In over six years of collecting, including many earlier Air-O-Lanterns and Quick Lites, I have accumulated a small box of used loop generators (also called “pigtail” generators, Coleman part number Q99). These generators range in condition from like new and serviceable to partially or completely plugged to mangled beyond safe use.
Coleman made something like six million gasoline Quick Lite units, both lamps and lanterns, that featured the Q70 burner assembly using one of a few different generators, including the Q99. These generators take a two-match preheat, have permanently fixed packing, no integral tip cleaner, no moving parts in operation and were not designed to be serviced beyond an occasional prick of the threaded gas tip with a supplied tool, Coleman part number Q007. New old stock are still available, but these are getting more difficult to come by.
In spite of the disposable design of the generator, hobbyists have used a few methods to try and clear a plugged generator, including heating with a torch and quenching in water, the use of a “carbon cleaner” or other chemical sprayed into the packing to soak and dissolve carbon, and using air under pressure to release the old packing for renewal. I have tried all these methods alone and in combination. Results vary as expected.
I have, after some trial and error, worked out a renewal procedure that I believe gives a good result in terms of performance and longevity, but with the ability to easily clean and renew the packing at the end of the service cycle. It involves a complete rebuild of the generator—inspection, removing the old packing, thoroughly cleaning the inside of the generator tube and repacking with new medium.
The procedure outlined here may be modified to suit available tools and supplies, but as with any work done on gas pressure appliances, you do so at your own risk. Keep your wits about you while working and when finished with a rebuild, always light and “proof” a lantern outdoors. Keep a fire extinguisher ready. Also, I'm a Coleman guy exclusively, but a few other manufacturers used similar loop generators, including Sunshine Safety and AGM. I believe this procedure could be used for other similar generators, perhaps with some adaptation.
With the generator in hand, inspect it carefully. Is the generator close to the shape it should be with the tube intact with no kinks, bulges or splits, deep nicks or cracks? Does the gas tip thread in easily by hand and can it be snugged to assure the threads aren't stripped? Does the flared end have an even seat that is free of cracks? It's a judgment call, but for safety I'd reject a generator with obvious defects, and probably reject one that was marginal. You can salvage the tip for use on a different generator, and the attachment nut can be saved for use on a Q77. Is the steel attachment nut (square or hex) intact and not too corroded? It can be cleaned up with a light touch against a wire wheel on the bench grinder. Is there plenty of flare present on the attachment end, such that the nut is not in danger of falling off? The flare can be enhanced with a neat little flaring tool, once the flare has been annealed so it doesn't crack from being worked. Just heat the flare to dull red in the flame of a torch and let it cool or quench it in water.
Remove the tip and use a pricker wire or tool to make sure it passes through the orifice from the inside out. If the tip is really cruddy or packed with carbon, start it soaking in parts cleaner. I use a gallon can of Berryman B-12 Chemtool. Now might be a good time to make sure the tip is correct, marked 'Q' or 'V'.
For the Q99, I bought several feet each of steel cable in 1/16” and 3/32” diameter. This will be used to drill out the old packing from each end. The smaller 1/16” cable will fit through the threaded gas tip end of the generator while the 3/32” will fit in the flared end.
I used a Dremel with a diamond cutting wheel to cut different lengths of cable to be used for drilling. Whatever method you use to cut, it should be clean enough that the cable doesn't unravel.
You'll need a variable speed drill, preferably with a hand operated check, and if cordless, a strong battery and maybe even a fully-charged spare. Heavy rubber gloves are also recommended. Soak the generator in a shallow plastic tub with water, and plan to dip it frequently while you're working. The packing is asbestos and should be kept wetted. Chuck a short piece of cable and spin the drill in reverse to keep the cable from untwisting.
Withdraw the cable frequently and rinse the tufted packing off the cable end.
Use an appropriate length cable to keep the chuck close to the generator as you drill. This allows you to apply some force to advance the cable while drilling without bowing the cable outside the generator. You can also vary how far the cable is inserted in the chuck. It may be slow going at times, in which case you can switch the cable and start work from the other end of the generator.
