Note the Hollow Tube Can Hold Spare Parts

The M1942 Pump. Note the Hollow Tube Can Hold Spare Parts

The Two Styles of M-1942-MOD NRV

The Two Styles of M-1942-MOD NRV

I replaced the main On/Off valve graphite packing as it was also hard and they are relatively inexpensive and easy to replace, so why not change it now?

I reassembled the valve and installed it in the tank (see Assembly Note below before installation). Then I gave it a pressure check to see if fuel leaked anywhere and it did. I do this by installing the valve assembly without the burner bowl and pot support, pressurize the tank, press my finger over the vaporizer and then open the valve. It appears that the compression ring (the silver disk) was not mating properly to the brass valve body. I tightened it plenty, but it just wouldn’t seal. I spent a lot of time looking for solutions and because I have two stoves was able to swap parts. If appears to be the mating surface of the valve body itself. The valve bodies do not have replacement parts available so I can’t just swap this part out with a new one. Meanwhile, I found that a little Permatex #2 will seal it for now (Note: since this time, I’ve purchased additional stoves, swapped parts between them and both sealed without needing any sealer 19MAR2016).

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M-1942-MOD valve assembly fully disassembled

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Installing valve stem, with bushings and packing (see note before doing this)

Assembly Note: If you’ve removed the entire valve assembly, like I’ve done here, do not install the packing and valve stem/bushings before you install it in the stove. Here’s what to do: 1) install the valve stem/packing nut on the valve assembly and install the valve assembly using a deep-well socket and extension. The nut will help prevent damaging the threads and prevent bending the valve stem opening. I use Aviation Form-A-Gasket Sealant liquid (Item# 765-1210) on the tank threads as it was recommended by a Coleman repairman. Recall that proper clocking positions the valve stem opposite of the fuel fill opening. See photos later in this blog post if you’re not sure. And, remember to position the mounting post for the wrench on the pot-support/windscreen/frame above the main valve stem.When satisfied with the positioning, remove the nut. 2) place the small bushing on the valve stem with the beveled inside edge towards the wire which wraps around the valve stem. 3) install the packing, 4) install the large bushing, 5) insert into valve body, 6) thread the valve stem all the way closed, 6) install the valve stem/packing nut and tighten.

Installing the tip cleaner parts, assuming you removed them. Typically, I wouldn’t remove these, however this stove’s tip cleaner packing was gone (as in, missing!), so I needed to make one. Don’t remove it if it isn’t leaking. As far as I know, nobody has made them in 70 years! Well . . . except me, and I’ve made only a half-dozen and am still testing them.

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Drop in the tip-cleaner mount

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Install the tip-cleaner lever, packing and retainer-washer

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Note the direction of the retaining washer

Here is what the full assembly looks like, though you cannot install it in the stove this way. I’m only showing it this way for clarity.

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M-1942-MOD, Fully assembled valve assembly

The vaporizer/generator has a little screen which goes inside. These are almost always loaded with carbon and can be difficult to remove. I found a few places where I can get replacement screens and installed a new one. The tip cleaner needle goes through the middle of the screen so you need to be careful not to snag it when installing the vaporizer.

The Vaporizer with New Brass Screen Installed

The Vaporizer with New Brass Screen Installed

M-1942-MOD with Tip Cleaner Installed

M-1942-MOD with Tip Cleaner Installed

I finished re-assembling the stove and filled it with fuel, then gave it one more leak test. All good. I re-installed the burner bowl, pumped it up and opened the fuel valve long enough to fill the pre-heat cup. A side thought. I always thought that MSR invented the preheat cup as this is a common feature on the Whisperlite and other MSR stoves, but apparently it was invented during World War II or possibly earlier. It is present on this stove, some Coleman 520s, the American (AGM) M1941, and the M1950 stove (which was manufactured up into the 1980s, I believe). Anyway, I lit the pre-heat cup, watched it burn, checking for any flames where they don’t belong, and with everything going properly, opened the main valve and got a nice blue flame.

The M-1942-MOD with the Pre-heat Cup Lit

The M-1942-MOD with the Pre-heat Cup Lit

And Then . . . a Nice Blue Flame

And Then . . . a Nice Blue Flame

The second stove works without any maintenance other than a tank cleaning, new fuel cap gasket and new seal in the NRV valve. Now, I’ve got two working M-1942-MOD stoves and may just take one on a backpacking trip as these are very light little stoves. And, with that pre-heat cup, I’ll bet it lights-up nicely, high up, in the cool air of the mountains.

Location of instruction labels (added 27NOV2016) – It seems that the three manufacturers didn’t place the labels in the same place on the stove (see photo of stoves with original instruction labels).

