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DLE and others DRY Carbs?

Old 04-26-2015, 05:55 AM
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Bob Pastorello
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Default DLE and others DRY Carbs?

I've asked this years ago, I think, but my CRS is getting bad with my age....I have three or four gas-engine setup airframes, DLE 20, 30, 50, RCG 26, etc.

For a number of reasons, I have had them retired for a couple years, dry, empty tank, standing nose down in their places.
LAST time I did similar, I had to pull cowlings, carbs, re-wet the innards of the Walbro or DLE carbs, reassemble, and they ran like champs.
This spring, I'm wondering if someone has a magic method of getting gas INTO the carb innards, so the pump diaphragm and needle/seat will work like they're supposed to....without me needing to disassemble and manually wet all the parts.

Anyone have a magic trick? Like pressurizing the tank, choke on, full throttle till pulls gas? Or installing some kind of primer line into the carb itself? ANYONE???
Old 04-26-2015, 08:40 AM
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Truckracer
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I don't have any magic fixes other than leaving some fuel in the carb like you would with lawn equipment and chainsaws. I have heard of people injecting oil in the carb then turning the engine over with the choke on to pull it through the carb. I guess this prevents sticking of the flappers and needle but it seemed like that would make the first start up more difficult later on. If an engine sits around for a long time unused, I'd open the carb for inspection before use anyway so I never seem to have the problem. Likewise for tanks that have sat unused for a long period .... they always get an inspection and a new clunk line if needed.
Old 04-26-2015, 09:27 AM
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ahicks
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I haven't tried it (yet), but I read that the diaphragm that opens the fuel needle is sometimes accessible through a vent hole in the metal cover over it. If one were to push that diaphragm down (without penetrating it) using something stuck through that hole, you should then be able to fill the carb by pressurizing the fuel line - theoretically.
Old 04-26-2015, 10:29 AM
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Truckracer
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Originally Posted by ahicks View Post
I haven't tried it (yet), but I read that the diaphragm that opens the fuel needle is sometimes accessible through a vent hole in the metal cover over it. If one were to push that diaphragm down (without penetrating it) using something stuck through that hole, you should then be able to fill the carb by pressurizing the fuel line - theoretically.
That works if you don't have a vent line in place. But if you are that close to the cover and diaphragm, it is just as easy to remove the (4) screws and push it with your finger. You also accomplish an inspection during the process which is probably a good idea.
Old 04-26-2015, 01:31 PM
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Bob Pastorello
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Good discussion, guys, but my initial need is for a fix that doesn't make me remove the cowl, or do any disassembly. I've studied some stuff about adding primer bulbs, but not sure that the stock carbs on DLEs would permit adapting that fix. I wouldn't mind a third 'primer line', if that's what it takes, but I'm at a loss of where to attach it, or what to add to make it work.
Old 04-26-2015, 02:15 PM
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Originally Posted by Bob Pastorello View Post
Good discussion, guys, but my initial need is for a fix that doesn't make me remove the cowl, or do any disassembly. I've studied some stuff about adding primer bulbs, but not sure that the stock carbs on DLEs would permit adapting that fix. I wouldn't mind a third 'primer line', if that's what it takes, but I'm at a loss of where to attach it, or what to add to make it work.
I didn't know anything except the very basics of Walbro carbs, so I googled up a "how do they work". Here is one of the many links returned: http://helifreak.com/showthread.php?t=326599

I don't currently have any problems with my gas carbs, so I didn't read the entire explanation. I did keep it for the future. Maybe there is a clue in the article that lets you know how to open up the pump chamber and get fuel in when you have the problem you have. Good luck. I will be looking for your solution.

sincerely, Richard
Old 04-26-2015, 03:17 PM
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tande
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FWIW......if the inlet/needle can be forced off it's seat with one of those "Pop/Off" testers, can't we just fill it with fuel?.......
Old 04-26-2015, 03:38 PM
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Originally Posted by tande View Post
FWIW......if the inlet/needle can be forced off it's seat with one of those "Pop/Off" testers, can't we just fill it with fuel?.......
The pop off testers are not really designed for liquids. Another issue, while the needle can be opened as described by pushing on the regulator diaphragm, just opening that needle doesn't guarantee fuel will flow through the pump chamber. I have seen the pump flappers stuck to hard to the carb body where they were hard to open by physical means .... they had to be scraped off the body. In this case, no reasonable amount of fuel pressure from the tank or other external supplies would cause them to open without mechanical intervention. On another note, for those minor cases where the needle is just stuck .... what would be wrong with adding a vent line to the regulator cover ..... just like many of us already do to prevent the affects of cowl pressure on the carb operation. Even if it wasn't used for its more common purpose, simply pressurizing that line would force the needle off its seat and allow for unregulated fuel flow ..... perhaps from a pressurized gas tank. Just a thought.
Old 04-26-2015, 03:40 PM
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A "copy and paste" of post #38 in the Newbies Sticky:

