Date:         Wed, 19 Jan 2011 10:35:40 -0500
Reply-To:     Derek Drew <derekdrew@DEREKMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Derek Drew <derekdrew@DEREKMAIL.COM>
Subject:      Charcoal Canister Dangers and Docs
Content-Type: text/plain; charset="us-ascii"; format=flowed

I have been warned by people that there is a significant danger when
plumbing the hoses related to the charcoal canister that if you allow
the vent hoses from the gas tank to be crushed or blocked, then the
gas tank can self destruct after a drive when it cools down by
sucking itself into a ball.

Apparently, when the gas tank is plastic as in syncros, it has a
chance of not being destroyed by this but will just pop back into
shape, as happened to Karl Mullendore. However, you cannot start the
vehicle until the suction condition is resolved.

Understanding the charcoal canister system so you can properly plumb
it in a conversion is a pain because the documentation is so
confusing and scattered.

In fact, it seems like one of the Bentley pages isn't even in Bentley
at all, but is glued onto the relay box in the engine compartment.



http://lh3.ggpht.com/_tcfhlV6J8Y0/TS3l7xJqCPI/AAAAAAAAAng/xU6-D5UY37g/s912/DSC01277.JPG



This picture is from the 2.1L engine bay. I am sure many people
reading this has seen it many times.

Germans have written me for intstructions on how to hook up the
charcoal canister, and I was very disappointed to tell them I
couldn't make heads of tails out of it because I didn't think to look
around for a Bentley page inside the engine compartment.

I have heard of cases where the charcoal canister goes bad and
something like a screen breaks and bits of charcoal travel through
the fuel hoses in the vehicle and destroy the fuel system.

If charcoal bits travel out of the canister, they can only go either
into the gas tank, where they would be filtered, or into the intake
air distributor, where they would enter the air supply and make their
way to the injectors possibly. Perhaps someone who had a failure of
the charcoal canister with disasterous results could comment on what happens.

These results sound bad enough that if I decide to connect my
charcoal canister, I'd be tempted to put little fuel filters on every
hose going into or out of it after hearing of these stories. But it
also seems possible that if the fuel filters got clogged, one could
end up with a crumpled up gas tank and be back to square 1.

If you are ever doing a conversion and want the option to retain the
charcoal canister and understand its function and hoses so you can
connect it correctly to the new engine, you might want to print this
out and insert it into your Bentley at page 20.33. In addition, you
should check Bentley pages 20.34 and maybe 24.24b, and maybe page 12
of the Digifant I/Digifant II ProTraining manual from 12/88. These
page references are oriented toward digifant syncros so there are
some others besides this.

You could annotate page 20.33 to identify a little better the
function of each hose so you can figure out what the heck is supposed
to be happening.

A crude annotated page is here:




http://lh3.ggpht.com/_tcfhlV6J8Y0/TTbxUqWCKaI/AAAAAAAAAuo/G3p5lA6DfAI/s720/Vaanapaloozaaaa%20018.jpg


which you are welcome to print out or transscribe. On the computer, I
couldn't read this until I opened the picture in my web browser and
then VIEW > ZOOM > 200%. The notes are trying to say this:

1. The little hose at the top of the canister is where the gas vapors
from the gas tank are entering the canister.

2. The big hose at the bottom of the canister is where the canister
gets its fresh air supply, the supply being provided by a hose that
runs to a point after the air filter in the engine compartment.

3. The big hose at the top is the exit point where the gas vapors are
sucked away to go back into the engine for combustion.

4. In the engine compartment there is a valve in the forward right
corner of the engine compartment with one big hose and two little hoses.

5. The big hose I just referred to in #3 and #4 is supplying the gas
vapors from the carbon canister to this valve.

6. One of the smaller hoses routs the air into the engine intake air
for combustion, and the other of the smaller hoses opens the valve
and operates it via vacuume pressure it gets from the distributor.


_______________________________________________
Derek Drew
Founder, ConsumerSearch.com
Washington DC / New York
derekdrew@derekmail.com
202-966-7907 (Call the number at left normally)
                 (alt/cell for diligent calling only): 703-408-1532