TheSamba.com :: View topic - Evaporative Emission Control EVAP/Charcoal, Carbon Canister

Wed Jul 02, 2014 10:27 am

To link to this thread
Code: [url=http://www.thesamba.com/vw/forum/viewtopic.php?t=599709&start=0&postdays=0&postorder=asc&highlight=]Evaporative Emission Control EVAP/Charcoal, Carbon Canister[/url]

Tcash wrote: I find it interesting, that the canister must be replaced every 30k.

[quote="raygreenwood"] Tcash wrote: I find it interesting, that the canister must be replaced every 30k. quote]

Its not hard to understand. Modern canisters generally should be replaced by about 70K miles. Early canisters suffered from not only mechanical issues like what SGKent noted with the plastics breaking down, rust etc......but mainly the effectiveness of the carbon inside.

The filling is a specific grade and size of coconut carbon (an activated carbon made from partially combusted and treated coconut husk/bark/fiber). It can only absorb so much vapor before it is no longer effective at absorbing and re-emitting vapor and must be recycled.

In reality, the carbon absorbs a portion of fuel that can never be re-evaporated. This fuel vapor condenses into pores in the carbon that are so small that the relative surface tension on the core amount of fuel absorbed is too great for basic evaporation from air being pulled through the granules by the vacuum line loop to the engine to happen. This happens probably in the first few days of use. However....the outer surface area is so great on the carbon that it works great for long time to capture most fuel vapors and re-evaporate them. In the long run though....it will sooner or later reach a saturation point where the carbon no longer can absorb anything. Most of what causes this maximum saturation is water vapor/moisture creating in effect...a gel with the fuel vapors.

Recycling in our case.....means getting a new canister. This is because the only way to get full vapor release and really clean out the carbon is to use high pressure, high heat and superheated steam. This is a recyclable material, the solvents contained can be recaptured and there is an industry for it.

Oh...by the way...the saturated carbon...technically is listed as a hazardous waste. If you were a business../you would have to either recycle it or have it disposed of along with your other hazardous wastes in as permit waste stream. But....you can legally dispose of it after letting it dry out...in your household trash (yes....its a loophole in the laws).

You can use the tried and true method of refilling and otherwise mechanically sound canister with fish tank carbon....which while it looks the same.....is nowhere near being exactly the same or as long lasting....but will work fine and is cheap.

sorry for the long post...but I deal with this type of stuff as part of my job. Though it might be of interest. Ray

1970 EVAP System
http://www.thesamba.com/vw/archives/manuals/70vwprogram/page23.jpg
http://www.thesamba.com/vw/forum/album_page.php?pic_id=1258395
http://www.thesamba.com/vw/forum/album_page.php?pic_id=1258394

1970 Pick Up EVAP System
http://www.thesamba.com/vw/forum/viewtopic.php?t=6...highlight=

1971 EVAP System

1972 EVAP System

1973 EVAP System

Maybe 1972-73 non US - Canada.

1975 Rubber filler neck FI

1978 gas tank filler parts

70-71 charcoal hose diagram
http://www.thesamba.com/vw/forum/album_page.php?pic_id=1050925

1977 Charcoal canister
http://www.thesamba.com/vw/forum/album_page.php?pic_id=1393130

1978 Charcoal canister
https://www.thesamba.com/vw/gallery/pix/1422323.jpg
https://www.thesamba.com/vw/gallery/pix/1422322.jpg
https://www.thesamba.com/vw/gallery/pix/1422846.jpg
https://www.thesamba.com/vw/gallery/pix/1422845.jpg

______________________________________________________________________________________________________________________
1973 Emission Control System booklet

Wed Jul 02, 2014 10:31 am

If you like to top off your fuel tank, this saturation will happen at an accelerated rate.

Wed Jul 02, 2014 11:11 am

Interesting! Makes me wonder about how I pass smog checks with a 30+ year old canister...probably not that important, anyway. So to further the fish tank charcoal/carbon theory, what about plain BBQ charcoal? Maybe worse than the fish tank stuff?

Are alternate charcoal canisters available?

Wed Jul 02, 2014 11:44 am

Typically you "can" have problems during emmisions testing with our older style cannisters...but generally dont....because they are in conztant flow through operations on our vehicles. This means that from the moment you start the engine until you turn it off there is air being sucked through the grid.
On newer vehicles there is a relay and vacuum switch that only runs air through the canister during warm up.
This constant flow through of old systems is one of sever reasons why they are required to not test your vehicle until it is fully warmed up and has been at least idleing for a while. It pretty much empties most of the vapor that could foul testing.

No you cannot use barbecue charcoal. It must be ACTIVATED charcoal. There are numerous kinds and blends... silverized....blended with potassium permangenate etc.