Original:Av8tor1977

I've been contemplating lately how much help the use of a primer bulb on our planes could be, and how many problems it could solve, especially for newbies. I know, I don't really want one on my plane(s) either, but it does have some logic. When someone says "firing up your (weedeater, leaf blower, chainsaw)??" when you are using one on your plane, just tell them "Hey, at least my plane always runs!"

Here's the "argument". Most people don't have a clue about how a primer bulb system works, but it is pretty ingenious actually. It does not "push" fuel to the carb, and it does not "inject" fuel into the engine. What it does is draw fuel from the tank all the way into the regulator fuel chamber. It creates a suction that moves the regulator diaphragm open, which opens the inlet needle valve, which allows fuel to be drawn from the tank, through any filter you might have in the tank, through the inlet fuel tubing, through the fuel pump, through the inlet screen in the carb, past the regulator needle valve, and finally into the fuel chamber. The excess is then expelled through the other line in the primer bulb system, and dumped back into the tank.

So think of what all this accomplishes:

1. Flushes old fuel out of the carb and replaces it with fresh drawn from the tank.
2. Proves that the filter/clunk in your fuel tank is flowing.
3. Proves that there is probably no kink nor obstruction in your fuel feed line to the engine.
4. Proves that fuel can flow through the fuel pump, indicating that the check valves in the fuel pump are wet and probably functioning. (At least the inlet flapper valve is not stuck.)
5. Proves that the inlet screen in the carb itself can flow fuel.
6. Proves that the inlet needle is not stuck shut. (I have had this happen.)
7. Proves that the regulator diaphragm is not stuck in the closed position. (It still could be too stiff to operate correctly but at least it is opening the needle valve.)
8. Proves that there are probably not any air leaks at the fuel pump nor diaphragm cover gaskets.
9. Prevents the "dry carb won't draw fuel" syndrome.

Interesting heh?? I fix a lot of yard equipment, and the first thing I do after checking compression and spark is to put fresh fuel in and pump that primer bulb. If it doesn't pump fuel and fill up, the very first trouble shooting step is to find out why not.

AV8TOR

For those carbs that did not come with a primer port, one would need to be added. It should go into the fuel chamber below the carb diaphragm. A carefully drilled hole, with a piece of tubing pressed in and secured with Loctite would do the trick. Then just add a primer bulb, with the suction side going to your new primer port, and the outlet side of the primer bulb going to an entry into the fuel tank that would just dump the excess fuel from priming back into the tank. Stand alone primer bulbs can be found on e-bay or other sources; they are commonly used on chainsaws, and on some weed trimmers.

AV8TOR1977

Last edited by av8tor1977; 04-26-2015 at 03:48 PM.
Old 04-26-2015, 03:48 PM
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Bob Pastorello
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av8tor - I've read that post several times, and understand the logic. The flow "draw" makes perfect sense, and a "remote primer bulb" would meet my need to mount it somewhere accessible.
Could you provide more information about where you would suggest drilling these tap points on the carbs for the 20's or 30's ?? Maybe a pic of the location you recommend ("below the pump diaphragm") ??
Old 04-26-2015, 03:53 PM
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The main reason I have never considered a primer bulb on an airplane engine is because I have seen so many of them fail at the least convenient times on lawn equipment. One of those "it worked just fine last time but today it cracked and leaked" sort of things. I certainly agree it could have some merits though. It would have to be external to the carb though as in most cases the carb is buried in a cowl.
Old 04-26-2015, 03:56 PM
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Bob Pastorello
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TR- quite agree! I have seen them work, and fail, at almost similar usage rates. And the external to the carb, would be just the ticket for what I'm thinking.
Old 04-26-2015, 04:00 PM
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Originally Posted by Bob Pastorello View Post
av8tor - I've read that post several times, and understand the logic. The flow "draw" makes perfect sense, and a "remote primer bulb" would meet my need to mount it somewhere accessible.
Could you provide more information about where you would suggest drilling these tap points on the carbs for the 20's or 30's ?? Maybe a pic of the location you recommend ("below the pump diaphragm") ??
In any given carburetor, you would just have to have a good look at it, and locate where you could safely drill about a 1/8" hole where it would penetrate into the area below the regulator diaphragm. The hole needs to be able to pull a vacuum via the primer bulb on the fuel chamber below the diaphragm. Obviously, great care would have to be taken so that you don't drill into other carb passages, etc. Having a good look at a carb with a primer connection would be beneficial. Sorry, but I don't have any pictures to show what I mean at this time, but pulling a carb apart and looking closely at the fuel chamber below the regulator diaphragm will add some insight.

