primus omnifuel

3:03 p.m. on July 25, 2010 (EDT)
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i just baught 'primus omnifuel' and i am

facing some difficulties with it.

i use petrol 95.

first, what is pre-heating and how long do

i have to do it before starting to cook?

second, the flame is cut of, not continueous

and yellow instead of blue. how can i fix it?

thanks in advance

7:16 p.m. on July 25, 2010 (EDT)
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What the H is petrol 95?

7:40 p.m. on July 25, 2010 (EDT)
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3,726 forum posts

It is regular unleaded gas if memory serves me correctly.

8:21 p.m. on July 25, 2010 (EDT)
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5,486 forum posts

The Primus Omni, like all liquid fuel stoves, has to be "primed". Second, you have to have the correct jet installed (the Omni comes with two jets, one for light fuels like white gas, butane, unleaded autogas, and others, the other for heavy fuels like kerosene, autodiesel, jet fuel, and some others - having the wrong jet in there can cause the yellow flame). Autogas actually should not be used, since it contains additives that eventually will corrode and/or leave deposits in the fuel line and jet, but is ok in an emergency.

The proper way to light a liquid fuel stove is as follows (these are not complete directions, but I expect you to use "common sense":

1. make sure you have the proper jet installed, the fuel bottle filled to the fill line with an approved fuel (list with the directions, fill line is about an inch below the mouth of the fuel bottle), the pump properly inserted in the fuel bottle, and the fuel line properly attached (connecting the stove and pump).

2. with the fuel valve closed, give the pump about 20 strokes (you will learn the proper amount by feel with experience). Inspect for fuel leaks.

3. If you are using a light liquid fuel (white gas, unleaded autogas, etc.), open the fuel valve a tiny crack (stove on a level surface, of course). As soon as you detect a small "spritz" of fuel, CLOSE THE VALVE! This will be enough fuel for priming (also called "preheating"). If you are using kerosene or other heavy fuel, you may need to use alcohol ("marine stove fuel") as a primer.

4. Light the primer fuel (peizo lighter, cigarette lighter, match), keeping you head away from the area of the burner. The flame will preheat the generator tube (the section of the fuel line that curves over the burner area). As it heats the tube, it will evaporate fuel in the fuel line providing pressure. You will soon hear the characteristic hiss of the fuel coming and into the burner, upon which the vapors will ignite and burn with a roar. As the flame burns down, slowly crack the fuel valve open. If you time this right, you will have a nice blue flame evenly around the burner plate of the burner. If you get a flare-up when cracking the valve open, just close it and wait a second or two, then slowly reopen the valve.

It takes a little practice to get it just right.

If you attach a butane canister (industry standard threaded canisters), you just open the valve and light the vapors coming out of the burner.

REMEMBER!!!! You are using highly flammable, potentially explosive fuels. Proceed with caution and care. The fastest way to learn properly is to seek the assistance of someone experienced with liquid fuel stoves to demonstrate the process and guide you through it.

11:32 p.m. on July 26, 2010 (EDT)
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318 forum posts

I got one of these for a song on craigslist. It was an amazing find almost new with the box, pump and instructions. Its been working like a dream on white gas.

12:01 a.m. on July 27, 2010 (EDT)
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5,486 forum posts

Ah, yes, the good old dependable Optimus suitcase stoves.

The lighting procedure for the Optimus, Primus, and Svea (Svea is now part of Optimus) is basically the same. Too bad the lighting is so poor in the YouTube video.

The Brit (that wasn't you, DrReaper, was it?) did as most Brits did with those stoves, used methylated spirits (aka "alcohol") to prime the stove. With white gas, you can use the white gas itself, no need for a separate priming fuel.

He did a great job of showing how it is not necessary to have a giant, leaping flame during priming. If your priming flame is more than 3 inches above the burner, you are overpriming. He could have let the priming flame burn down more - he actually opened the valve a little early, but did it a tiny bit at a time, which works just fine.

On his turning it off then back on and having it instantly relight, that only works if you turn the stove back on almost immediately, as he did. If you wait a few seconds longer than he did, you will need to use a match or lighter. Half a minute, and you have to redo the priming process, because the burner plate will be too cool.

One of these days, I need to make such a video for our high adventure training course.

4:50 p.m. on September 21, 2010 (EDT)
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I have a knock off of an 8R. I love vintage gear. I got this one for $20 at a nostalgia shop about 4 blocks from home.

5:31 a.m. on September 24, 2010 (EDT)
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2,312 forum posts

One more detail about starting that require priming:

Should the stove require re-priming or refilling the fuel tank MAKE SURE ALL FLAMES ARE OUT BEFORE REFILLING TANK OR PLACING FUEL IN THE SPIRIT CUP! The overwhelming majority of stove fire accidents occur while priming and refueling these stoves, with most of these accidents occurring because fuel or vapors found an unintended ignition source. And NEVER use liquid or gas canister stoves in a tent.

March 27, 2015
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