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Gas Caps do seal out any condensation from entering the gas tank, despite the arguments here saying they do not

Dec 10, 2023#1

C

CraftsmanFlaws

The gas cap is believed by some that even when screwed on tight, still allows for condensation to enter.

There is an article on IFishFishing Forum, & I'll quote from it:

There isn't enough air volume within a tank to hold much vapor.
On average, tanks are half full, further reducing volume
The amount of water vapor in air is very small, even at 100% humidity
Conditions aren't right to cause condensation in a fuel tank.
_________________________________________________________________

This makes the most sense to me. how can condensation (moisture) penetrate through a tightened on gas cap?? Please, if you have some logical rebuttal to this, then post it.

Assuming, I'm wrong & IFishFishing author are wrong, the same posters who believe gas caps don't keep moisture out recommend to take a piece of plastic wrap & place it over where you will tighten the gas cap. However, at least in Craftsman mowers & I would think other mowers have the same design, it DOES NOT WORK because there is a string coming out the bottom of the gas cap, and at the other end of that string is a U-shaped large piece that hangs in the tank, & you have to turn it sideways to get it out of the tank. End result is you are holding a gas cap with a string. I don't understand its purpose other than it is a way of telling you, if the U-shaped piece is not completely submerged in gas, that you need to add fuel. This whole design is IMO ridiculous. Just have a gas cap without this extra nonsense of strings & U-shaped pieces. If the user can't use a flashlight to look in the tank & see the level, then they should hire a lawn service.

So, NO plastic wrap for me. A friend of mine suggested just placing the plastic wrap (or better a zip lock bag) over the hole & use rubber bands to keep it on and seal any outside condensation from entering. IMO, this is just too much of a hassle. If you want to take this to extremes, take a good size piece of plastic wrap. Place it over the entire tightened gas cap, & use an appropriately sized rubber band to seal it to the top of the gas tank's tube.

If you disagree, please post with something other than just stating that gas caps are not airtight & allow moisture through. You should read the article, "THE MYTH OF CONDENSATION IN FUEL TANKS"

The Myth of Condensation in Fuel Tanks

www.ifish.net

Dec 10, 2023#2

ILENGINE

So explain to me how my 4 different chainsaws with 3 different brands can have fuel added in the spring of the year from a sealed container with no water visible and then set on an elevated surface in a storage shed over the summer and come September-October when I get the saws out to use them the first thing I have to do is dump the gas and water out of the fuel tanks. Normally I will get 1/4 in of water in the bottom of a mayo jar from each saw, Were did the water come from.

Now to some more of your thoughts. First thing is the tether on the gas cap is just that. Regulations require that the fuel cap be attached to the tank for the same reason that the fuel cap on your vehicle is tethered to the tank. And lawnmower fuel caps have either not be vented or have charcoal ventilation since 2012 so therefore no chance of air exchange.

Prior to 2012 caps were vented and some were thread vented and would wick water up the threads after a rain or heavy dew, Some had visible vent holes in the top of the cap that would allow dew and/or rain to enter directly. Had a customer with a 5 hp OHV Briggs horizontal Intek that was stored under a tub out next to the garden would end up with half a tank of water after a heavy rain.

So the issue may not be condensation as you think but the water is coming from some place,

Dec 10, 2023#3

R

Rivets

That’s a 2007 thread posted in a fishing forum talking mainly about outboard engines. You just posted the part of the thread which backs your opinion. I’m not going to cut and paste the parts of that thread which says your wrong. Looks like you really want to get into a fight about who’s theory is right, I’m not going there. This thread should be locked before it gets out of hand, because these are theory and no scientific data is able to prove who’s right.

Dec 10, 2023#4

Hammermechanicman

Looks like another great internet debate. Just me, I store my zero turn completely full. Everthing else is empty and run dry. Never have a water problem. Probably a quarter of everything customers bring in have some water in the tank. I dump every handheld, push mower, tiller and snowblower that comes in. I see lots of water.

Dec 10, 2023#5

ILENGINE

Anybody else notice that all the briggs OHV push mower engines come in with water in the tank.

Dec 10, 2023#6

Scrubcadet10

Rivets said:
That’s a 2007 thread posted in a fishing forum talking mainly about outboard engines. You just posted the part of the thread which backs your opinion. I’m not going to cut and paste the parts of that thread which says your wrong. Looks like you really want to get into a fight about who’s theory is right, I’m not going there. This thread should be locked before it gets out of hand, because these are theory and no scientific data is able to prove who’s right.

Mr.Grinch at your service.

Dec 10, 2023#7

C

CraftsmanFlaws

Rivets said:
That’s a 2007 thread posted in a fishing forum talking mainly about outboard engines. You just posted the part of the thread which backs your opinion. I’m not going to cut and paste the parts of that thread which says your wrong. Looks like you really want to get into a fight about who’s theory is right, I’m not going there. This thread should be locked before it gets out of hand, because these are theory and no scientific data is able to prove who’s right.

If you're "not going to cut and paste the parts of that thread which says your wrong", then don't post this antagonistic post, which, looking at many of your other posts, it is clear that you consider your opinion as THE truth, when you don't do what you preach - where is your scientific data to prove that you are right? It is clear that you like to anger, annoy & offend other posters. You should be locked out, not my thread. This thread has hardly gotten out of hand; the other replies have either agreed or been civil.

Dec 11, 2023#8

Scrubcadet10

Rivets did not report your thread and none of your posts have been removed.

Dec 11, 2023#9

B

bertsmobile1

Water in fuel tanks come from 2 sources
1) bad fuel that had water in it to start with or from the storage container
2) humidity condensing from the air.

humidity from the air is called dew and is why the grass is sometimes wet in the morning

for the water to condense the temperature of the air above the fuel in the tank needs to drop below the dew point
AFAIK all mower fuel tanks are vented otherwise you end up with a vacuum lock in the fuel system
for fuel to get out of the tank air has to get in, simple physics
what most people miss is after the moisture condenses out of the air, it drops to the bottom of the fuel tank from where it has no means of escape.
further more hot humid air has a greater volume than cold air so as the air condenses over night it contracts allowing even more damp air into the tank.

