Overfill limiting valve

-
Yote

Yote

Well-Known Member
Joined
Aug 30, 2015
Messages
1,404
Reaction score
730
Location
far eastern Colorado
re: 72 demon
Replaced vapor line and noticed that it does not have what I believe to be the overfill limiting valve near the top of line in the engine bay. My old line had a valve built into the line. Is this important to have and why ? If so , is there an add on valve available.
Yote
 
If you have everything connected "as per original" I would think SO. After all, Ma just didn't throw parts in there without reason, and if "she" could save two cents, it would have been left out

The thing you have to be careful of, is that the vapor control system saw changes almost every single year. Reading through the shop manuals from 70--76 or so will show up "some" of the differences
 
I tried to figure this out when I did mine. I seems nobody makes one and most people either leave it out or never knew it was there. So apparently it is not essential. I cut mine off the old line flushed it out with carb cleaner and pushed it up in the hose before attaching to the vent line.. just need to be sure it stays vertical.
 
According to Chilton's...
"The limiting valve prevents the fuel tank from being overfilled by trapping fuel in the filler when the tank is full. When pressure in the tank becomes greater than the valve operating pressure, the valve opens and allows the gasoline vapors to flow into the charcoal canister."
I thought there was more about it in the service manual, but cant seem to find it at the moment.
 
See page 25-15 of the '72 Plymouth Chassis manual which you can download, free from MyMopar. That manual, as well as several others "over there" came from the guys here at FABO. That one thanks to AbodyJoe

valve1.jpg


valve.jpg


If you are unfamiliar with what they are calling "inches of water pressure" this is exactly what it says........measured in inches of rise in a column of water, otherwise known as a manometer

manometer-intro1_pic.gif
 
Last edited:
Thanks Del. Have the 72 Dodge manuals but haven't run onto that. Guess I better look better. Have tried in past to sign in and access MyMopar and couldn't get it done. And some members think this new site is difficult.
Yote
Any suggestions for a limiting valve ? It would appear that without it raw fuel could be drawn into the vapor canister. Correct me if I'm wrong.
 
This is a super old thread but I am researching the components of my '72s fuel and NOx systems. Reading up on the fuel system in the factory service manual, I see this valve and as others have stated, there really isn't anything out there to replace the factory "overfill limiting valve".

Screen Shot 2023-02-07 at 10.46.27 AM.png


However, I have found this after hours of googling and searching. Seems like it would work?

Screen Shot 2023-02-07 at 10.51.13 AM.png


I'd just need to install towards the top of the vent line near the vapor canister and adapt the size from 1/4" to 5/8" and back. Still searching and hoping to find one with 1/4" input/output. Some might say to just leave it off the system but it does serve an important purpose. Thoughts @67Dart273
 
You must log in or register to reply here.
-

Back
Top