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73RR fuel tank vent hose siphoning gas

manic_mopar

manic_mopar

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So just recently, i noticed a fuel leak back near the tank, just in front. It would spurt out a little gas and then stop. I finally figured out it was coming out of my vent tube from the top of the tank! We do not have any factory vent lines anymore, just a fuel-safe rubber hose that lets it breathe.

What would typically cause fuel to be pushed out of the top of the tank and through the vent hose? Nothing has changed to the fuel system, and this has happened at low fuel levels as well as a full tank.

Thanks!
 
Hmmm, you didn't say what year and I assume a B body. On the 68-70 cars, if the car is on level ground this doesn't make sense that it's leaking with a partial tank. There is nothing to "push" it up and out. If it's on an incline it might make more sense because the short line in the tank attaches to the long line that goes into the trunk for just that reason, the long vent tube prevents fuel from coming out, the opposite is true of the factory long line in the tank, it attaches to the short line that attaches by the shock tower so......the only way I can see the car leaking on level ground from a vent tube is that maybe one of the other is stopped up causing pressure in the tank but that's a real stretch with a partial tank. I would double check to make sure it's from the vents and not the tank itself. If you are certain that's where it's coming from then reinstall the correct tubes and see if that cures it. They are easy to install and ss tube has them
https://www.ebay.com/itm/68-70-Dodge-Plymouth-B-Body-Except-Charger-Trunk-Mounted-Fuel-Tank-Vent-Kit/251223156600?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 
On a 73 tank you should have a vent at each corner, that all come out at the top front of the tank- IE four nipples.

These are supposed to connect, via four short hoses, to a manifold/two way check valve.

You say there's no vent any more...how do the lines now run from the four vent nipples?
 
Bill Monk said:
Hmmm, you didn't say what year and I assume a B body. On the 68-70 cars, if the car is on level ground this doesn't make sense that it's leaking with a partial tank. There is nothing to "push" it up and out. If it's on an incline it might make more sense because the short line in the tank attaches to the long line that goes into the trunk for just that reason, the long vent tube prevents fuel from coming out, the opposite is true of the factory long line in the tank, it attaches to the short line that attaches by the shock tower so......the only way I can see the car leaking on level ground from a vent tube is that maybe one of the other is stopped up causing pressure in the tank but that's a real stretch with a partial tank. I would double check to make sure it's from the vents and not the tank itself. If you are certain that's where it's coming from then reinstall the correct tubes and see if that cures it. They are easy to install and ss tube has them
https://www.ebay.com/itm/68-70-Dodge-Plymouth-B-Body-Except-Charger-Trunk-Mounted-Fuel-Tank-Vent-Kit/251223156600?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
Click to expand...
my bad, I just saw 73
 
Thanks for the responses. I actually am not 100% sure how it's laid out up there. It was setup like this by the previous owner, never had an issue, so never looked at it up close yet. I know we have 1 vent hose looped up from those forward 4 vent holes, and hangs down to the axle. I'll get under there today and snap some pictures and post them up.

Does someone make a full vent tube/manifold setup for the 73/74 bodies like that one you posted bill? I'm not against getting that properly setup again!
 
After the vents are combined in the manifold, the now single vent line goes up to the charcoal can on the pass side inner fender.

A valve (actually two) on the accelerator pump opens a connection from the can to the fuel bowl, allowing the vapors to enter and then burn with the incoming fuel. The second valve IIRC opens at cruise if the temp is hot enough via a fitting on the intake.

The two way valve in the manifold keeps gas from going up the vent, and keeps pressure from entering the tank in the event of a malfunction at the other end.

That valve stuck in mine and caused the tank to build so much pressure it leaked through the pinch weld, and would blow the gas cap out of my hand when I removed it!

I had to cut a hole in the manifold, and carefully drill out the nipple to remove the brass shuttle. Then I had to weld back in the piece I cut out and coat the are with JB weld.

That solved the problem.

My charcoal canister is not installed, but the vent from the tank does go to the accelerator pump valve.
 
Here is the factory vapor separator for 73 RR.
IMAG1693.jpg
 
FYI, if you are using a stock tank, the 4 lines for vapor run across the top of the tank to each corner of the tank.
 
manic_mopar said:
Thanks for the responses. I actually am not 100% sure how it's laid out up there. It was setup like this by the previous owner, never had an issue, so never looked at it up close yet. I know we have 1 vent hose looped up from those forward 4 vent holes, and hangs down to the axle. I'll get under there today and snap some pictures and post them up.

Does someone make a full vent tube/manifold setup for the 73/74 bodies like that one you posted bill? I'm not against getting that properly setup again!
Click to expand...
Not that I'm aware of but I'm sure it's 1/4" line, you should be able to bend your own easily
 
Well i definitely found the problem. Just needed yall to get me under the car and look for myself. I also just noticed how ridiculous my fuel line is. I never knew it had a rubber piece in the middle of the line like that.

Are reproduction manifolds year specific or can i get something for another car that would work for mine?

Also, idrivemopar, the underside of your car looks nicer than the topside of my car. amazingly beautiful. lol

fuel tank.jpg
 
I would really love to replace that old tank. The previous owner/idiot capped the sending unit and just drilled and tapped the bottom front of the fuel tank and is feeding the engine from underneath now. Definitely a hazard and it looks terrible. Which company did you go with pwermyster?
 
I got it off rockauto. Can’t remember which one I got. Think the list spectra and dorman. It was made in Canada if that helps. I can dig out the invoice later

Actually only had the car out for the first time this weekend and just over half filled it to make sure it all sealed well. Have to get back under it and check
 
No worries, I was mostly just curious. There are so many brands out there. Thanks for the pics!
 
manic_mopar said:
Well i definitely found the problem. Just needed yall to get me under the car and look for myself. I also just noticed how ridiculous my fuel line is. I never knew it had a rubber piece in the middle of the line like that.

Are reproduction manifolds year specific or can i get something for another car that would work for mine?

Also, idrivemopar, the underside of your car looks nicer than the topside of my car. amazingly beautiful. lol

View attachment 590511
Click to expand...
Yeah, get the correct tank, that's a good start, I am using a spectra premium. I don't know where you will be able to get a new vapor separator, I de-rusted my original and then painted it, but not 100% sure the internal valve still works 100% but I haven't had any issues with it.
 
I have a Spectra (made in Canada) as well.

Note the sender clamp rings are thin and crappy. Find an OEM one if you can.

Separator manifold is almost impossible to find.

I was all set to make one out of brass fittings, but brass has gone up and total was over $40!
 
I’ll second that about the ring, I got one with new tank and one with sender, both garbage. The original ring was much tighter
 
powermyster said:
I’ll second that about the ring, I got one with new tank and one with sender, both garbage. The original ring was much tighter
Click to expand...
If ur not running the vapor canister, and all that junk, why not just tie the vent lines together, and run them up in the trunk, out of the way , put t a couple of coils in the top and run it back down thru the trunk floor. I ran the front center vent line on mine like that and haven`t had a spill over or any problems out of it. I still have the orig vent that ties into the filler neck on it too, but it runs down and back a little to the rear, strapped to the frame. It hasn`t overflowed either.
 
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