This topic comes up with some regularity, so I decided to burn a couple of hours and write it up – I’ve used proper parts terminology, however recognizing these terms are not always clear to those new to GPAs, I’ve added clarifications in the initial use for some of the terms.
To some of you, none of this will be new. This is really aimed at beginners or someone that struggles with diagnosing issues. And apologies for the formatting; the bulleting is limited in the posts...
To more quickly diagnose issues with a given lantern, it's best to have an understanding of the systems that are incorporated in most lanterns. For this discussion we will assume it’s a single mantle lantern from Coleman’s “Golden years” such as the 200A or its predecessor the 242/3 series. These have the “Quick Light” feature, and that is important later in the diagnostics.
These diagnostics should convert generally to other models and even other makes. Having said that, some lanterns DO differ in some ways. Some of this can also carry over to radiant heaters, like the (rare) Coleman 519, or even stoves with some interpolation.
To Begin: Your lantern has three obvious features:
1. The fount (Tank) which stores the fuel
2. The globe/burner assembly where the mantle(s) live
3. The vent (top hat, lid…)
But these are not the systems. The systems are more numerous and complex.
Component Systems of a lantern: (Systems are Bolded)
1. The fount has three main features, two of which are systems:
1.1. The Fount housing which stores the fuel supply, and includes the fuel cap. It is a pressure vessel, if low pressure.
1.2. The Pump, pump tube and Check Valve (CV)
1.2.1. The Pump rod and pump Leather provides pressure. Some lanterns and other GPA’s may be somewhat self pressurizing as the heat of operation, if it gets to the fount or tank, will expand the air inside and add some to the pressure. Some GPA’s rely on this, some do not.
1.2.2. The CV is a one way ball check valve that keeps the air that got past it from coming right back out. On some (mostly older) GPA’s this may be a Non Return Valve (NRV) which is a spring loaded valve against a fuel resistant rubber seat.
1.2.3. The Pump Stem, which is a screw type needle valve to open or close access through the CV. (To prevent back leaking – the ball is a temporary seal and should not be relied on.)
1.3. The Fuel/Air (FA) tube, which feeds the Main control Valve assembly
1.3.1. The FA has two openings and is not a simple dip tube (It was in the very early lanterns and is still for some kerosene lanterns), it has the main fuel opening at the bottom, and an air bleed that, when the Main Control valve is open 1/4 turn, allows air to mix with the fuel so it’s easier to light when the lantern, and specifically the generator, is cold.
2. The Main Control Valve
2.1. The main control valve takes the fuel fed by its FA tube, and feeds that to the generator, which is screwed into the top of the Main control valve but is its own system.
2.1.1. Included in the main control valve is a control lever that runs the pricker rod inside the generator. Think of it as a tiny crank shaft that moves the pricker rod up and down.
2.2. The Generator:
2.2.1. The generator, “generates” vapor by converting the liquid fuel into its gaseous vaporized form. This is necessary, or the fuel would not burn evenly and light the mantle properly. This is visible during startup when you often see flames caused by the liquid fuel being burned and the burn is very “rich” (too much fuel for the oxygen)
126.96.36.199. The generator is parasitic to the heat of the mantles for its heat source. You can artificially preheat the generator and have an almost instant light up with no startup flame drama. It’s best to open the main valve long enough to hear the ‘gurgle” of fuel, then CLOSE THE VALVE. You will know when to reopen the main valve as that fuel in the generator will vaporize, and the mantle(s) will light but will need more fuel to stay lit…
188.8.131.52. The generator includes a tiny orifice that meters the fuel into the mixing chamber where it mixes with air introduced by the air tube (The air tube is often plugged in older long stored/disused lanterns by cobwebs, dead spiders and insects or even mud wasp nests.)
2.3. The mixing chamber and air feed tube:
2.3.1. As mentioned above, the generator orifice meters fuel here, and it’s mixed with air from the air feed tube to get the air/fuel mix needed for a clean burn.
2.4. The burner tube and burner ring: with screen (usually)
2.4.1. The burner tube and burner ring hangs from the mixing chamber, and the burner ring is where the mantle is tied on. The burner ring usually has a screen and the whole assembly stabilizes the air fuel mix before its ignited inside the mantle.
2.5. The Mantle:
2.5.1. The Mantle provides the “container” for the fuel to burn, and is treated so it glows with the heat of the burning fuel, thus producing the light.