Short of minor plumbing details they all work the same. You can use a canister from any vehicle that you can make fit. Ray

Wed Jul 02, 2014 8:16 pm

raygreenwood wrote: On newer vehicles there is a relay and vacuum switch that only runs air through the canister during warm up.

well, sort of 8)

Sun Jul 06, 2014 6:06 pm

Carbon Canister Refresh - Howto

Tue Dec 23, 2014 5:38 pm

The Fuel Flap makes this a pre 74 fuel tank ventilation system (minus the extra vent in the filler system) for a Type 1 upright engine depicted by the air cleaner.

Pic courtesy of peteandvanessa

http://www.thesamba.com/vw/forum/album_page.php?pic_id=1235211.jpg

busdaddy wrote: Great drawing, but it doesn't include that evil 72/73 center vent and the elbow that leads to the filler neck, a great pre production artists conception of what next years vapor system theory including the separator/condensor bulbs looks like though :D
busdaddy wrote: Tcash wrote: BD should I delete it?
No I don't think so, it shows the vent system all later buses use, only 72/73's with the gas door use the extra vent in the filler system, it applies to all 72+ buses as far as venting goes.

Tue Dec 23, 2014 7:01 pm

Great drawing, but it doesn't include that evil 72/73 center vent and the elbow that leads to the filler neck, a great pre production artists conception of what next years vapor system theory including the separator/condensor bulbs looks like though :D

Tue Dec 23, 2014 7:14 pm

BD should I delete it?

Tue Dec 23, 2014 8:50 pm

Might be the European version for certain years?

Tue Dec 23, 2014 10:56 pm

Tcash wrote: BD should I delete it?
No I don't think so, it shows the vent system all later buses use, only 72/73's with the gas door use the extra vent in the filler system, it applies to all 72+ buses as far as venting goes.

Wed Dec 24, 2014 7:38 am

I need to do this on my 78 but couldn't put my hands on the right kind of pellets last time and gave up. Anyone have a good source for the pellets?

Wed Dec 24, 2014 8:18 am

activated charcoal. That means steam treated. We got ours from a local aquarium. These might work, I can't see inside the bag online.

http://www.amazon.com/gp/product/B000YIWT0M/ref=pd...B0034Q6MFY

SGKent wrote: jpstewart19 wrote: I didn't even think to use granules. I actually found new charcoal pellets that looked exactly like what I dumped out. They were in little mesh bags I needed to cut open. I assumed what was in there was original. Which do most people use?

we used bulk. Any steam activated charcoal will do. The steam eats little holes and pores in it so it has room to store fumes. There is a flame trap filter on the small hose end that turns to goo over the years. The only thing we could find like it was a scotch green pad (red actually) that is designed for chemicals. I cut a little piece of that and used it as the filter / trap.

Wed Dec 24, 2014 11:04 am

Actually activated carbon is not ACTIVATED by steam....its regenerated by steam as part of a multi-step process. This means that its recycled (getting vapors and contaminants out to reuse the carbon).....by using steam cracking after drying and then heating in an inert atmosphere.

Generally activation is done by an acid etch process, then vacuum cleaning and in medical grades. ...this carbon is the steam cracked and vacuumed again.

Also as I noted quite a while back in one of these threads. ...in reality not "any activated" carbon product will restore full factory level of functionality.
Activated carbon is graded by size type for its response to contaminant absorption. Granules over a certain size work best for absorbing impurities in liquids....while powders of certain, sizes work better for gas and vapor.

That being said....any of them as others have noted...will work better than no carbon at all for restoring a canister. The fish tank type carbon is actually a medical carbon. It has to be really clean. But it should not matter for this use. Ray

Wed Dec 24, 2014 11:53 am

There is a lot of information overload on EVAP canisters out there.

If your system has all the hoses and clamps intact, the EVAP canister is not holed, then your system is recycling 95% of the gas fumes or better, even with old activated carbon. IMHO, it's a waste of time to chase the incremental last bit of vapor with some of the schemes proposed.

Wed Dec 24, 2014 12:25 pm

My original canister was not salvageable. I ordered one from VW and got this cylindrical modern day model. It has the same 3 hose connections as the original and I was able to use the existing hanger.

I need to fit a barb on my oil bath to make the final connection.

1970 Westfalia 1600

Wed Dec 24, 2014 1:35 pm

busdaddy wrote: Tcash wrote: BD should I delete it?
No I don't think so, it shows the vent system all later buses use, only 72/73's with the gas door use the extra vent in the filler system, it applies to all 72+ buses as far as venting goes. ahhh, found this one from mr. Ratwell!

Wed Dec 24, 2014 6:29 pm

force3g wrote: I ordered one from VW and got this cylindrical modern day model. It has the same 3 hose connections as the original and I was able to use the existing hanger.

To bad you did not roll it a little further toward you when you took the picture so you could read the part number. It looks like 175-201-801-A.
Tcash

Wed Dec 24, 2014 6:52 pm

Like this maybe

http://www.germansupply.com/home/customer/product.php?productid=17726&cat=&page=1

Wed Dec 24, 2014 9:30 pm

To bad you did not roll it a little further toward you when you took the picture so you could read the part number. It looks like 175-201-801-A.

My bad Tcash, the pic is a couple of years old. You are correct on the part number.