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

[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

 

[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,

 

[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.

 

[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.

 

[ILENGINE]

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

 

[Scrubcadet10]

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.

 

[CraftsmanFlaws]

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.

 

[Scrubcadet10]

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

 

[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 .

 

[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.