I have lived aboard for some 14 years including 7 New England winters with a Taylor 079 heater and an 030 cooker as shipmates. (Oh, yes and my wife Carolyn and various animals)The Primus burner is of course the heart of both appliances. It still amazes me that a mass produced device with only two moving parts can be so obstreperous.
Warning! What follows is an extremely boring description of Primus burner trouble shooting! Not for the faint of heart!
Of course their main down fall is dirty fuel. Since the advent of K1 kerosene things have improved a lot on this front. I used to clean burners in the 030 every month or two, now I get into them annually. I have two filters in the 030 lines: one glass bowl auto style filter and a sintered bronze filter I robbed out of a furnace nozzle. My stove requires restriction orifices to stop pulsing and these have fine mesh wire screening disks mounted before them. The orifices themselves I made from conventional ones but have mounted them about 3" upstream from the burners. This cuts down on their getting carboned up from the heat. If you want further details on this let me know otherwise I will leave it at that.
I assume that you know all about priming these burners and the need to regularly prick them. Attention to these two details usually cures most ills. The real problems come when older burners start to burn with yellow areas and pots start to get black on the bottom. Curing this sorts the men from the boys! The first urge is to go out an buy a rebuild kit (though sometimes it's a relatively new burner), install all the goodies and fire it up again. This is a good idea but frequently the flame still has yellow areas or burns better on one side. (This condition is basically caused by too much fuel or not enough air. Too little fuel and too much air causes a blue flame that is "detached" from the flame spreader.)
Part of the problem is that the rebuild kit components are frequently quite variable: nozzles have different size orifices, prickers are different lengths and sizes, stems have different tip angles etc. In addition they don't all work well together in different combinations! So we are forced to acquire a deeper understanding of these things.
The quality of the flame is influenced
by the amount of kerosene vapor and the amount of air. The former is determined
by the fuel pressure, the nipple orifice diameter and valve stem adjustment.
The latter is determined by the fuel pressure and the characteristics of the
"inner air ring" (the donut thing inside the flame spreader) and the flame spreader.
Kerosene flow issues:
First the pressure: I use the standard 15psi but sometimes a burner with a large orifice diameter will require a lower pressure (i.e.. less fuel) to burn blue.
Second the nipple orifice diameter: When new the nipples have a range of
orifice sizes. I hold them to the light and sort them according to big
and small. The big ones almost always let too much kero through and
yield a yellow or asymmetric flame. Smaller ones work best. Sometimes you can get the big ones to work with a spreader combination that gives a lot of air. See spreader notes to follow soon!
Third: valve stem. The stem actually plays a minor part in fuel adjustment. To adjust the pricker rack and stem I first turn the stem all the way in to the body of the burner. I then stick the pricker wire in the eraser end of a pencil which forms a handle of sorts. I then put the rack into the burner and, holding it down with slight pressure, turn out the stem. The rack will click on the stem "cog" five times. I then screw the stem in. You should feel it seat. After you install the nipple the stem should have almost 3/4 (5/8 maybe) of a turn from closed to pricker all the way up. After use the stem will develop a shoulder from contact with the valve seat. Often the burner will begin to turn itself lower during use because of this. You can try dressing it with a file while you spin it in a drill motor.
Incidentally, these burners like to run full open, if you want a lower flame try lowering the pressure. A "flame tamer" is useful for cooking.
Air issues: The biggie here is the flame spreader/inner donut combination. It took me a loooonnng time to finally realize that these two items are most of the solution to uneven, yellow burners and I still am a bit fuzzy on how it all works. The important thing seems to be the clearance between the flame spreader and donut: more seems to be better. When you find two that work well, KEEP THEM TOGETHER AS A SET! You can use them on other burners but keep them together.
I have noticed that the flame gets more air if you lift the spreader slightly. I tried filing little air passages around the base of the flame spreader. I also tried grinding slots around the base. Both ideas worked but were probably not worth the effort.
There seems to be interaction between the nozzle size/pressure and air flow so you have to experiment a bit and I don't always hit on the perfect combination of nipple and flame spreader/donut but I usually come close. One other problem is that I have amassed quite a collection of new nipples with holes that are too big. I buy parts separately instead of in kits. Nipples and prickers almost exclusively.
So, in summary, to get a clean even flame you need to have a nipple and flame spreader/donut combination that work well together. Since the problem is usually too much kero the nipple is usually the first thing to check.
I have found that genuine Optimus Primus burners work (worked (?): they were not being made last we heard) better and longer than the Patria burners. We used to buy them direct from Taylor in England. They test the burners they sell so you even get better Patria burners from them. I don't like Force 10 and I don't like their "diesel" Patria burners. They are just standard burners with different nozzles. They don't work with any diesel I've ever bought.
You can keep burners from pulsing with a fuel petcock in the line: turn petcock toward off til pulsing *just* stops. Open to clean. I do this on my heater.
My heater has an air tank made of
thick wall PVC pipe connected to the fuel tank via a low pressure air compressor
regulator. I pump up the air tank to 40 lbs or so and the regulator provides
7-15 psi to the fuel tank. This allows the heater to run without pumping or
attention for up to 12 hours. It also provides a way to regulate heat output
(by varying pressure) while running the burner full open. However, I NEVER leave
the heater unattended!!
I seal the burner base threads with red high temp silicone found in auto stores. I make spacer washers from gasket material to get valve stems to line up with holes in the appliance. I smear them with the red silicone to seal.
I hear you can use mineral spirits instead of kero. I have not confirmed this!
You can sometimes clean old nipples by heating them red hot with a propane torch. Be careful not to damage or distort the threads as they get soft when hot. I quench them in water after heating. If I could only come up with a way to repair prickers. Any suggestions?
Well, how much more of this can you take? I'll call it quits here. Our next boat will probably be propane since we intend to go to areas where kero is hard to find. I need to pass all this info on to somebody! Care to take up the torch?! (Or the burner!!) Don't you agree it's a fascinating hobby? :-) You should see my antique burner collection!! ;-)
Hope this is of some help, feel free to ask about specifics.
Ed Seling aboard "Moonshadow"