Remove fuel from tank when done??? - RC Groups
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Aug 26, 2012, 11:17 AM
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Remove fuel from tank when done???

Hello all, First off I want to thank everyone on this forum, I have recieved alot of help and hope to share what I know when I can,,,DO NOT LAUGH TOO HARD at this question..
I have transitioned from electric to fuel planes,, I have a Brison Gasoline engine in my edge 540 and a MOKI 2.1 glo/Nitro engine in my Pitts
Here is my question
When I am done flying them,, should I pump the fuel back out of the tanks,,,On both the gas and nitro or only one,,, OR neither,,,
I bought these planes used and have put new tanks in, all new hoses, cleaned carbs, and replaced diaphragms,, I got them running good, I want to keep it that way,,,,
--I have heard arguements on both sides,, I am not sure what to do,, I have heard that leaving it in swells lines, and softens the diaphragm,,
--I have heard that removing it dries the diaphragm and lines out causing them to need replacement very often.
I know letting the fuel sit in them for a long time the fuel will break down and GEL up causing a total fuel system needing to be gone thru.
I have about 2 months of fuel aircraft experience,, I know that some of you have decades,, I am never to proud to ask and learn so I am asking,,, Thanks
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Aug 26, 2012, 12:17 PM
Registered User
Gas and glow fuel are different. With glow fuel, it's important to run the engine dry at the end of a flying session, because the glow fuel is alcohol based, which retains water which in turn rusts bearings and other steel components. The rust is bad for the bearings, but it is also bad for the rest of the engine, as rust particles floating about work like grinding compound in places you don't want. Emptying the tank is optional, but for me, emptying the tank is what I do before running the engine dry.

Gasoline does not have the water problems that glow has. It's best to leave the engine wet, just as you do with your chain saw, weed trimmer, leaf blower,etc, Gas has lubricity and the added oil adds more. Emptying the tank is optional, I empty mine if I don't know for sure that I will be flying again in the next day or so. Leaving fuel in it doesn't hurt anything. If you do leave fuel in it, it's a good idea to plug the vents to minimize fumes getting out.
Aug 26, 2012, 01:25 PM
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I support RCFVR.

No need to empty the fuel tank for gasoline operation since gasoline does not have affinity for water, water vapor or humidity any more than you empty your automoble fuel tank coming back home .

Gasoline operation fires the power stroke by a spark at the sparkplug. In fact some full size aircraft engines had power boost by water injection.

In the case of glow fuel operation the ignition is initiated by temperature created by the glow plug filament and compression. The firings keep the glow plug hot but the burning does not initiate till the temperature is hot enough due to the compression.

Due to the affinity of alcohol for water, dissolved water (humidity) in the alcohol affects the ignition temperature such that it may never reach an ignition with the compression designed in the glow engines.

It is then preferable to empty the fuel tank so that at the next flying session clean and water free fuel is available to the engine.

Enjoy good and reliable engine operation.

Aug 26, 2012, 02:05 PM
To some extent, the area where you live will govern what you do over a given period of time for each type of fuel.

Methanol is hydroscopic and will draw atmospheric water into it. So it is best to drain and tightly cap your supply at the end of a flying day no matter where you are. Some people say it is ok to leave your fuel in the tank overnight or a few days. But I advise against it. One of the products of combustion is water. And your pumping exhaust into your tank to pressurize the system.

Gasoline does age, go "sour", and gel over a period of time, so leaving it the tank for a day on two or a week or two should not be a problem. But if your live in the North and only fly 7-8 months a year, drain and dump your fuel supply and buy fresh in the spring.

Alcohol can affect the diaphrams in gas carbs. And automotive "gasoline" now contains up 15% ethanol. If your gas supply is such, drain the tank daily and run dry the engine. In our area. I know of at least one competitve IMAC flyer that will only use aviation gasoline in his engines.
Aug 26, 2012, 02:25 PM
CPA# 39
EscapeFlyer's Avatar
Methanol is hydroscopic and will draw atmospheric water into it. So it is best to drain and tightly cap your supply at the end of a flying day no matter where you are.
As an interesting side note on this...

