Gas Cap Vented or Not Vented??

[Mr.FT]

On my 72 Demon how do I tell if the gas cap is vented or not??

Tom

 

[67Dart273]

The cap on a 72 is not actually, nor is it meant to be "vented" in the usual sense

Up until the first "carbon canister" evaporative emmissions came out, caps were NOT vented, and the tank vent was a 1/4" tube welded into near the top of the filler neck, went up to the top of the inner rear quarter, then doubled down along the filler, through the floor, and "open ended" in the rear frame rail.

The "carbon can" systems use what is called a "pressure vacuum" cap which lets air in at so much vacuum, and fuel/ air pressure OUT at so much pressure. They are meant as a relief, NOT an operational vent.

The "vent" on these is the "rest of" the carbon can system. If yours has been hacked up or removed you may not have a vent

See this thread:

http://www.forabodiesonly.com/mopar/showthread.php?t=183956

It's all described in the shop manual, and lucky you, since you have a 72, we have one here you can download for free:

the thread:

http://www.forabodiesonly.com/mopar/showthread.php?t=132309

the link:

[ame="http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf"]http://www.abodyjoe.com/pictures/Misc.%20car%20info/1972%20Plymouth%20Chassis%20Serv%20Man.pdf[/ame]

 

[Mr.FT]

Thanks for the info I'll have to start tracing lines to see what I have.