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Note the Ignition Air Duct or Channel. On my heater that was completely blocked. It almost seemed like a compound rather than just dirt. That might explain that my heater is in such good condition by having not operated since new. That air duct is critical to igniting the heater. In hindsight, I should have just cleared that duct, cleaned the burner "D" glow chamber with carburetor cleaner (as opposed to digging at the soot/carbon build-up with picking tools - screwing up the screen), and lastly run a fine wire into the fuel pipe with a carb cleaner flush. I'm convinced that would have restored my heater to operation. I base that on the fact that, except repairing the self-inflicted damage to my burner screen "wick", all that I did was to clean my heater fuel and air passages for the heater to work properly.
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A note for cleaning the Fuel Strainer type burner.
The back curved walls area of my integral fuel pipe Burner Burner 25 1922 10 00 00 "D" shaped glow pin chamber is a solid piece. Based upon visual inspection the brand new Fuel Strainer type Burner 25.2216.10.0000 aka stamped 25 2149 10 00 02 also has a solid back curved wall. I inspected the brand new Fuel Strainer glow plug chamber. Unfortunately I can't get a good picture inside so I'll describe it as best I can.
Refer to the 2nd burner picture in post #2 above for an idea of the screen and 3/16" hole position.
The Fuel Strainer burner is non-magnetic and appears to be stainless steel. The back curved walls area of the "D" glow pin chamber is solid. The flat wall has a screen embedded to it on the inside (in the glow pin chamber). An approximately 3/16" hole is in the flat wall out into an intermediate chamber. The screen surrounds that hole, but doesn't cover it. The screen disappears into a slot at the top of the "D" chamber flat wall. There are no other holes which I can see other than the tightly filled screen slot and 3/16" hole out to the intermediate chamber.
My cleaning suggestion applies to the Fuel Strainer burner the same as the integral fuel pipe style. It is best to rely on solvents like carburetor cleaner and avoid poking around too much. The screen attached to the wall may need cleaning, but you don't want to disturb it too much.
The two different fuel pipe entries leaves me a bit unsure as to actual primary ignition. I know that the screen/slot "wick" design is critical for both burner styles. It is interesting that the integral fuel pipe disappears behind the "D" chamber at the rear in contrast to the Fuel Strainer fuel pipe metering fuel into the "D" chamber from the front or glow plug end. I'm convinced that the glow plug produced flame ignites the fuel and exits thru the 3/16" hole into the intermediate chamber. The upstream air pressure via the Ignition Air Duct (Kanal) should overcome the larger downstream air opening (less pressure) so that the glow chamber flame moves out into the intermediate burner chamber. That same Ignition Air Duct air flow must also carry the fuel out to the glow plug chamber in any burner which has the Fuel Strainer. The heaters can be mounted in various orientations so the fuel isn't just gravity fed.
Anyway, things need to be clean and open enough, but not open too much, for flow. I know that the screen and slot, the Ignition Air Duct, fuel pipe, strainer, etc. needs to be clean enough for the heater to work.
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