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Label locations are different; Aladdin (l), Coleman (m) and Prentiss Wabers (r)

 

Update for 19MAR2016: If you have questions about assembly or what something looks like which I’ve omitted, please add a comment. I’ve rebuilt 6 of these stoves (four PWs, one Coleman C-A and one Aladdin) to date and have lots of photos.

Thanks for visiting my blog.

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15 comments on “Pretiss Waber M1942 Stove Rebuild

  1. Paul Lemieux says:

    Hi got a ?on m42 field stove, I got two myself and restored them both, but now I have gas going into the pump valve, is that supposed to be?

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    • sklcolorado says:

      Sorry for the late reply, I was out of town.

      No, definitely not. Did you also replace the check valve gasket (some people call this the pip)? You should never, or almost never, have fuel in there. It’ll vaporize and possibly ignite when the stove is operating. I had that problem on a stove as well. Might have been an M1950 but it is the same design. What you should do is pump the stove, and after 20 or 30 pumps, see if the pump tries to back out on its own due to tank pressure. It shouldn’t do this. Three things can be the problem if this happens, either the spring on the check valve is too weak, or else the gasket material is old and won’t seal. And, third, if it’s a new gasket and the spring is okay, the gasket isn’t sealing properly. Sometimes I think some of the replacement pip gaskets are too firm and don’t seat well against the pump tube. Let me know what you find out. – Steve

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  2. Hello. Do you have any photos of the valve stem assembly with the packing and related parts?

    Thankyou, Crechio

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    • sklcolorado says:

      I happen to have a stove completely disassembled so, I’ll go take a few photos and then post them. – Steve

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    • sklcolorado says:

      Hi Crechio, I updated this post to add more information and photo. Please let me know if it’s what you’re looking for. – Steve

      Like

  3. […] opted to bring one of the restored M1942 stoves , and it worked great the whole trip. He used it for one dinner, and two breakfasts, including […]

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  4. […] touchy. The flat, squared mating surface in the valves are reminiscent of the fittings on the M1942 stove’s vaporizer/ stainless steel disk. Those can be difficult to reinstall correctly as well because, you really need to get the the two […]

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  5. Bill Hood says:

    Nice looking stoves. I have a beater M1950 that works great and I’m hoping to find a 1942 at a flea market or garage sale.

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    • sklcolorado says:

      They really are. Except for the seals and knobs they’re stainless steel and brass, so they hold up really well. The last one I bought, I found in an antique mall for $18. It was still full of unleaded gasoline, the vaporizer was clogged and it needed new seals. After, cleaning it up, it’s the one I use regularly. Keep your eyes open and I’ll bet you find one.

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  6. Hello from Spain.
    Some weeks ago I bouht a M1942 Stove in Ebay. When arrived to my address I could see that the burner bowl It was very run down,and my question is , where I can find a new burner bowl?
    I asked in oldcolemanparts.com but they haven’t.

    Thaks in advance
    Sebastian

    Like

    • sklcolorado says:

      How bad is it? Send me a photo if possible. Since they are made of stainless steel and brass they are typically salvageable. I can think of two other solutions to your problem. The burner bowl used in the M1942 stove has three square holes in it so the pot support arms can pass through the burner bowl and fold up. After WWII, there were surplus items and/or old tooling available and on the M1950 stove, and only for Coleman, and only for the year 1951, surplus or old tooling burner bowls were used. I have two Coleman 1951, M1950 stoves and they both have the M1942 burner bowl. So, you could look around on ebay for a cheap stove just for the purpose of getting the correct burner bowl, then buy a standard round hole M1950 burner bowl from Old Coleman Parts and re-sell the 1951 M1950 stove. The second possibility is to buy the round hole M1950 burner bowl from Old Coleman Parts and cut the holes to the square shape to allow the pot support arms to fold away. Except for the square versus round holes, the two look the same. And the vaporizers used on M1950, M1942 and WWII 520 stoves are all the same so the threads will match. Let me know about the old one.

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  7. Jan Buchan says:

    Hi, I am trying to sort out a new vaporizer for an M1942 bought recently. Depending on where I look, forum sites disagree as to whether the Coleman 520 is compatible or not. As I can source a 520 but cannot find a M1942 version, can you just confirm that the former will fit? regards

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  8. […] Feel free to check out some of my other posts about old camp stoves by scrolling up to the top of the page and selecting the Stoves and Lanterns Topic, or specific posts about the M-1942 stove, like Vaporizers, Cold-weather Single-burner Stoves, and Prentiss Wabers M1942 Stove Rebuild. […]

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  9. […] or specific posts about the M-1942 stove, like Vaporizers, Cold-weather Single Burner Stoves, Prentiss Wabers M-1942 Stove Rebuild and The M-1942 Mountain […]

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