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I've just recently bought a Snapper Pro S150xt. Im wondering what the EVAP Canisters actually do? My dealer didn't really explain them to me. Here are two pictures I took of them (I have to fuel tanks one the mower and each tank has a canister this is just one they are both alike)

The canister (actually a charcoal canister) is an evaporative emissions control device. That is, it catches the fumes from the gas evaporating in the fuel tank and then at controlled times, feeds them into the engines intake so they are burnt up and not allowed to escape into the atmosphere.:smile:

I don't know how old you are, but you may remember the coffee can under the hood of late 70's and into the 80's vehicles, that is a EVAP canister. The previous poster is correct on how it works and what it does. Just don't overfill the tank and allow raw fuel to get into the canister or you will be replacing it.

Wow, so they are putting these on mowers now huh? When did they start doing that?

Required as of 2011 or 2012. have to have evap canisters, low perm fuel line, non vented fuel caps, florinated fuel tanks if plastic. The extra tall caps you are seeing on the new push mowers have the charcoal canister in the cap.

have seen two evap canisters flooded by raw fuel in the past year. Totally destroys them. supposedly it makes a solid brick out of the charcoal, so it can't vent. I believe some of the new riders don't have an evap canister, but there is a line hooked from the fuel tank to the low vacuum side of the intake, therefore the fuel tank actually operates under a vacuum.

Some are set up to where as you use fuel from the tank, the resulting vacuum pulls the fumes back out of the canister. On others the intake vacuum pulls the fumes out of the canister and are burnt in the engine.

Mine has the vac hose in the top of the tank hooks to the intake.

(( cowboy up and get over it ))

ILENGINE said:

Required as of 2011 or 2012. have to have evap canisters, low perm fuel line, non vented fuel caps, florinated fuel tanks if plastic. The extra tall caps you are seeing on the new push mowers have the charcoal canister in the cap.

have seen two evap canisters flooded by raw fuel in the past year. Totally destroys them. supposedly it makes a solid brick out of the charcoal, so it can't vent. I believe some of the new riders don't have an evap canister, but there is a line hooked from the fuel tank to the low vacuum side of the intake, therefore the fuel tank actually operates under a vacuum.

Some are set up to where as you use fuel from the tank, the resulting vacuum pulls the fumes back out of the canister. On others the intake vacuum pulls the fumes out of the canister and are burnt in the engine.

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Sounds like something that would better serve in the trash can.

phcaan said:

Sounds like something that would better serve in the trash can.

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Agreed I would probably bypass it if I had one good thing I dont

I guess its a sign of the times. I believe I read somewhere that even a small push lawn mower gives off more pollutants than a new car.

One interesting sidenote to show how far we have come. I read an article in AutoWeek when Ford came out with the new Boss 302. They said that a 1969 stock Boss 302 just sitting (not running), gave off more pollutants than 200 new Boss 302's driving at 55mph. It's amazing what can be done with modern technology and electronics. I'm sure this is all coming to the lawn mower world eventually (the canister is the start). This will make it more difficult for us old timers to diagnose and repair problems...:smile:

Bruce

Can the EVAP be bypassed?

Brucebotti said:

I guess its a sign of the times. I believe I read somewhere that even a small push lawn mower gives off more pollutants than a new car.

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The question is: How many hours per year does the average mower run compared to a car? If it's 30 hours, that's equivalent to about 1,200 miles a year in a car for average driving. Therefore, mowers don't make significant pollution over all compared to cars. The EPA should have left them alone as not cost effective. Bypassing this junk is a challenge to many tinkerers.

Like the new gas cans. I have one. To pour, I take the spout completely off and use a 10 inch funnel.

Brucebotti said:

I guess its a sign of the times. I believe I read somewhere that even a small push lawn mower gives off more pollutants than a new car.

One interesting sidenote to show how far we have come. I read an article in AutoWeek when Ford came out with the new Boss 302. They said that a 1969 stock Boss 302 just sitting (not running), gave off more pollutants than 200 new Boss 302's driving at 55mph. It's amazing what can be done with modern technology and electronics. I'm sure this is all coming to the lawn mower world eventually (the canister is the start). This will make it more difficult for us old timers to diagnose and repair problems...:smile:

Bruce

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Lab results when taken out of contents can be made to reveal anything and that is before the number crunchers distort the figures so much they bear no relation to reality.
Then you get the true lies, a perfect example that we can all relate to is 1/2 hour exposed to sunlight will destroy all the vitamin C in milk.
This came from the milk carton makers and is true, however if we drank milk for it's vitamin C content we would all die from scurvy .

Mowers contribute almost nothing to enviromental pollution however if you take them into a lab and hook the exhaust up to analytical machines then extrapolate the results to a level that would never be reached in use you can make some amazing conclusions.

Every mower running 24/7 in the USA would pump out the same amount of pollution as 1 hour of take offs & landings at any major domestic airport, but no says boo about that.
In fact a great amount of pride is attached to how much air travel will increase.

How can I bypass the EVAP on my 20 hp field and brush mower. Just put a new one on ad think I could have filled the tank too high and was going over some very
rough ground and could have plugged this new can up too.

John Fitzgerald said:

The question is: How many hours per year does the average mower run compared to a car? If it's 30 hours, that's equivalent to about 1,200 miles a year in a car for average driving. Therefore, mowers don't make significant pollution over all compared to cars. The EPA should have left them alone as not cost effective. Bypassing this junk is a challenge to many tinkerers.

Like the new gas cans. I have one. To pour, I take the spout completely off and use a 10 inch funnel.

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Runtime is irrelevant. Fuel just sits in the gastank 24/7, 365 days whether it's a mower or a car. And even if you drain the gas out of your small engine tools for the winter, most of the fuel evaporation occurs in warm weathers.