I remember a club meeting in Denver at the MAS club, we would meet at Buz's hobby shop for meetings (Buz is the owner, manufacturer, and designer of Magnum Fuel.).

I remember Buz firing up an engine, and he preceded to pour 8oz of water into a fuel tank (Magnum Glow Fuel that is) while the engine was running. What blew us away was that the engine ran fine until the last ounce of water was poured in.

Granted, this would NOT be a good practice, but it shows how little hydroscopic effect has on fuel combustion. It would do ugly things to your engine if you let it sit for a period of time in terms of rust- so I still wouldn't use fuel that obviously has been seriously tainted by water, but am convinced leaving fuel in your tank overnight, or even several days for that matter, really just isn't that big of an issue.

(Bracing for the onslaught of fiery darts and arrows to be thrown at me....)

Aug 26, 2012, 02:29 PM
Registered User
I do use a Brison 2.4 myself, fantastic engines. You said you rebuilt the carb meaning you replaced the Diaphragm and you probably replaced it with the type that is alcohol proof. Because of the alcohol in the gas these days I got in the habit of draining my tank and running the carb dry but I have replaced mine too so it isn't really necessary to drain the tank and carb, just plug the breather. I still drain the tank.
I run YS glow engines so my tanks are a closed system, I can just remove the pressure from the tank and forget the fuel I have left. I can even pull the main line and pressure line and connect them together then run the engine dry, I have a friend that does it that way, I don't, I like to drain my tank.
You could do this with your Moki too. Moisture isn't going to get into a closed tank any more then it will in a closed can. Just connect the main line and pressure with a piece of copper tube and run the engine dry.
Thing is, draining your tanks is way too easy!! Running an engine dry is way too easy!! Why not just do it. Ever think what happens when a tank springs a leak??
I have had bungs come loose and lines decide to tear while the plane is in my shop. If I still had fuel in the tank it could get ugly, if it is a gas tank it will smell a bit too.
There are ways to do things and you don't need to drain any tank but it is just so easy to drain them, why not just do it?
Depending on where you live you can forget about dry running the engine too. Where I live the humidity is about 7% most of the year, except during the summer, it's our monsoon season right now so it is humid. Rust isn't a big problem for me but I still like to run them dry.
It's just a choice thing and I know a lot of people that don't drain there gassers, I do but only because it is easy, I really am very lazy!!!
Aug 26, 2012, 03:21 PM
Registered User
Crowfly's Avatar
I try to "defuel" mine. Both glow and gas. Not for the motors sake,but because I store my planes and helicopters in the basement. I sleep better without worrying about a fuel leak,and the water heater having a party. But I don't run them dry. I just get out the fuel my pump will remove.
Works for me.
Aug 26, 2012, 03:57 PM
AMA 537620
ChillPhatCat's Avatar
With my glow planes, I always pump my fuel tanks back into the jug when I'm done... there's no reason not to put it back since it's exposure to the atmosphere is limited in a single flying session. As long as you regularly run your engines and don't store the fuel too long between flights (like more than 6 months) I can't see it ever being a problem. I don't recall any fuel ever going bad as long as I cap the jug.

On my last flight of the day I pinch the feed line til the engine dies to get the fuel out of it.
Aug 26, 2012, 05:26 PM
Registered User
u2builder's Avatar
I never drain my glow fuel tanks. I don't really want to "contaminate" the fuel in the jug. I have about 20 glow planes hanging from the rafters. I leave whatever fuel is in them until I fly them again. Sometimes it is next year. Sometimes it might be two years for all I know. They all hang with whatever fuel is in them. I do not run the engines dry. Just shut them off. I live in the NE and we have our fair share of humid days in the summer, and the garage goes below freezing in the winter. I do put a liberal amount of 50 50 marvel tool oil/ATF in each plane at the end of the flying season and run Omega which has 30% castor oil. All my engines are Saitos. They all start right up whenever they are called upon to do so, even the next flying season. I usually clear the prop a few times before I fire them up, but not always. I think the Castor oil is probably what saves me. So far I have had good luck with bearings. Probably after I write this I will have problems. I am not saying it is the thing to do, only that it has seemed to work for me.
Aug 26, 2012, 05:46 PM
Registered User
The PIPE's Avatar

I DO have memories of the "ugly GREEN goop" in glow fuel tanks...