And this process will repeat itself each & every night that there is a dew fall
collecting dew over night is a standard survival method taught to military & mariners.

Against this happening is the fact that most mowers have a plastic fuel tank and plastic is a thermal insulator so a lot of the time even if there is heavy dew on the grass the air in the fuel tank will never drop below due point .
With carbs it is different,
most of them are zinc so they conduct heat really well so not uncommon to find a few drops of water inside a carb but none in a tank.

As for the article , obviously written by some one who was traunt from school during science class as he seems to have forgotten that the sun goes down at night .

Dec 11, 2023#10

StarTech

Yes water can get in tank with fuel caps as they do vent inwards. And some do go bad too. Just had a tiller earlier that I put on a new carburetor with new fuel lines and new fuel. It came back a month later with water damage to the new carburetor. I found a bad fuel cap allowing rain water to enter via the vent hole.

And with ethanol fuels water vapor will combine with the fuel and then settle out as water. Small amounts at first until it builds up over time. Most is not noticeable as we are normally using our during the mowing season. It when they sit for extend periods that this settled out water seeks the lowest point which with gravity fed carbs is the carbs itself. Once there corrosion happens.

Besides most water get introduce from poorly sealed containers just like grass and other trash in fuel does. I rarely find in my eqiupment unless I get bad fuel from the local station which is why I quit them. There tanks has caps on them too but had a bad one that finally got replaced.

Dec 11, 2023#11

R

Rivets

Boy I hit a nerve. I just call them as I see them. I may not be right, but you also could be wrong. Let others who read this thread make their own decisions when they get both sides of this theory.

Dec 13, 2023#12

B

bertsmobile1

We had a fishing boat ( small one ) with an outboard and a sealed fuel tank so every now & then you had to pump it up

Dec 13, 2023#13

Hammermechanicman

bertsmobile1 said:
We had a fishing boat ( small one ) with an outboard and a sealed fuel tank so every now & then you had to pump it up

Sounds like one of the old 50's era Evinrude dual hose system that used air from the engine to pressurize the fuel tank. Haven't seen one of those for a few years.

Dec 14, 2023#14

B

bertsmobile1

It was 10th hand throw away
dad had an old pulling boat of the 12 oars x 2 men per oar
It was a very sturdy boat but a real hand full single handed
I got an old victa lawn mower outboard conversion in bad shape but the 125cc engine & 4" prop did not give much of a push.
don't know where the outboard came from all I remember was it was 2 strike, would either foul the plug or whisker the plug & the fuel tank was similar to a race car it was a stand alone can with some pipes & a bulb pump that was forever perishing

There is a good reason why I took up motorcycle riding.

Dec 16, 2023#15

Moparjoe499

CraftsmanFlaws said:
The gas cap is believed by some that even when screwed on tight, still allows for condensation to enter.

There is an article on IFishFishing Forum, & I'll quote from it:

There isn't enough air volume within a tank to hold much vapor.
On average, tanks are half full, further reducing volume
The amount of water vapor in air is very small, even at 100% humidity
Conditions aren't right to cause condensation in a fuel tank.
_________________________________________________________________

This makes the most sense to me. how can condensation (moisture) penetrate through a tightened on gas cap?? Please, if you have some logical rebuttal to this, then post it.

Assuming, I'm wrong & IFishFishing author are wrong, the same posters who believe gas caps don't keep moisture out recommend to take a piece of plastic wrap & place it over where you will tighten the gas cap. However, at least in Craftsman mowers & I would think other mowers have the same design, it DOES NOT WORK because there is a string coming out the bottom of the gas cap, and at the other end of that string is a U-shaped large piece that hangs in the tank, & you have to turn it sideways to get it out of the tank. End result is you are holding a gas cap with a string. I don't understand its purpose other than it is a way of telling you, if the U-shaped piece is not completely submerged in gas, that you need to add fuel. This whole design is IMO ridiculous. Just have a gas cap without this extra nonsense of strings & U-shaped pieces. If the user can't use a flashlight to look in the tank & see the level, then they should hire a lawn service.

So, NO plastic wrap for me. A friend of mine suggested just placing the plastic wrap (or better a zip lock bag) over the hole & use rubber bands to keep it on and seal any outside condensation from entering. IMO, this is just too much of a hassle. If you want to take this to extremes, take a good size piece of plastic wrap. Place it over the entire tightened gas cap, & use an appropriately sized rubber band to seal it to the top of the gas tank's tube.

If you disagree, please post with something other than just stating that gas caps are not airtight & allow moisture through. You should read the article, "THE MYTH OF CONDENSATION IN FUEL TANKS"

The Myth of Condensation in Fuel Tanks

www.ifish.net

If you use a mower often enough, there is no need to be concerned about condensation.

Dec 16, 2023#16

Moparjoe499

Hammermechanicman said:
Looks like another great internet debate. Just me, I store my zero turn completely full. Everthing else is empty and run dry. Never have a water problem. Probably a quarter of everything customers bring in have some water in the tank. I dump every handheld, push mower, tiller and snowblower that comes in. I see lots of water.

A couple weeks ago I started a snowblower that had been sitting in my garage for 6 years. I ran it for 5 minutes without any problems. People get all anal about the fuel worrying about if the cap has a good seal, draining the tanks dry, putting fuel stabilizer in the tanks, ect, ect. Unless you are purchasing 100% gasoline, then it already has 10% alcohol in it and the water will be burned when it is running.

Dec 16, 2023#17

Moparjoe499

StarTech said:
Yes water can get in tank with fuel caps as they do vent inwards. And some do go bad too. Just had a tiller earlier that I put on a new carburetor with new fuel lines and new fuel. It came back a month later with water damage to the new carburetor. I found a bad fuel cap allowing rain water to enter via the vent hole.

And with ethanol fuels water vapor will combine with the fuel and then settle out as water. Small amounts at first until it builds up over time. Most is not noticeable as we are normally using our during the mowing season. It when they sit for extend periods that this settled out water seeks the lowest point which with gravity fed carbs is the carbs itself. Once there corrosion happens.

