Fuel Tank Vent Valve?

I think my oem locking gas cap, that was with my 71, is a non vent. Though it has some odd plastic thing that may be a pressure valve.

Here a link to my post, to check your locking gas cap with what is pictured.

Mine has an AMC part number that is hidden by the thick rubber seal. I removed it to show in one of the pictures.

http://theamcforum.com/forum/oem-locking-gas-cap_topic87884.html?KW=Locking+cap

Cameron....what you are describing is what the Parts Book calls "WCFE"...additionally Mike is correct to.  The valve is a roll over valve, it is connected to a plastic tank within your fuel tank....which decreases the amount of fuel you tank holds.  Additionally, as Mike has said it was introduced in 1970, carried over 71 up.  The WCFE stands for With California Fuel Emissions, which includes the vapor tank in the main fuel tank, roll over valve and tubing that runs from the roll over valve to the rear of the valve cover (1970 only), then in 1971 the Charcoal Canister was introduced which changed the location of the termination point of the line from the tank.  Having the engine vacuum (direct) was a really poor way of containing the vapor and was only done for 1 model year.   The Tank Venting via Charcoal Canister continued in several ways from 1971 up.

Edited by 401MATCOUPE - Jun/28/2017 at 6:33am

Mopar_guy....this is a great example of how almost every year AMC changed the "Emissions" systems, to keep up or ahead of Federal Mandates.  The WCFE systems as I mentioned before were either not documented or very poorly documented in the TSM's.  The Part Catalog is very accurate in the part numbers but can also let you down with poor Illustrations and Diagrams.  1970 is the most confusing since there are actually 3 different part numbers for the Fuel Tank in the Javelin and AMX (Series 30 and 70).  I have never found a break in point or Line Number break in, this has caused much confusion over the years for which gas cap to use...Vented or Non-Vented.....wrong cap/tank combination will cause the fuel system to suck the bottom of the tank up and create a vacuum in the tank from fuel being pulled by the fuel pump and no vent to keep it flowing.  A great example of the changes to the Charcoal canister is in 1971, the unit had only 2 or 3 nipples (Model and Engine dependent), later canisters had up to 6 nipples for vapor containment.

Edited by 401MATCOUPE - Jun/28/2017 at 6:54am

304-dude wrote: I think my oem locking gas cap, that was with my 71, is a non vent. Though it has some odd plastic thing that may be a pressure valve. Here a link to my post, to check your locking gas cap with what is pictured. Mine has an AMC part number that is hidden by the thick rubber seal. I removed it to show in one of the pictures. http://theamcforum.com/forum/oem-locking-gas-cap_topic87884.html?KW=Locking+cap

Edited by CamJam - Jun/28/2017 at 11:59am

You're welcome. Glad I could help. Yes Ross, the emission requirements were changing every year or so back then. I knew what the valve was since I have one but the TSM pages explained it better than I could. That diagram page is really good. When I move my tank location, I'm actually going to put a charcoal canister back in the car because I'm tired of smelling the fumes.