2.6. The Globe and Vent:
2.6.1. These provide wind protection, and a path for the excess heat generated to be reasonably safely vented vertically. The surface heat can reach in excess of 700 degrees F, so care must be taken to avoid burns. You can light matches and even cigarettes off the hot gasses escaping… and you want to keep plastics away as they will melt and fuse…
2.7. The bail (handle) – Simple enough: a way to carry the lantern without burning yourself or holding it awkwardly – Don’t “store” the bail vertically while lit, as it can still get too hot to hold if it is up while lit very long. Something to think about as you take a lantern down from a hanger.
For an older lantern you want to ensure the basics are up to being lit:
• Does the pump produce pressure?
- If not, oil (neatsfoot oil is best) or replace the pump leather.If old and dry, oil it well; then you can “flatten” (Flair it out) it a bit if it is still not pumping or pumping well. This helps it close the gap in the tube. If all else fails, replace it. Newer lanterns may have neoprene pump “leathers” – these must be replaced if they don’t make pressure. You can replace the neoprene with real leather, but it may require the older type pump rod… I keep a supply of the common pump leathers in stock.
- Fuel caps have a gasket that commonly on older lanterns has dried out and cracked; this makes the cap leak which can be dangerous if it is a fast leak. I keep a supply of the commonly used cap gaskets in stock.
- Caps come 2 ways
- a three piece cap (Main cap, gasket insert, and insert retention screw)
- a one piece cap
- Replacing the cap gasket is simple in concept, but since it has been there for decades under pressure, and is often hard as a rock, can be tricky to get out. The tip o
f a sharply pointed knife, or a dentists pick can help, but most people, on the three piece caps, remove the insert, and use a torch to burn the gasket, and then it’s easy to scrape the remnants out.
- For one piece caps this is generally not an option if painted, plated or a modern aluminum replacement. Just work at it carefully (I prefer to clamp the cap in padded vise jaws to avoid me bleeding all over the work. You can also make a holder for the caps by boring a 1 and or 3/4” hole on a block of wood about the depth of the caps, then sawing it in half lengthwise. The same block can be bored with shallow holes for the inserts at 3/4” and 9/16”.)
• Does the fuel under pressure come out of the generator’s orifice? (Is the pricker rod down?)
These are the basics I’ll review generally if not a full dunk test. I’ll vary this, depending on the overall condition of the lantern as received, but even the cleanest lantern can have any of these issues!
Assuming you are past all the above pre-diagnostics, and have tried to light the lantern and are having issues, what are the symptoms?
No Fuel/No Burn/Intermittent Burn:
- Check the cap for leaks; Replace cap gasket as needed
- Dunk test for other leaks
The drawback is some water WILL get into the pump tube, so after you are done with the dunk test:
• remove the pump rod and most of the water will squeegee” out. (make sure to keep the screw needle valve CLOSED until the water is gone…)
• Pour a small amount of 90% isopropyl alcohol into the pump and shake a little and dump.
• Replace the pump rod – Now would be a good time to re-oil the pump leather.
Dunk Test Tip (thanks Cold Start!) cut a 1-1/2'' fingertip off a latex protective glove and place over the pump of a pressurized lantern. There is enough flex to allow you to crack open and reclose the pumps secondary air seal. You can do this pump leak test at anytime, before or after a restoration. Or as piece of mind on your favorite running lantern. If there is a pump leak the latex glove fills with air, and you get a "thumbs up" - In this case, it's not what you want to see. 15 minutes is sufficient for a final visual pass. And my addition what a great way to keep water OUT of the pump for the rest of the dunk test!
• Is the tank clean?
o Drain the tank – any particles? Of what?
If rust grit see below.
If just debris, rinse until clean.
o If rust particles:
BB dance (add Daisy steel bb’s (or equivalent) and water, and shake and drain repeatedly until you get NO debris at all. - You can also use a telescoping magnet to remove small flecks of loose rust in a fount if that is your only issue in there, and that can also help remove the BB's from the BB dance.
You may need to fill the tank with a rust eating solution:
• Citric Acid
• White vinegar
Keep after it till it rinses clean
Drain the water
Add some (maybe an ounce?) 90% Isopropyl alcohol – shake and dump
Blow out with air (you are trying to prevent flash rust)
CAREFULLY heat the tank (Hair dryer or heat gun; – place in the sun open on a hot day, on a hot car or truck hood) to get dry, OR
Add a small amount of camp fuel and shake and dump
Fill with camp fuel
• Remove the vent, globe and burner assembly exposing the tip of the generator:
o Make sure the pricker lever is down:
o Open the main valve 1/4 turn - Does the orifice have a fuel stream?