Besides most water get introduce from poorly sealed containers just like grass and other trash in fuel does. I rarely find in my eqiupment unless I get bad fuel from the local station which is why I quit them. There tanks has caps on them too but had a bad one that finally got replaced.

I have never had a problem with water in the fuel. I have some methanol left over from drag racing. That should take care of any water.

Dec 16, 2023#18

C

Cajun power

CraftsmanFlaws said:
The gas cap is believed by some that even when screwed on tight, still allows for condensation to enter.

There is an article on IFishFishing Forum, & I'll quote from it:

There isn't enough air volume within a tank to hold much vapor.
On average, tanks are half full, further reducing volume
The amount of water vapor in air is very small, even at 100% humidity
Conditions aren't right to cause condensation in a fuel tank.
_________________________________________________________________

This makes the most sense to me. how can condensation (moisture) penetrate through a tightened on gas cap?? Please, if you have some logical rebuttal to this, then post it.

Assuming, I'm wrong & IFishFishing author are wrong, the same posters who believe gas caps don't keep moisture out recommend to take a piece of plastic wrap & place it over where you will tighten the gas cap. However, at least in Craftsman mowers & I would think other mowers have the same design, it DOES NOT WORK because there is a string coming out the bottom of the gas cap, and at the other end of that string is a U-shaped large piece that hangs in the tank, & you have to turn it sideways to get it out of the tank. End result is you are holding a gas cap with a string. I don't understand its purpose other than it is a way of telling you, if the U-shaped piece is not completely submerged in gas, that you need to add fuel. This whole design is IMO ridiculous. Just have a gas cap without this extra nonsense of strings & U-shaped pieces. If the user can't use a flashlight to look in the tank & see the level, then they should hire a lawn service.

So, NO plastic wrap for me. A friend of mine suggested just placing the plastic wrap (or better a zip lock bag) over the hole & use rubber bands to keep it on and seal any outside condensation from entering. IMO, this is just too much of a hassle. If you want to take this to extremes, take a good size piece of plastic wrap. Place it over the entire tightened gas cap, & use an appropriately sized rubber band to seal it to the top of the gas tank's tube.

If you disagree, please post with something other than just stating that gas caps are not airtight & allow moisture through. You should read the article, "THE MYTH OF CONDENSATION IN FUEL TANKS"

The Myth of Condensation in Fuel Tanks

www.ifish.net

the myth? lol....with years of proof that this is no myth you are going to expect anyone to accept that water ingress into fuel tanks is not a thing?

Lets start with some basics. gasoline is generally not water attracting..but the gasoline sold and used by almost all mower owners contains alcohol, which does attract water.

the cap bs and the volume bs. A rest, your assumption is that the volume is too small to make a difference and that the cap vent is either too small or that is provides some kind of one way valve protection against water vapor/condensation. So several things: 1) the tank vent is designed to release pressure build in the tank AND also to PREVENT negative pressure (vacuum), so it really is a two way valve. It's designed to be an "OPEN SYSTEM" operating to prevent fuel vapor from building up dangerous high pressure in the tank and also preventings a negative pressure a vacuum in the tank as the engine is operating. Whether this is a gravity fed fuel engine or a pump fed fuel engine, the design is the same. It's a two way valve. And this also occurs IN STORAGE. Because you see, the temperature ambient is also going to cause fuel vapors to expand and contract. And thus even in storage, this valve is constantly moving from open to close, close to open..ever so slightly, but over time, yes, this is going to allow water vapor from the atmosphere (AND CONDENSATION THAT FORMS RIGHT AT THE EDGES OF THAT VENT) to be entrapped and to enter the tank. Water vapor is heavier than fuel, and heavier than fuel vapor..so you have a density issue and this results in fuel vapor going to the bottom of the tank, below fuel. In this area, it accumulates because it cannot escape the lighter density of fuel vapor and fuel liquid on top. Over TIME, this also happens with fuel cans that you use to fill your fuel at the pump. When you open the cap on your portable fuel tank, you are allowing the inrush of fuel from the pump into a quite large opening..it is during this moment when you actually have a very interesting water vapor introduction into the fuel and into the fuel can. Also, one must understand that even at fuel stations, there is a certain amount of water contamination as well. Especially for gasoline sold as alcohol mix. For most vehicles, this small amount of water/water vapor is not really a problem, because auto engines are actually engineered and designed to operate with small amounts of water contamination and still be reliable. However for small engines, air cooled, small amounts of water/water vapor has a much greater impact over time.
Here is an easy experiment you can prove for yourself.

fill your mower tank half full with gas. let it sit for 3 months over the winter. At 3 months, drain the tank completely in a glass mason jar. Notice the fuel-water separation. That is just reality.

now the argument about how much damage can happen with water in fuel? that's a separate question, but important nonetheless. Over time, especially with long storage fuel, water becomes a problem associated with rust and corrosion and also tends to cause fuel lines to become brittle or to collapse internally. Some fuel filters also have different metal components and water creates dissimilar metal corrosion internally, just as it will do with carbs...it's the water that becomes the ion transport, not the fuel...almost all carb contamination from corrosion is caused by water/water vapor. what can you do about it? again, another separate question. It's actually a good practice to NOT STORE Fuel in a tank or a carb for long periods. I do this by emptying the tank and running the engine until it starves from fuel and then I open the carb and allow it to dry, and open the fuel lines too. I smoke the head cylinder with a little motor oil, and then put it all back together. When it comes out of storage, the tank is filled with fresh fuel, and I drain about a 1/2 pint of it out of the fuel line right before the carb...into a glass mason jar. I look for contamination and water vapor. because you see EVEN IN AN EMPTY FUEL TANK< WATER VAPOR CAN HAPPEN. it's a combination of hot/cold weather and that tank vent which is a two way valve...water Can and does accumulate there even when it's empty. This is particularly true for the deep south where high humidity is a year wide environmental reality.

Dec 16, 2023#19

G

Gord Baker

CraftsmanFlaws said:
The gas cap is believed by some that even when screwed on tight, still allows for condensation to enter.

