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Date:         Mon, 3 Mar 2008 21:19:31 -0500
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
Comments:     RFC822 error: <W> MESSAGE-ID field duplicated. Last occurrence
              was retained.
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: Calif 2008 emissions fuel tank pressure testing?
Comments: To: John Bange <jbange@GMAIL.COM>
In-Reply-To:  <6da579340803031753s610bd98fsaa45124b9197a694@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"

When the engine is not running, or at idle, the tank should be sealed. Fumes are collected in the carbon canister but should not be released to the atmosphere. When the engine is off idle, the valve for the carbon canister should open and the fumes vented into the air filter and burned off in the engine. As fuel is sucked down, replacement air should also be drawn in through this valve. You should be able to hear the valve click open when the throttle is opened. One of the problems with most engine conversions is that the throttles are not ported to properly operate this valve.

Personally, I do not think it is unreasonable for the fuel system to remain tight and prevent evaporating fuel from just venting into the air. By 1971 almost all cars had some type of vapor recovery system. If this test finds leaky systems that need to be fixed, then it is serving the intended purpose even if the program is not perfect.

When the tank is filled, it not vented through the carbon canister. The actual vent is through the filler and the vapor recovery nozzles are supposed to collect those fumes and bring them back to the stations tank.

Dennis.

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Bange Sent: Monday, March 03, 2008 8:54 PM To: vanagon@GERRY.VANAGON.COM Subject: Re: Calif 2008 emissions fuel tank pressure testing?

> Maybe I'm operating under the wrong misconception, but I don't understand > how a tank can be expected to hold pressure when it presumably vents thru > the charcoal canister to let the air out while being filled. Can someone > explain? >

Yeah, you got me. The guy at the test place didn't explain it very thoroughly, plus I wasn't listening very well. All I know is it involves pressurization (vacuum?) of some sort, and takes 15-20 minutes to test. Perhaps a charcoal evap filter only should be able to pass a certain volume of air in a given time, and if too much can pass, that indicates a leak?

-- John Bange '90 Vanagon - "Geldsauger"


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