AV8TOR
Old 04-27-2015, 01:47 AM
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Lifer
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After a long period of storage I usually have the same problem. To solve the dry carb issue I direct prime the engine. A couple of my engines have the carb mounted on the cylinder so I set the throttle wide open and squirt fuel directly into the carb. If it has a rear-mounted carb I will invert the plane and inject some fuel in the exhaust pipe, turn the prop to bottom dead center and as I roll the plane in the upright position after assembly the fuel will slosh into the cylinder.
A difficult process but one that works. I usually only have to do the the first flight of the season after Winter storage.
Old 04-27-2015, 07:46 AM
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I have done two things to start engines with dry carbs. The first is to pull the spark plug and dribble fuel into the cylinder
and than start the engine on that prime, that will sometimes get it running and the stronger pulses from the running engine
gets the carb. working. Also putting in fuel into the exhaust pipe and turning the plane so some of it gets into the cylinder
( piston down) works too.

I have had this work more times than not, so you might give it a try.
Old 04-27-2015, 10:48 AM
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Bob Pastorello
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Thanks to av8tor and others, I've successfully modified spare carb #1 for DLE20. Have "remote primer bulbs" on the way, and some #2 nipples for an OS water cooled head ( they have shorter threaded portions, and relatively short barb area) to install onboard my 30cc Yak and Monolog 120 20cc powered planes. My bench testing shows the mod and addition work. I'll post pics and procedure on the 30cc when I do that one. This addition should solve forever the dry carb issue.
Old 04-27-2015, 11:20 AM
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I think that you will find that besides being able to pull fuel into a carb that has been out of use for a long time or run dry on purpose, that you will also experience somewhat faster/easier starts, cold or hot. The primer system is an ingenious design, and contrary to popular belief, you can not flood the engine no matter how many times you pump the primer. It is impossible to flood the engine using the primer unless there is a fault in the carb itself.

AV8TOR
Old 05-03-2015, 07:16 AM
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Bob Pastorello
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I have modified the stock carb on the DLE 30 by adding an access port/tubing to the fuel chamber under the pump diaphragm (near/adjacent to the main metering needle). Hooked up a "remote primer bulb", and it works. Two or three presses, NO choke, high idle, ONE flip cold starts. I think av8tor1977 and others' recommendations about this fix will work fine. Thanks, everyone.

I'll post pics, if anyone thinks it worthwhile.
Old 05-03-2015, 07:28 AM
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The old saying is "pics or it didn't happen"?

I think many need the pics to get the perspective of how to do it?
Old 05-03-2015, 09:23 AM
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I would like to see what it looks like as well. Always interested in something new.
Old 05-03-2015, 12:03 PM
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Bob Pastorello
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Here's my Primer Procedure

Step 1 - Remove the pump diaphragm plate (4 screws) with the pump diaphragm, and set aside. Inspect and replace anything needed.



Step 2 - This is the INSIDE of the fuel chamber, above the main metering needle. The hole you see is the inside end of a short piece of 3/32” brass tubing press-fit and secured with Loctite retaining compound (green), then a very small fillet of thin ca, kicked to cure. The black neoprene tubing going to the Primer Bulb attaches to this brass tubing on the outside of the carb. VERY CAREFUL examination is required to ensure NO interference with either the choke shaft/arm OR the throttle shaft/arm.
It is ABSOLUTELY necessary to drill the pilot hole with no larger a bit than 1/16th inch, and that you carefully drill from the outside of the carb body so as NOT to distort the inner bowl, nor damage the lift tang of the rocker for the metering needle. AFTER the pilot hole is drilled, you can drill the main hole for the brass tubing, but NOT all the way through the carb body housing.