Dear Fellow RC-Goupers:

The PIPE Here...from my years in the RC hobby, I can easily remember the sights of brass-plumbed fuel tank stoppers having that "ugly GREEN goop" in them from leaving unused glow fuel in them a bit too's an outbreak of "verdigris", the usual manifestation of the same green patina (or just plain copper RUST) that appears on ANY copper-alloy public work of art, like the Statue of Liberty's actual copper sculptural cladding that give her the 3D shapes we all know about, or on the Gloucester, MA Gloucester Fisherman's Memorial. Brass and bronze can have it happen to them from their copper content in those alloys, and when one combines the hygroscopic (water-attracting) nature of methanol in our glow fuel with the usual soft brass 1/8" diameter fuel tank stopper feed-through lines...IF we leave some glow fuel in there a bit too long, presto, the green goop shows up !! Unplated brass clunk weights, or the "foamed-copper-look" clunks (to apparently help eliminate fuel foaming) can also have that happen to them, too...a plated clunk, or one from a non-copper-bearing alloy would be preferable to keep the "green goop" away as well.

I'm planning on going with STAINLESS STEEL tubing instead for future fuel line feed-throughs "through the stopper" for my return to the hobby in time...until then, I;'ve GOT to keep lookin' for a new JOB first...!

Yours Sincerely,

The PIPE....!!
Aug 26, 2012, 07:09 PM
Registered User
I always drain my glow fuel tanks and run the engine dry at the end of the flying day....Gasoline I don't.....But take a not store your gas tank full.....I plug the vent line to keep the smell in and the bad things out....I friend of mine borrowed some gas from me and with out telling me filled my tank to repay me...I plugged my vent line and stored the airplane in the garage....the heat expanding...and well the vapors split the tank at the I always check to make sure the tank is half empty or do not run a gas engine dry
Aug 26, 2012, 08:16 PM
Registered User
Mikecam's Avatar
All good advice. I'll only add I've started to defuel my gassers so as not to take off the next time out and have a flame out because I forgot to fill the tank. It does happen. With only the fuel in the lines and carb you won't get it started and warmed up plus make it out to the end of the runway before it runs out of fuel.
I also use viton in my tanks and it stays soft no matter, if running tygon keeping it wet with fuel will keep it soft.

With living in the north comes long term storage for small gas engines. About 7 years ago I stopped draining all my tanks ( caused issues with brittle gaskets) and instead use a fuel stabilizer and then drain the tank before use and top back up with fresh fuel. All my small gas engines have been fine since going to this storage philosophy. Seafoam works well for keeping a clean fuel system.
Aug 26, 2012, 09:10 PM
Registered User
THANKS for all the info fellas,, I have heard loud and clear,, Pump the glo fuel out of the tank and run the engine dry,,,, then put the plane up

As for the Gas, leave it in there,Just make sure it is not an absolute full tank, If its been in there a little while I will pump it out before flight and put fresh gas...
Aug 26, 2012, 09:28 PM
AMA 537620
ChillPhatCat's Avatar
I'll add this. The main reason I pump it out of my tank is that it has a bad habit of spilling out when I'm handling the plane, putting it in the car, taking it out, hanging it up for storage til the next time I take it out and of course doing minor repairs.
Aug 26, 2012, 10:32 PM
Registered User
earlwb's Avatar
I typically stop the gasoline engine after flying it and leave the fuel in the carb. When done for the day, I drain the fuel tank, and then plug the vent line. I leave the fuel in the carb too. Many people just leave the gasoline in the fuel tank and don't drain it too.It is like how we treat our trimmer engines, lawn mowers, cars, et cetera. I would suggest plugging the vent line so the gasoline doesn't evaporate too much before you go to use the plane again. So your choice, drain the fuel tank or leave the fuel in it. Either way is acceptable.

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