pulsating fuel line - primus omnifuel

12:04 a.m. on March 12, 2008 (EDT)
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I recently purchased a Primus Omnifuel stove.

After a few uses, I've noticed that it has started to release fuel in a pulsating manner (you can hear it pulsating throughout its operation). Is this normal? What causes this? I've tried pumping more air pressure into the fuel bottle, but it doesn't seem to rectify this behaviour.

1:15 a.m. on March 12, 2008 (EDT)
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1,902 forum posts

I tried to look at the manual, but didn't see one online. However, the design looks very similar to my Optimus Nova.

This problem could be due to several causes. Make sure you are using fresh fuel-white gas of some kind for starters. Old fuel could have some water condensation mixed with it. First, clean the jet using the jet cleaning tool that is built into the multi-tool. It may be that simple. If that doesn't solve the problem, next thing is to dismantle the fuel line and see if the stove has an inline filter. If so, pull the filter out and run the stove without it. If it is like my Nova, the filter is in the end of the fuel line where it attaches to the valve. If that works, then replace the filter.

My Nova acted up recently on a winter trip and once I removed the filter, it ran fine. I just left mine out. I suspect mine iced over, but who knows.

If these two fixes don't solve the problem, you may have to remove the jet as well and see if it is clogged. The manual should show you how to dismantle the stove.

12:41 p.m. on March 14, 2008 (EDT)
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Blizzy -
The Omnifuel, which is very similar to my Primus MFS, has a filter on the end of the fuel pickup tube on the pump. This sits inside the fuel bottle and is a white/clear tube with the filter being the white plastic "cap" on the end of the fuel pickup. Eventually this gets clogged, particularly if you have somehow gotten dirt into the fuel (guess what .. there is dirt out there in the wilderness!) Or, as Tom says, there is a tendency to get water condensing inside the fuel bottle and your can that you store the white gas (or kerosene) in. Since the Omni also accepts compressed gas canisters, do you also get the pulsing with the butane (it takes the industry standard threaded canister, whether from Primus, Snowpeak, MSR, Coleman, or others)? When putting the canister on, be sure to shake the liquid gas out of the fuel line, since for the first few minutes, you might get some flaring as drops of white gas are pushed on through the line by the butane. But this will soon clear.

The Omni differs from my MFS by having an additional simmer valve. Be sure you are using the combination of the two valves correctly. With the valve on the burner and the one on the pump (on the fuel bottle) fully closed, pump about 20 strokes. Then open the valve on the fuel bottle fully. Now you are ready to start the priming, lighting, and use of the stove. Crack the simmer valve (on the burner) slightly to get a tiny amount of fuel into the burner (no more than a quarter teaspoon; do not try to soak the whole burner!), then shut the simmer valve. Light the fuel in the burner (thus starting to heat the generator tube - that's the part of the fuel line that curves up by the burner). When the flame is nearly burned out, open the simmer valve, and your stove should light and burn without pulsing.

When you shut the stove off, the proper procedure is to open the simmer valve almost completely, then turn the fuel bottle over so that the "OFF" on the pump flange is up (this puts the pickup line into the air space in the fuel bottle and allows forcing all the liquid in the fuel line out through the burner). Let the stove burn down to the yellow flame, then blow out the flame. Do not close the valves until the hissing from the burner jet stops, indicating that all the liquid in the line is cleared out. At that point, close the valve on the fuel tank, then close the valve on the burner. This procedure will reduce the amount of cleaning you have to do over time (all stoves, liquid fuel or compressed gas, require cleaning of the fuel lines and burner jet to maintain their heat output and just plain work properly over time).

As Tom says, you may need to clean the fuel jet (you do have the correct jet installed, don't you? It should be the white gas one for white gas or compressed gas or the kerosene one for kerosene - using the wrong jet will cause pulsing as well). You also might need to clean the main fuel line (the old "pipe cleaner" trick).

12:07 a.m. on March 18, 2008 (EDT)
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5 forum posts

Thanks so much for the suggestions. I hope I don't have to clean it... I've only used it about five times.

Thanks so much for the pointers on how to properly operate this type of stove. You can only interpret so much through reading the technical instructions that come with the stove (eg. the number of times to pump the tank when full, turning the simmer valve to full before flipping the bottle to OFF).

I'll play around with the stove to see if I can get it to stop pulsating.

May 22, 2018
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