There is an article on IFishFishing Forum, & I'll quote from it:

There isn't enough air volume within a tank to hold much vapor.
On average, tanks are half full, further reducing volume
The amount of water vapor in air is very small, even at 100% humidity
Conditions aren't right to cause condensation in a fuel tank.
_________________________________________________________________

This makes the most sense to me. how can condensation (moisture) penetrate through a tightened on gas cap?? Please, if you have some logical rebuttal to this, then post it.

Assuming, I'm wrong & IFishFishing author are wrong, the same posters who believe gas caps don't keep moisture out recommend to take a piece of plastic wrap & place it over where you will tighten the gas cap. However, at least in Craftsman mowers & I would think other mowers have the same design, it DOES NOT WORK because there is a string coming out the bottom of the gas cap, and at the other end of that string is a U-shaped large piece that hangs in the tank, & you have to turn it sideways to get it out of the tank. End result is you are holding a gas cap with a string. I don't understand its purpose other than it is a way of telling you, if the U-shaped piece is not completely submerged in gas, that you need to add fuel. This whole design is IMO ridiculous. Just have a gas cap without this extra nonsense of strings & U-shaped pieces. If the user can't use a flashlight to look in the tank & see the level, then they should hire a lawn service.

So, NO plastic wrap for me. A friend of mine suggested just placing the plastic wrap (or better a zip lock bag) over the hole & use rubber bands to keep it on and seal any outside condensation from entering. IMO, this is just too much of a hassle. If you want to take this to extremes, take a good size piece of plastic wrap. Place it over the entire tightened gas cap, & use an appropriately sized rubber band to seal it to the top of the gas tank's tube.

If you disagree, please post with something other than just stating that gas caps are not airtight & allow moisture through. You should read the article, "THE MYTH OF CONDENSATION IN FUEL TANKS"

The Myth of Condensation in Fuel Tanks

www.ifish.net

Air contains Moisture. A Fuel Tank MUST be vented to allow fuel to flow out, thus fresh air is being constantly drawn into the tank. Covering the fill neck with plastic will help with that if it is a tank not being used for an engine. To store Fuel, fill the tank to the Top and keep in a cool dry place. Try to use it within 30 days and refresh tank. Ethanol absorbs Moisture. That is the big problem.

Dec 16, 2023#20

G

Gord Baker

Moparjoe499 said:
I have never had a problem with water in the fuel. I have some methanol left over from drag racing. That should take care of any water.

Be careful with the Methanol. It can seize plastic shutoff valves etc.

Dec 16, 2023#21

Cusser

Gord Baker said:
Air contains Moisture. A Fuel Tank MUST be vented to allow fuel to flow out, thus fresh air is being constantly drawn into the tank.

THIS !!!!

This information is from a "well-known" cussing chemist !!!

Dec 16, 2023#22

T

Tornadoman

CraftsmanFlaws said:
The gas cap is believed by some that even when screwed on tight, still allows for condensation to enter.

There is an article on IFishFishing Forum, & I'll quote from it:

There isn't enough air volume within a tank to hold much vapor.
On average, tanks are half full, further reducing volume
The amount of water vapor in air is very small, even at 100% humidity
Conditions aren't right to cause condensation in a fuel tank.
_________________________________________________________________

This makes the most sense to me. how can condensation (moisture) penetrate through a tightened on gas cap?? Please, if you have some logical rebuttal to this, then post it.

Assuming, I'm wrong & IFishFishing author are wrong, the same posters who believe gas caps don't keep moisture out recommend to take a piece of plastic wrap & place it over where you will tighten the gas cap. However, at least in Craftsman mowers & I would think other mowers have the same design, it DOES NOT WORK because there is a string coming out the bottom of the gas cap, and at the other end of that string is a U-shaped large piece that hangs in the tank, & you have to turn it sideways to get it out of the tank. End result is you are holding a gas cap with a string. I don't understand its purpose other than it is a way of telling you, if the U-shaped piece is not completely submerged in gas, that you need to add fuel. This whole design is IMO ridiculous. Just have a gas cap without this extra nonsense of strings & U-shaped pieces. If the user can't use a flashlight to look in the tank & see the level, then they should hire a lawn service.

So, NO plastic wrap for me. A friend of mine suggested just placing the plastic wrap (or better a zip lock bag) over the hole & use rubber bands to keep it on and seal any outside condensation from entering. IMO, this is just too much of a hassle. If you want to take this to extremes, take a good size piece of plastic wrap. Place it over the entire tightened gas cap, & use an appropriately sized rubber band to seal it to the top of the gas tank's tube.

If you disagree, please post with something other than just stating that gas caps are not airtight & allow moisture through. You should read the article, "THE MYTH OF CONDENSATION IN FUEL TANKS"

The Myth of Condensation in Fuel Tanks

www.ifish.net

A plastic gas tank will usually have very little if any condensation. A metal tank is a whole other story. Lots of condensation. That is why most, if not all manufacturers of anything use plastic tanks.

Dec 16, 2023#23

G

Gord Baker

Hmmmmmmmmmm. Possibly.

Dec 16, 2023#24

ILENGINE

Tornadoman said:
A plastic gas tank will usually have very little if any condensation. A metal tank is a whole other story. Lots of condensation. That is why most, if not all manufacturers of anything use plastic tanks.

Because that is due to most plastic gas cans contain non vented filler necks with no other venting system. Hence the expanding and contracting of the side when the temps change. Metal with the same non venting design don't have water condensation issue either.

Dec 16, 2023#25

S

Shady oak

Isn’t condensation caused by the difference in temps between inside the tank, and outside, with a little bit of humidity thrown in? Condensation doesn’t leak in through a gas cap. Asking for a friend!

Dec 16, 2023#26

ChiefH

ILENGINE said:
So explain to me how my 4 different chainsaws with 3 different brands can have fuel added in the spring of the year from a sealed container with no water visible and then set on an elevated surface in a storage shed over the summer and come September-October when I get the saws out to use them the first thing I have to do is dump the gas and water out of the fuel tanks. Normally I will get 1/4 in of water in the bottom of a mayo jar from each saw, Were did the water come from.