• flip the pricker lever 180 and re-verify (some have been known to be bent 180 out)
• Flip the pricker lever 360 several times, anything?
• Steady? - you have fuel
• Intermittent? sputtering -
o Open the valve more
• Does it get steady?
o Yes – you have fuel and the FA is working
Tilt the fount 90 degrees (Fount must be at least 1/2 full)
• Does it get steady?
o Yes – Pull the main valve and clean the FA tube assembly and clear the bottom orifice
o No - Pull the main valve and clean the FA tube assembly and clear the bottom orifice, AND the top orifice and the passages in between – you may need a new FA if really bad…
o Is the spring on the fuel control rod in the correct position? The spring goes on the underside of the fuel control rod collar (not on top) so that it pushes the fuel control rod up as the fuel control valve opens.
Inspect the mixing chamber for debris/mud…
• Last but not Least for fuel delivery - is the generator plugged?
o Generators can get plugged, particularly if used with other than Camp fuel (like pump gas), but they can often be resurrected:
o Remove the generator from the lantern, with the pricker rod if needed. (Sometimes they are stuck, sometimes they are staked…)
o Setup a place to safely hit the generator with a torch, and water for quenching
Use a Bernz-O-Matic type torch (propane or MaaP Gas) and heat to near red hot.
Use pliers (don’t crush the generator) and drop it in the water
Repeat and rinse
You will see flames come from the ends of the generator as the deposits inside burns out.
Eventually (if not staked in place), the pricker rod will come out if it was stuck. There may be a roll of screen near the tip of the pricker rod, just throw it away. If you try to keep it you will likely break the tiny pricker wire off in it.
Once all the “coke” has burned out, you can reassemble the generator and put it back on. It will likely be just fine.
Initial test burn:
You don’t actually need mantels tied on to do a test burn:
- Best to preheat the generator as it’s harder to do so without the mantle(s) on.
- Look for a small blue flame just on the mantle burner. (similar to a stoves Blue flame)
- You generally cannot open the valve fully – the excessive pressure can potentially blow the flame out.
- Leaving the main valve on while getting a match or lighter inside the globe. (Fuel vapor build up, and a mini explosion…)
- Too much initial tank pressure (try only 20 or 15 or even 10 pumps – remember, the fuller the tank, the higher the pressure you get for a given number of pumps)
- Missing burner screens (but not every lantern uses these, and light up without the screen can have more light up drama…)
- Remove the vent, globe and burner assembly.
- Make sure the air feed tube(s) and mixing chamber is clear of debris.
- Verify the generator AND orifice are the right one for the lantern (too large of an orifice, or a worn one, can cause over burn)
- Are the mantles the right size for the lantern?
- Is the orifice tight? (If loose it will drip excessive fuel...)
- Check for leaks - see fuel cap and dunk test above
- Remember, a full tank will drop pressure faster than one 1/2 full (VERY common on 222/226/229 backpack lanterns)
These are the typical major issues seen with a lantern. There are probably more “cures” that I would regard more as “tuning”:
- Don’t be afraid to try different mantles. Some may be better fit for a particular lantern (See “overburn”)
- Sometimes burning in mantles on initial light up instead of doing a pre-burn can make them shrink a bit more than with a pre-burn
- You can tie an oversized mantle higher on the burner ring
- Saving an unburned mantle or one that the string broke on:
- ALWAYS replace cracked/broken mantles! These can have a jet of flame that can burn through a generator (instant fireball) or damage or break the globe
- NEVER use half measures to repair a leaking Font – these ARE pressure vessels, and a leak can almost always mean a big fire.
o Same for stress cracks (certain brass founts are notorious for this)
Grinding/gritty feeling in the pump:
- Corroded Pump tube (should be visible) - use a brake cylinder hone to clean it up, and rinse the residue out WELL
- damaged/bent cup assembly - replace the cup (more common on the neoprene pumps)
- Bent Air Stem - its rubbing on the inside of the pump shaft. it doesn't take a lot for this to be and issue is it centered when seated? if not it should not be when open and pumping - Possible cause for this is worn out threads as well?
- Simple test for the bent Air Stem - remove it and try he pump. if the grinding goes away you know where it is.
Feel free in any comments to make suggestions for other issues and/or fixes