The packing on most of these generators is asbestos bonded to a thin brass wire that is doubled over and inserted so it runs from close to the flared end to most of the way around the loop toward the tip end. The cable will chew away at and sometimes “ball up” this wire within the tube. Another trick to advance the cable is to switch the drill to forward and spin it slowly a turn or so. This will usually unravel the end of the cable a bit to grab at a tuft of the packing so it can be withdrawn.
A few tips as you work:
Apply the force needed to advance to cable, but not so much that the generator starts to bend out of shape. Don't be afraid to risk destroying a section of cable as you use it forward and reverse to get past a stubborn point in the generator tube. And don't fight with a piece of cable that isn't working for you, either because it has kinked or has unraveled enough to cause trouble inserting it in the tube—go cut a new section of cable or cut a fresh end on the cable. Be careful drilling from the gas tip end so that the spinning cable doesn't flatten the threads where the tip screws in. I suspect this would take a lot of force from the drill, but it's something to be aware of.
Once you have been able to drill in far enough from both ends to be sure that you have overlapped, work the cable in and out to allow the spinning cable to “scrub” the wall of the tube throughout. You may or may not be able to blow air through the generator at this point because of that balled up packing wire or other goop. That gets taken care of next.
Take a longer length (8”+) of clean 1/16” cable and try to work it all the way through the generator tube beginning at the threaded end. This is to push any remaining material out of the tube. Use flat-nosed pliers to grip the cable very close to the generator end if necessary and push the cable a little at a time. You may have to work at it going around the loop.
Hold it over the sink as it will push out anything remaining inside the tube, and the color is invariably black. If the cable won't pass all the way through and out the flared end, you have more drilling to do. Once the cable has cleared the tube, withdraw it and rinse everything well, then blow through the tube to see that it passes plenty of air.
Soak it overnight in Berryman or other parts cleaner along with the gas tip.
I invested in a small ultrasonic jewelry cleaner (about $40 on Amazon or eBay) and it has been invaluable for cleaning small parts. Retrieve the generator and tip from the Berryman, rinse well, work a pipe cleaner into both ends of the tube, then buzz the parts in hot water and a splash of Simple Green until you're confident the inside is clean, clean, clean.
Work until a pipe cleaner no longer pulls anything black from inside the tube. A little bronze or steel wool will spruce up the outside of the generator in a minute or two. However you choose to clean the generator and tip, please minimize your exposure to harsh chemicals with gloves or other protective gear.
When the cleaning work is done and the inside has dried, it's time to repack. Take about an 18” length of monofilament fishing leader (I used 12 lb test), fold it in half and pinch a mild crease in it, and work it all the way through the generator tube from the tip end so it exits the flared end. It should go quite easily. If not, there is still cleaning work to be done on the inside—more scrubbing with cable and another soak in parts cleaner.
I found online (both on eBay and Amazon) a product called silica wick that comes in various diameters down to 1 mm and various lengths up to 100 feet. It is evidently meant for use in rebuilding vaping devices, is braided, has strong capillary action and is heat resistant up to 1000 degrees C.
I got a short section to try in 3mm that performs well but is difficult to thread the length of the generator. I found a seller that offers it in 1.5mm and have been using that doubled over. I believe 2mm would also work well. A Q99 will use about 14 inches of it. With the monofilament loop sticking out the flared end, hook the wick through leaving about seven inches trailing as shown in the photo.
Pull the packing into the generator with the monofilament until the folded wick snugs up against the threaded boss for the gas tip, release one side and remove the fishing line, trim the packing flush with the flared end using sharp scissors and tuck the trimmed ends up in the tube a little. Blow through the generator to make sure it passes air, install the gas tip after repricking one last time and try blowing air through one last time onto the back of your hand. You should feel a light puff of air if it's passing properly. If not, work at clearing the tip until you can.
I have over 50 hours of running time on my first rebuild with only one reprick of the gas tip, a couple of hours in.