Now to some more of your thoughts. First thing is the tether on the gas cap is just that. Regulations require that the fuel cap be attached to the tank for the same reason that the fuel cap on your vehicle is tethered to the tank. And lawnmower fuel caps have either not be vented or have charcoal ventilation since 2012 so therefore no chance of air exchange.

Prior to 2012 caps were vented and some were thread vented and would wick water up the threads after a rain or heavy dew, Some had visible vent holes in the top of the cap that would allow dew and/or rain to enter directly. Had a customer with a 5 hp OHV Briggs horizontal Intek that was stored under a tub out next to the garden would end up with half a tank of water after a heavy rain.

So the issue may not be condensation as you think but the water is coming from some place,

I do not know why you get so much water in your gas chain saw tanks. I have one chain saw, one backpack blower, one hand held blower, one line trimmer, two walk behind lawn mowers, one shredder-chipper, one snow thrower, and I do not get water in any of the tanks. I DO however, refill the tank after use so that the tank has little room for air (ever air with moisture). I use Sta-Bil in all of my straight gas containers, and 2-cycle oil in my mix gas containers. I do not seem to get moisture in my storage containers. I live in a summer time humid area (Shenandoah Valley, Va.)

Dec 16, 2023#27

F

farmerdave1954

CraftsmanFlaws said:
The gas cap is believed by some that even when screwed on tight, still allows for condensation to enter.

There is an article on IFishFishing Forum, & I'll quote from it:

There isn't enough air volume within a tank to hold much vapor.
On average, tanks are half full, further reducing volume
The amount of water vapor in air is very small, even at 100% humidity
Conditions aren't right to cause condensation in a fuel tank.
_________________________________________________________________

This makes the most sense to me. how can condensation (moisture) penetrate through a tightened on gas cap?? Please, if you have some logical rebuttal to this, then post it.

Assuming, I'm wrong & IFishFishing author are wrong, the same posters who believe gas caps don't keep moisture out recommend to take a piece of plastic wrap & place it over where you will tighten the gas cap. However, at least in Craftsman mowers & I would think other mowers have the same design, it DOES NOT WORK because there is a string coming out the bottom of the gas cap, and at the other end of that string is a U-shaped large piece that hangs in the tank, & you have to turn it sideways to get it out of the tank. End result is you are holding a gas cap with a string. I don't understand its purpose other than it is a way of telling you, if the U-shaped piece is not completely submerged in gas, that you need to add fuel. This whole design is IMO ridiculous. Just have a gas cap without this extra nonsense of strings & U-shaped pieces. If the user can't use a flashlight to look in the tank & see the level, then they should hire a lawn service.

So, NO plastic wrap for me. A friend of mine suggested just placing the plastic wrap (or better a zip lock bag) over the hole & use rubber bands to keep it on and seal any outside condensation from entering. IMO, this is just too much of a hassle. If you want to take this to extremes, take a good size piece of plastic wrap. Place it over the entire tightened gas cap, & use an appropriately sized rubber band to seal it to the top of the gas tank's tube.

If you disagree, please post with something other than just stating that gas caps are not airtight & allow moisture through. You should read the article, "THE MYTH OF CONDENSATION IN FUEL TANKS"

The Myth of Condensation in Fuel Tanks

www.ifish.net

In 57 years of using every conceivable kind of lawn equipment, I have NEVER had a problem with water in a gas tank. NEVER. And the only thing I've ever done is take the OEM cap off, fill the tank, and put the OEM cap back on. No plastic wrap, no rubber bands, only using the OEM caps. I do try to keep the tank full on all my equipment, refilling after every use, especially when the machine is going to sit idle more than a few hours. As for not being much water in air at 100% humidity, stand out in the rain sometime and then tell me that with a straight face. ;-) But, in the small confines of a full fuel tank, there's not enough to worry about. IMO of course.

Dec 16, 2023#28

Moparjoe499

Cajun power said:
the myth? lol....with years of proof that this is no myth you are going to expect anyone to accept that water ingress into fuel tanks is not a thing?

Lets start with some basics. gasoline is generally not water attracting..but the gasoline sold and used by almost all mower owners contains alcohol, which does attract water.

the cap bs and the volume bs. A rest, your assumption is that the volume is too small to make a difference and that the cap vent is either too small or that is provides some kind of one way valve protection against water vapor/condensation. So several things: 1) the tank vent is designed to release pressure build in the tank AND also to PREVENT negative pressure (vacuum), so it really is a two way valve. It's designed to be an "OPEN SYSTEM" operating to prevent fuel vapor from building up dangerous high pressure in the tank and also preventings a negative pressure a vacuum in the tank as the engine is operating. Whether this is a gravity fed fuel engine or a pump fed fuel engine, the design is the same. It's a two way valve. And this also occurs IN STORAGE. Because you see, the temperature ambient is also going to cause fuel vapors to expand and contract. And thus even in storage, this valve is constantly moving from open to close, close to open..ever so slightly, but over time, yes, this is going to allow water vapor from the atmosphere (AND CONDENSATION THAT FORMS RIGHT AT THE EDGES OF THAT VENT) to be entrapped and to enter the tank. Water vapor is heavier than fuel, and heavier than fuel vapor..so you have a density issue and this results in fuel vapor going to the bottom of the tank, below fuel. In this area, it accumulates because it cannot escape the lighter density of fuel vapor and fuel liquid on top. Over TIME, this also happens with fuel cans that you use to fill your fuel at the pump. When you open the cap on your portable fuel tank, you are allowing the inrush of fuel from the pump into a quite large opening..it is during this moment when you actually have a very interesting water vapor introduction into the fuel and into the fuel can. Also, one must understand that even at fuel stations, there is a certain amount of water contamination as well. Especially for gasoline sold as alcohol mix. For most vehicles, this small amount of water/water vapor is not really a problem, because auto engines are actually engineered and designed to operate with small amounts of water contamination and still be reliable. However for small engines, air cooled, small amounts of water/water vapor has a much greater impact over time.
Here is an easy experiment you can prove for yourself.

fill your mower tank half full with gas. let it sit for 3 months over the winter. At 3 months, drain the tank completely in a glass mason jar. Notice the fuel-water separation. That is just reality.