Step 4 - Clean EVERYTHING as if it was going into space…”clean room” quality. Reinstall the pump plate. Install neoprene gas line from brass tubing to primer bulb and test. In practice, this primer bulb only requires a couple of half-presses to fill and empty/dry carb with fuel. On this DLE 30, after this mod, it doesn’t even require choking, and starts literally on first flip.
It was NEVER, EVER, like this, as it’s been installed in a long-legged Yak 55, and tank placement took LOTS of flips to draw any fuel.

This modification is NOT for someone inexperienced with these Walbro type pumper carbs, and certainly you need to be pretty skilled with pretty precision blind drilling, and the proper use of retaining and sealing compounds. If this gets messed up - the ONLY fix is a NEW carb!!!! Proceed with great caution.
Old 05-03-2015, 04:27 PM
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Originally Posted by av8tor1977 View Post
I think that you will find that besides being able to pull fuel into a carb that has been out of use for a long time or run dry on purpose, that you will also experience somewhat faster/easier starts, cold or hot. The primer system is an ingenious design, and contrary to popular belief, you can not flood the engine no matter how many times you pump the primer. It is impossible to flood the engine using the primer unless there is a fault in the carb itself.

AV8TOR
The primer is just a devise that purges the air out of the line to carb. If you watch how they work you will see the air trapped in the line as bubbles that return back to fuel tank. You will still need to choke the engine to help it start or prime the engine by giving a small shot of fuel in carb throat. If it starts & then quits, loosen the 4 screws and squirt some fuel in and around the diaphragm. Then re tighten the screws & try again. You can avoid all this....I will post how.
Old 05-03-2015, 05:04 PM
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Default Dried out carbs

To avoid that dried out carb is easy. The last run of the day, kill the engine by choking it from a Hi- Idle. This will pull extra fuel & oil to coat everything inside engine & carb will be wetter also. Now for you guys that think this is going to make a bad smell...just plug the exhaust with some paper towels. Leave choke closed. Now if you plane to not run the engine for a few months, make sure you use pure gas ( Purgas.com.) It leaves no varnish in the carb & will not harm rubber. Mix the Purgas with a good quality oil like Red Line to your ratio us normally use.

For you guys that do not believe this, try it in any of you 2 cycle yard equipment engines. You will find they will start a lot better. In fact if you was to start the engine several hours again after flooding it out...you will find quite often they will start with no choking at all. Don,t think it will not work...please TRY IT. I found this out over 20 years ago. My chainsaw never needed anything replaced in the carb, and my son-in-law runs it to this day. I only had to replace the pickup line in the tank that cracked. It is a good idea anyway because the pick-up filter should be replaced once in a few years. Now try this folks & let me know if I am right on. Thanks

Last edited by captinjohn; 05-03-2015 at 05:06 PM.
Old 05-04-2015, 06:14 AM
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Bob - Thanks for the excellent pics and detailed explaination. But what do you mean by "don't drill all the way through the carb housing"? Dont' you need to to get the opening to the pump area? (which is looks like you did) and to slide the tube into? Also, did you barb the outside end of that tube? Also, how \ where did you mount the primer bulb? It must be accessible, but I'm guessing you don't want it visible? And is there a T connecting it to the fuel line in the tank? Where do you get these bulbs? What's the brand?

The only reason I'm hesitant to try this is I don't have a dril press, though I do have a vice grip. Might experiment on an old carb. Thanks in advance.

Mike
Old 05-04-2015, 06:30 AM
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Bob Pastorello
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The smaller 1/16" hole goes all the way through. The larger drill diameter to accommodate the tubing is counterbore from outside. I also did one of these for practice after I knew where the hole needed to be for certain and went through the whole body thickness with the larger drill. Worked fine. Drill press not needed...I did this with my small cordless drill, regular old drill bits... No magic.
I also prefer function over form, so the primer bulb is externally mounted through the side of the cowl. It's a single tube type, and doesn't go anyplace. One fitting from the primer assy to the brass tubing I installed. I'll do a pic of this. No tees, no connection to fill or drain lines (or any lines to the tank).
I'll post pics later this morning. The primer bulb is quite a bit larger OD base than I was anticipating, so it's kind of an ugly as sin sort of thing. But, like I said, I always go function over form on these types of projects.
No drill press needed. Very soft aluminum, and very easily drilled.

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