1972 Challenger Charcoal Canister Workaround

[ghjedi]

I'm replacing the original gas tank on my 72 Challenger.  I know that my car had the charcoal fuel vapor canister upfront near the radiator as part of its emissions system, but it was removed long ago.  I know the canisters are hard to come by now and from what I've read here, they are not really needed.  I'm not so interested in correctness, as I am functionality (i.e. reducing raw fuel vapor smell).

Here are my questions:

1. For the fuel line coming off the gas tank that goes to the charcoal canister, if I simply cap it off, will that be okay?
2. If so, how long should this fuel line run before capping it off?

I read on a few older threads that some had capped off this fuel line or put a filter on the end, so I would appreciate any insights on what others have done.

[femtnmax]

I went thru the same questions on my 74.   If I remember right, 1970 had a gas tank vent line that went to a higher location than the top of the tank, then dropped down below the bottom of the tank, and inside the frame rail just forward of the rear axle.  I routed mine that way. 
I was able to route up against the bottom side of the trunk floor, just forward of the rear shock mount cross piece, thus higher than the gas tank.  Then routed along the inside of the frame rail, following the frame rail all the way down to where the rail bends and points forward.  At that point, the lower frame rail on my 74 had a hole in the side of the rail, also holes in the bottom of the rail.  I routed the vent line in thru the side hole.  I had installed boxed tubing subframe connectors and ran the vent line forward the entire length of the oem frame rail, then into the box tubing.
Some said to install a small fuel filter on the end of the vent line.  I have not done this yet, but would probably be a good idea.
I would not cap off the vent line.  The original idea was to send all the gas tank vapors to the canister, then into the engine.  Capping it off does not give the vapors anyplace to go.

[dodj]

If you simply cap the vent line, it will pressurize. Not a good idea unless you buy a vented gas cap. I ran mine out the passenger side to the outside of the frame rail behind the tire and put a small fuel filter on it. I figured it may prevent dust getting back into the tank.

[Barracudadan]

I have been keeping an eye on this thread since I have the same issue.My vent line ends in the engine bay and I no longer have the charcoal cannister just the bracket. I put in a new gas tank but have yet to put a drop of gas in the tank. What is the worst thing that could happen if I just leave my line alone it`s open like it should be can it leak any gas or is a gasoline smell all I have to worry about? Does just putting a small fuel filter on the end of the line help get rid of any gas smell?

Where do the cannister lines connect to anyway?I know one line is the vent from the gas tank what do the other two lines connect too I know they go towards the carb but not sure what they hook up to air cleaner or carb itself?If someone has pictures to show the connections that would be great.

[dodj]

I suppose fuel could get out but it goes through a vapour separator, so it is not supposed to get out that way. Filter does nothing for the vapour smell. I put mine where I described so if fuel did come out it would be in a relatively harmless area.

[Bullitt-]

Where do the cannister lines connect to anyway?I know one line is the vent from the gas tank what do the other two lines connect too I know they go towards the carb but not sure what they hook up to air cleaner or carb itself?If someone has pictures to show the connections that would be great.

72 only used the one little line.. 73-4 adds the big purge line., if you don't have an OE carb you probably have nothing to connect to.


I have had the idea to use a one way valve for a tank vent, such as the one man brake bleeder I have, cost less than $5.00

 

[dodj]

Nice clean afb Bullitt, one of your rebuilds?

[Bullitt-]

Nice clean afb Bullitt, one of your rebuilds?

Not mine....Thermoquad.....here's the one on my car

[dodj]

Nice! How did you get it so clean? Chemicals or elbow grease?

[Bullitt-]

Nice! How did you get it so clean? Chemicals or elbow grease?

a big soft wire wheel on a bench arbor after soaking in a vinegar solution

[ghjedi]

Not mine....Thermoquad.....here's the one on my car

That is a beauty!

[ghjedi]

72 only used the one little line.. 73-4 adds the big purge line., if you don't have an OE carb you probably have nothing to connect to.


I have had the idea to use a one way valve for a tank vent, such as the one man brake bleeder I have, cost less than $5.00

 

The one way value is a great idea!  Until I get my hands on one, I'll go with routing the tube to a harmless location, should fuel come out.

[ghjedi]

I went thru the same questions on my 74.   If I remember right, 1970 had a gas tank vent line that went to a higher location than the top of the tank, then dropped down below the bottom of the tank, and inside the frame rail just forward of the rear axle.  I routed mine that way. 
I was able to route up against the bottom side of the trunk floor, just forward of the rear shock mount cross piece, thus higher than the gas tank.  Then routed along the inside of the frame rail, following the frame rail all the way down to where the rail bends and points forward.  At that point, the lower frame rail on my 74 had a hole in the side of the rail, also holes in the bottom of the rail.  I routed the vent line in thru the side hole.  I had installed boxed tubing subframe connectors and ran the vent line forward the entire length of the oem frame rail, then into the box tubing.
Some said to install a small fuel filter on the end of the vent line.  I have not done this yet, but would probably be a good idea.
I would not cap off the vent line.  The original idea was to send all the gas tank vapors to the canister, then into the engine.  Capping it off does not give the vapors anyplace to go.

Thanks for the insight.  My old tank is off now and in addition to being rusty, I just found out that it had a screw punched through it that the previous owner must have done while putting in the trunk lining.  Not good.  I think that explains a lot of the raw fuel smell I was getting, especially after filling the tank.

[femtnmax]

I just found out that it had a screw punched through it that the previous owner must have done while putting in the trunk lining.  Not good.  I think that explains a lot of the raw fuel smell I was getting, especially after filling the tank.

That's real good you found that 

[dodj]

That's real good you found that 

No kidding! Especially if you are a smoker and had one going while getting something out of the trunk!