now the argument about how much damage can happen with water in fuel? that's a separate question, but important nonetheless. Over time, especially with long storage fuel, water becomes a problem associated with rust and corrosion and also tends to cause fuel lines to become brittle or to collapse internally. Some fuel filters also have different metal components and water creates dissimilar metal corrosion internally, just as it will do with carbs...it's the water that becomes the ion transport, not the fuel...almost all carb contamination from corrosion is caused by water/water vapor. what can you do about it? again, another separate question. It's actually a good practice to NOT STORE Fuel in a tank or a carb for long periods. I do this by emptying the tank and running the engine until it starves from fuel and then I open the carb and allow it to dry, and open the fuel lines too. I smoke the head cylinder with a little motor oil, and then put it all back together. When it comes out of storage, the tank is filled with fresh fuel, and I drain about a 1/2 pint of it out of the fuel line right before the carb...into a glass mason jar. I look for contamination and water vapor. because you see EVEN IN AN EMPTY FUEL TANK< WATER VAPOR CAN HAPPEN. it's a combination of hot/cold weather and that tank vent which is a two way valve...water Can and does accumulate there even when it's empty. This is particularly true for the deep south where high humidity is a year wide environmental reality.

If anyone is getting that much water in their tank, they should check their gas can for water. Don't keep to much gas stored and don't leave the gas can outside. I sold a coworker a push mower. She uses it and comes to work the next day and yells me the mower I sold her quit running. I go to her home and drain water out of the tank. I look for her gas can and find it sitting by her home. The gas can had water in it.

Dec 16, 2023#29

Moparjoe499

farmerdave1954 said:
In 57 years of using every conceivable kind of lawn equipment, I have NEVER had a problem with water in a gas tank. NEVER. And the only thing I've ever done is take the OEM cap off, fill the tank, and put the OEM cap back on. No plastic wrap, no rubber bands, only using the OEM caps. I do try to keep the tank full on all my equipment, refilling after every use, especially when the machine is going to sit idle more than a few hours. As for not being much water in air at 100% humidity, stand out in the rain sometime and then tell me that with a straight face. ;-) But, in the small confines of a full fuel tank, there's not enough to worry about. IMO of course.

There is enough alcohol in today's gas to burn up the small amount of water. In my opinion, people are not checking their has cans and they are putting water in their mowers.

Dec 16, 2023#30

G

Gord Baker

Shady oak said:
Isn’t condensation caused by the difference in temps between inside the tank, and outside, with a little bit of humidity thrown in? Condensation doesn’t leak in through a gas cap. Asking for a friend!

Yes.

Dec 16, 2023#31

ILENGINE

ChiefH said:
I do not know why you get so much water in your gas chain saw tanks. I have one chain saw, one backpack blower, one hand held blower, one line trimmer, two walk behind lawn mowers, one shredder-chipper, one snow thrower, and I do not get water in any of the tanks. I DO however, refill the tank after use so that the tank has little room for air (ever air with moisture). I use Sta-Bil in all of my straight gas containers, and 2-cycle oil in my mix gas containers. I do not seem to get moisture in my storage containers. I live in a summer time humid area (Shenandoah Valley, Va.)

My dad has his saws in another storage building 10 feet away and never has water problems. there are several factors leading to the condensation issues with my chainsaws, but the statement was to prove that condensation does occur.

Dec 16, 2023#32

G

Gord Baker

Condensation does not come from Outside the Tank, but forms on the sides of the INSIDE of the tank from any moisture laden air that is already inside a NONvented tank. Done with this nonsense. Keep your tanks Full and rotate often.

Dec 16, 2023#33

Hammermechanicman

Dec 16, 2023#34

Moparjoe499

farmerdave1954 said:
In 57 years of using every conceivable kind of lawn equipment, I have NEVER had a problem with water in a gas tank. NEVER. And the only thing I've ever done is take the OEM cap off, fill the tank, and put the OEM cap back on. No plastic wrap, no rubber bands, only using the OEM caps. I do try to keep the tank full on all my equipment, refilling after every use, especially when the machine is going to sit idle more than a few hours. As for not being much water in air at 100% humidity, stand out in the rain sometime and then tell me that with a straight face. ;-) But, in the small confines of a full fuel tank, there's not enough to worry about. IMO of course.

You are correct. If someone can convince people to replace the cap to stop water from getting into their gas tank, they will replace it. They better check their gas cans for water. It is really hard to fix stupid.

Dec 16, 2023#35

Moparjoe499

ChiefH said:
I do not know why you get so much water in your gas chain saw tanks. I have one chain saw, one backpack blower, one hand held blower, one line trimmer, two walk behind lawn mowers, one shredder-chipper, one snow thrower, and I do not get water in any of the tanks. I DO however, refill the tank after use so that the tank has little room for air (ever air with moisture). I use Sta-Bil in all of my straight gas containers, and 2-cycle oil in my mix gas containers. I do not seem to get moisture in my storage containers. I live in a summer time humid area (Shenandoah Valley, Va.)

STA-BIL is a money scam. Look at the ingredients. You can buy a gallon of PETROLEUM DISTILLATES or MINERAL SPIRITS to add to the gas tank. Stupid people never learn anything.

Dec 16, 2023#36

S

SamB

Rivets said:
Boy I hit a nerve. I just call them as I see them. I may not be right, but you also could be wrong. Let others who read this thread make their own decisions when they get both sides of this theory.

Top quality info from you, Rivets, always. Don't sweat the trolls. Water WILL get into fuel tanks in many ways. My late father-in-law's ztr mower's carbs bowl was full of rust. Never spent a night outside. Always new fuel, too.

Dec 17, 2023#37

B

bertsmobile1

Moparjoe499 said:
A couple weeks ago I started a snowblower that had been sitting in my garage for 6 years. I ran it for 5 minutes without any problems. People get all anal about the fuel worrying about if the cap has a good seal, draining the tanks dry, putting fuel stabilizer in the tanks, ect, ect. Unless you are purchasing 100% gasoline, then it already has 10% alcohol in it and the water will be burned when it is running.

