Flip fuel cap on Duster need to be vented?

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Wvbuzzmaster

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Just bought a flip top gas cap to put on my 1972 Duster. I bought a delrin adapter, and installing it is not the question, but rather function. The current standard cap on my a Duster is clearly vented, and my new to me flip top gas cap is not vented (smooth version, not the version marked “FUEL”). If I install a non vented flip top gas cap on my Duster will I be creating a new problem because it’s not vented?
 
What year Duster? The tank may already have a vent. The gas cap may or may not be stock.
Pictures by chance? Sounds like a cool conversion you did.
 
The inside of the filler neck appears to be vent integrated?? Not sure if cap should be though... in 1972... to complement that? Or am I imagining things?
 
Here is the deal. 70/71 and maybe? early 72 did not all have evap controls. NO MOPAR CAP is supposed to be vented. The vent is suposed to be provided in the tank system. If you do NOT have evap emissions, look in the 69 shop manual (download them from MyMoar) to see how the simple vent works, and you can identify it. If there is a 1/4" tube welded into the filler neck, running down through the trunk floor you have a non-evap system

If you have or have had an evap system, there is a 1/4" line running up front into the engine bay interconnected with the evap controls. This line MUST be open, even if the evap stuff is removed because that IS the tank vent

If you run a vented cap you run the risk (with a full tank) of running fuel down the fender

Link to MyMopar service manuals. You may have to take a Dodge / vs a Plymouth or vice versa

Service Manuals – MyMopar
 
Well then... I do believe I have some revisions to make in my fuel system....

I have the 1/4” line on the passenger inner fender under the hood and believed it was a fuel return line and plumbed it as such with a fuel filter that has the third orificed nipple on it. I knew the evap thing was missing but hmmm... now what... I haven’t been running it long like that, only plumbed it that way in November and drove the car 20 miles randomly before decommissioning it for safety rework...

My fuel sender has an extra nipple on it that has a hose and and bolt plugging it off currently... could use that for return and remake a vent hose out back somewhere... or add a vent hose in filler neck, or ... someone smarter than me can just tell me how many dollars to make it right and I put it right???
 
The other thing you could do if you are "handy" is modify your filler neck AKA weld a fitting into it and remake the old style vent 69/ earlier

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One complication to "not fall into" is that it seems most? all? the vented fillers install from the inside of the trunk, and the cars with no filler neck vent install from the outside of the trunk
 
I did notice that difference in the filler neck on my 1972 Duster versus my Dad’s 1966 Dart. Had a thought on a work around being that I could weld a pipe thread bung into the filler neck on the 1972 Duster that is flush on the outside of the tube and then thread a hose barb fitting in with thread sealant after it’s back in the car.
 
I'm thinking of the exact thing. I have a 74 Scamp in "body shop hell" right now
 
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