Fuel vapors in driver compartment

[oldroadiedog]

I've seen posts on this subject but just want to confirm and get some ideas...

During my engine rebuild the mechanic changed my carb to a Weber 38 DGV. He got rid of the fuel vapor canistor and I have also stripped that vapor hose from under the chassis. So now I've got pretty strong vapors in the driver compartment - especially when the fuel tank is near full. The overflow line and the two larger hoses are in place on the tank which is original and in good condition.

Can I safely run a new vapor line from the original connecting point at the tank (it's a T on the overflow, right?), beside the fuel line under the chassis and then connect directly to the vacum hose (with a T) that runs from the valve cover to the exhaust manifold? I'm pretty sure that's where the orignal line connected from the canistor.

[kwilford]

Originally Posted by oldroadiedog the mechanic changed my carb to a Weber 38 DGV. He got rid of the fuel vapor canistor and I have also stripped that vapor hose from under the chassis. So now I've got pretty strong vapors in the driver compartment - especially when the fuel tank is near full. The overflow line and the two larger hoses are in place on the tank which is original and in good condition. Can I safely run a new vapor line from the original connecting point at the tank (it's a T on the overflow, right?), beside the fuel line under the chassis and then connect directly to the vacum hose (with a T) that runs from the valve cover to the exhaust manifold? I'm pretty sure that's where the original line connected from the canister.

I never have quite figured out WHY some folks remove the cannister. I guess there is a feeling that "pollution" control equipment is BAD, and somehow robs performance. Maybe so in some cases, but when the car depends on it, it is a bit dumb.

The gas tank MUST be vented. Period. If not, it will be pulled into a vacuum when the fuel pump pulls gasoline out of it. So I presume your tank is still vented, but just externally, into the rear of the car, which is causing it to vent fumes into the cockpit. If you hook a vent line up to a vacuum line, the manifold will pull the tank into a vacuum, so that isn't a good idea. The stock arrangement has the canister vent hooked into a tube that connects to the upper throat of the Solex. In truth it pulls a SLIGHT vacuum. You can get the same effect with a Weber by hooking it to the base of the filter housing, DOWNSTREAM of the filter (so the pressure drop across the filter will be the extent of the "vacuum" that vents the tank.

HTH

[oldroadiedog]

Is there an alternative filter to the original canister?

[soybean]

My fuel vapor canistor wasn't on the car when I purchased it, however the vapor line from the tank to the front was still there. When I reran the gas line using steel line, I left the vapor line to the front and added a vent, like the one on the differential, to the end of the vapor line. I don't have any fumes in the car, and the tank is still vented. JM2CW. Jarrell

[kwilford]

Originally Posted by oldroadiedog Is there an alternative filter to the original canister?

Pretty much any charcoal cannister from the late seventies to, well, maybe now, should work. All it needs are two connections. One to vent the tank into, and the other to vent the cannister to the air filter body. If there are three (like the OEM cannister), you can vent the carb fuel bowl (if you have a Weber that has the vent; most don't), otherwise just plug in off.

HTH

[Mac]

I spent the last couple of years on a Masters and my Opels (69 & 73) set idle. As an easy first couple of projects I have been extending the back decks per the Blitz tech tip Jan 1998 (I've got pictures if anyones interested)and changing the vent lines and fuel delivery lines. The 73 conforms to the literature with two vents on opposite diagonals and a tie into to the tank stem, but the 69 has a single line coming from near the stem and no tee off of the stem itself. I haven't traced down where this single line goes yet, but I was wondering if anyone else has a similar arrangement and if I will be okay just running this single line up to a charcoal canister (none exists now so I guess I'll put one in).

I just joined the club and was not sure whether I should tack this question onto the nearest similar thread or start a new one. If I did wrong please inform me of proper etiquette. Thanks.

Mac

[kwilford]

Originally Posted by Mac I haven't traced down where this single line goes yet, but I was wondering if anyone else has a similar arrangement and if I will be okay just running this single line up to a charcoal canister (none exists now so I guess I'll put one in).

I don't know for sure about the '69, but the '71 and later has two connections to the tank (one at the top of the tank body, the other at the fuel filler neck), but they tee together under the back deck into a single line, which in turn connects to the cannister. If your '69 only has one connection, then that goes to the cannister. But make sure the cannister has at least one other connection that allows it to be vented (either into the air filter throat, or at least into the atmosphere) so the tank doesn't get pressurized

Originally Posted by Mac I just joined the club and was not sure whether I should tack this question onto the nearest similar thread or start a new one. If I did wrong please inform me of proper etiquette.

By all means, continue on with existing threads. The BEST thread is one that totally deals with the issue, and saves all kind of searching. In a perfect world, I would sort through all the threads, delete all the non-helpful posts, and merge the threads together that are related. But that would eliminate a lot of cheerful banter, and I would be doing NOTHING but moderating!

[oldroadiedog]

So I found the original cannister (I had taken it off myself and stashed it). As per Kwilford's advice I ran new vaccum hose from the vent line on the tank, along side the fuel line under the chassis and into the cannister. Because I've got a repositioned battery box, I had to mount the cannister in a sort of odd position after painting it. I then ran two hoses to the appropriate ports on the Weber 38 which oddly enough had both the valve throat and bowl vents. As far as fumes...I didn't detect any today on a test drive but with the cooler weather...well we'll see come warmer weather. I'm glad I utilized those vents- not having hoses on them could have created problems later.

[kwilford]

Originally Posted by oldroadiedog I then ran two hoses to the appropriate ports on the Weber 38 which oddly enough had both the valve throat and bowl vents.

Glad to have another satisfied customer!

Hey, I see the bowl vent connection on the Weber. Where did you find a "valve throat" connection to vent the cannister into? Can you take another photo? I am curious, because I have six (6; yea I know, so many carbs, so little time!) Webers in my garage, and only one had the bowl vent (A California-spec DGAV) and I installed one on my 38 DPS100 (a 38 DGEV look-alike), but none of them have a throat connection (that I could see). Maybe there is one here to be tapped into...

[oldroadiedog]

You can see the connection in the Carb JPG if you enlarge the image. There's a 90 degree flexible hose connector just below the vent for the vacum advance. I'll try and get a closer photo tomorrow.