Fuel stability isa random thing
I live 500 yards from the landord.
is old house is by the river & the new house is up the hill 60' to be above the flood line.
Between us is open pasture
My fuel keeps fine for over a year , his goes off in 2 weeks . It is all about your local microclimate , shed type, max & min temps & dew points.
95% of people will be fine but because of the testimonials from that 5% another 75% get sucked into using them
If you do need them then most work really well as for the rest of us they just lighten the wallet .

Dec 17, 2023#38

B

bertsmobile1

Shady oak said:
Isn’t condensation caused by the difference in temps between inside the tank, and outside, with a little bit of humidity thrown in? Condensation doesn’t leak in through a gas cap. Asking for a friend!

No it is simply because the moist air that came in cools down overnight.
As the air cools it capacity to hold moisture drops so the water forms droplets & runs down the side of the tank

Dec 17, 2023#39

Moparjoe499

SamB said:
Top quality info from you, Rivets, always. Don't sweat the trolls. Water WILL get into fuel tanks in many ways. My late father-in-law's ztr mower's carbs bowl was full of rust. Never spent a night outside. Always new fuel, too.

People need to check their gas cans for water. Take a glass jar and pour some in gas in it. The water will be on the bottom. People will leave their gas can outside and expect their mowers to run. Meryl Haggard sang a song, Rainbow Stew. When they find out how to burn water and the gasoline car is gone.

Dec 17, 2023#40

ILENGINE

Moparjoe499 said:
People need to check their gas cans for water. Take a glass jar and pour some in gas in it. The water will be on the bottom. People will leave their gas can outside and expect their mowers to run. Meryl Haggard sang a song, Rainbow Stew. When they find out how to burn water and the gasoline car is gone.

Most of the time people are putting water into their gas cans and don't even know. Ethanol in fuel contains a certain percentage of water left from the manufacturing process. That water may be stable at 70 degrees but could phase separate at 30 degrees.

Years ago before ethanol people would leave their vented gas cans out and would either condense water from temperature air exchange or just flat get rain in them. Now with ethanol the alcohol makes it it's mission to draw water from the air every change it gets being it from open vent container or other means.

Dec 17, 2023#41

Moparjoe499

ILENGINE said:
Most of the time people are putting water into their gas cans and don't even know. Ethanol in fuel contains a certain percentage of water left from the manufacturing process. That water may be stable at 70 degrees but could phase separate at 30 degrees.

Years ago before ethanol people would leave their vented gas cans out and would either condense water from temperature air exchange or just flat get rain in them. Now with ethanol the alcohol makes it it's mission to draw water from the air every change it gets being it from open vent container or other means.

People will leave their gas cans outside and expect their mowers to run. If you use gas out of a can often enough, their shouldn't be any water in the can unless you are getting it from the gas station.

Dec 17, 2023#42

Hammermechanicman

My 1989 motorhome with a Qjet carburetor sat for 5 years in an unheated barn with E10 gas in it. Fired up and ran fine. I have customers who leave E10 gas in a snowblower for 6 months and it trashes the carb.
I don't know much but I do know ethanol in gas makes me money.

Dec 17, 2023#43

ILENGINE

Moparjoe499 said:
People will leave their gas cans outside and expect their mowers to run. If you use gas out of a can often enough, their shouldn't be any water in the can unless you are getting it from the gas station.

But that is the thing. You are getting it from the gas station. Ethanol enriched fuel contains water

Dec 17, 2023#44

G

Gord Baker

bertsmobile1 said:
No it is simply because the moist air that came in cools down overnight.
As the air cools it capacity to hold moisture drops so the water forms droplets & runs down the side of the tank

You are correct Shady. In a partially filled tank, the air does not 'come in' overnight. What air is in the tank remains until more contents is used. Ethanol absorbs water in the fuel and condensate and remains at the bottom of the tank with it. Don't totally empty a partially filled container into your small engine. Always use a funnel with filter to take out the lumps.

Dec 17, 2023#45

Moparjoe499

Hammermechanicman said:
My 1989 motorhome with a Qjet carburetor sat for 5 years in an unheated barn with E10 gas in it. Fired up and ran fine. I have customers who leave E10 gas in a snowblower for 6 months and it trashes the carb.
I don't know much but I do know ethanol in gas makes me money.

I have a snowblower in the garage. I have not started it in 6 years. Choked it, pulled it 2 times and it runs. People have water in their gas cans.

Dec 18, 2023#46

upupandaway

Gord Baker said:
Air contains Moisture. A Fuel Tank MUST be vented to allow fuel to flow out, thus fresh air is being constantly drawn into the tank.

True. Just look at a plastic gas can when temp drops 20deg or rises 20 deg. The gas can shrinks or bulges- that would vent or draw in air if it wasn't air tight.

Dec 18, 2023#47

Moparjoe499

upupandaway said:
True. Just look at a plastic gas can when temp drops 20deg or rises 20 deg. The gas can shrinks or bulges- that would vent or draw in air if it wasn't air tight.

And stop leaving your gas can outside.

Dec 19, 2023#48

upupandaway

Moparjoe499 said:
And stop leaving your gas can outside.

Thing is, leaving it in the garage has the same effect, just not so bad.

Dec 19, 2023#49

Moparjoe499

upupandaway said:
Thing is, leaving it in the garage has the same effect, just not so bad.

It won't make any difference if the gas cap seals or not. If you are using the gas fast enough out of the tank, people don't have to get all anal about water.

Dec 25, 2023#50

C

CraftsmanFlaws

Moparjoe499 said:
It won't make any difference if the gas cap seals or not. If you are using the gas fast enough out of the tank, people don't have to get all anal about water.

From you other long post here, it sounds like you have a lot of knowledge about how gasoline (more, it's the ethanol) attracts water. I don't agree w/you that covering a vented gas cap completely with plastic wrap & then rubber bands won't keep moisture out. It HAS to.

I, unfortunately, thought I bought enough gas to completely fill the tractor tank; but, it didn't & I am a gallon short. I was just tired & cold, & decided to simply leave it this way. According to some of the posts, a tractor gas tank holds such a finite amount of gas, it doesn't make a great deal of difference. Prior, I added Seafoam to the gas, ran it a few minutes, so don't you believe it will prevent rubber & carb damage over the winter?

Dec 26, 2023#51

Moparjoe499

Gord Baker said:
You are correct Shady. In a partially filled tank, the air does not 'come in' overnight. What air is in the tank remains until more contents is used. Ethanol absorbs water in the fuel and condensate and remains at the bottom of the tank with it. Don't totally empty a partially filled container into your small engine. Always use a funnel with filter to take out the lumps.

CraftsmanFlaws said:
From you other long post here, it sounds like you have a lot of knowledge about how gasoline (more, it's the ethanol) attracts water. I don't agree w/you that covering a vented gas cap completely with plastic wrap & then rubber bands won't keep moisture out. It HAS to.

I, unfortunately, thought I bought enough gas to completely fill the tractor tank; but, it didn't & I am a gallon short. I was just tired & cold, & decided to simply leave it this way. According to some of the posts, a tractor gas tank holds such a finite amount of gas, it doesn't make a great deal of difference. Prior, I added Seafoam to the gas, ran it a few minutes, so don't you believe it will prevent rubber & carb damage over the winter?

Its freakin gasoline. It has 10% alcohol in it. Any condensation will be burned in the cylinder. Anyone who cuts grass often enough will buy gasoline often enough that the can won't get any water in it. Stop leaving your damn freaking gas can outside. I have ran across this problem before and people wonder why their mower won't run. Stupid people never learn.

Dec 30, 2023#52

Moparjoe499

CraftsmanFlaws said:
From you other long post here, it sounds like you have a lot of knowledge about how gasoline (more, it's the ethanol) attracts water. I don't agree w/you that covering a vented gas cap completely with plastic wrap & then rubber bands won't keep moisture out. It HAS to.

I, unfortunately, thought I bought enough gas to completely fill the tractor tank; but, it didn't & I am a gallon short. I was just tired & cold, & decided to simply leave it this way. According to some of the posts, a tractor gas tank holds such a finite amount of gas, it doesn't make a great deal of difference. Prior, I added Seafoam to the gas, ran it a few minutes, so don't you believe it will prevent rubber & carb damage over the winter?

Seafoam is a money scam. Look up seafoam msds. You can buy the ingredients in a gallon at a hardware store.

Dec 30, 2023#53

ILENGINE

Moparjoe499 said:
Seafoam is a money scam. Look up seafoam msds. You can buy the ingredients in a gallon at a hardware store.

Seafoam prior to around 2004 was some good stuff. But around that time they reformulated it due to EPA constraints and the new stuff is garbage.

Dec 30, 2023#54

Moparjoe499

ILENGINE said:
Seafoam prior to around 2004 was some good stuff. But around that time they reformulated it due to EPA constraints and the new stuff is garbage.

PETROLEUM DISTILLATES IS THE MAIN INGREDIENT. YOU CAN BUY IT AT ANY HARDWARE STORE.

Dec 30, 2023#55

ILENGINE

Name calling in PM's are uncalled for.

Dec 30, 2023#56

G

GrumpyCat

I can't read 6 pages of this thread.

Small engine gas caps breathe. Necessary to let air in when gasoline is used by the engine. When temperature changes some air in the tank leaves when it warms, fresh air enters when it cools. Ethanol in the gasoline extracts moisture from the air in the tank.

Moisture in ethanol-laced gasoline does not settle to the bottom until the saturation point is reached. Ethanol will hold a certain amount of water in solution, then the white cloudy stuff starts appearing and one has significant problems. This is called phase separation. Many treatments "fix" this by providing more of what ethanol does, increasing the capacity to carry water in solution. Isn't really a fix although it might get the water out of your gas tank if your engine can run on the resulting swill.

Water in ethanol gasoline is still water in one's gasoline. Engine running may not be affected much but the water combined with ethanol is corrosive.

Automotive fuel systems with vapor recovery systems do a very good job of keeping moisture out of gasoline.

Dec 30, 2023#57

Moparjoe499

GrumpyCat said:
I can't read 6 pages of this thread.

Small engine gas caps breathe. Necessary to let air in when gasoline is used by the engine. When temperature changes some air in the tank leaves when it warms, fresh air enters when it cools. Ethanol in the gasoline extracts moisture from the air in the tank.

Moisture in ethanol-laced gasoline does not settle to the bottom until the saturation point is reached. Ethanol will hold a certain amount of water in solution, then the white cloudy stuff starts appearing and one has significant problems. This is called phase separation. Many treatments "fix" this by providing more of what ethanol does, increasing the capacity to carry water in solution. Isn't really a fix although it might get the water out of your gas tank if your engine can run on the resulting swill.

Water in ethanol gasoline is still water in one's gasoline. Engine running may not be affected much but the water combined with ethanol is corrosive.

Automotive fuel systems with vapor recovery systems do a very good job of keeping moisture out of gasoline.

So in all reality, since the gas cap has a vent hole to allow the gas to be drawn out of the tank , then it won't matter if the cap has a good seal or not. That's a good point.

Dec 30, 2023#58

R

Rivets

Politics are not part of this forum as well as your yelling in all caps. I thought you might be an intelligent guy until you last few posts. Now I’m questioning my aged brain. Think this thread has run its course.

Dec 30, 2023#59

Scrubcadet10

Joe, you're out of line. You get one more chance.

Dec 30, 2023#60

Scrubcadet10

Well, you had a chance until you messaged me
Bye.

Dec 30, 2023#61

R

Rivets

Thank you.

Jan 6, 2024#62

J

jbugj

Rivets said:
Politics are not part of this forum as well as your yelling in all caps. I thought you might be an intelligent guy until you last few posts. Now I’m questioning my aged brain. Think this thread has run its course.

but then, this thread is about 'caps'...

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Gas Caps do seal out any condensation from entering the gas tank, despite the arguments here saying they do not

The Myth of Condensation in Fuel Tanks

The Myth of Condensation in Fuel Tanks

The Myth of Condensation in Fuel Tanks

The Myth of Condensation in Fuel Tanks

The Myth of Condensation in Fuel Tanks

The Myth of Condensation in Fuel Tanks

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