How do I stop vapor lock?

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Venting varies significantly by model and year from 69~70's. If you have a vent on your filler neck and at the sender, one or the other should probably be open. My '72 has a vent line from the tank up to the engine compartment that's attached to the top of the tank.

So long as it's filtered, and possibly even a roll-over valve, having one of them vented is likely a good idea so long as it vents somewhere other than into the trunk! It should go outside to the atmosphere. It should also be above the top of the fuel tank..
 
I tried WOT again, but not with the open gas cap. It sputtered a little, but I hadn't been driving it 100 miles either. It is apparently the vapor in the lines building up in heat, no doubt.

The thing that concerns me about opening the vent in the filler tube near the top of the neck is when filling the tank. The pumps sometimes do not shut off and the gas comes spilling out the lip of the filler tube. I didn't check to see if the vent tube is higher than the lip or not. Does anyone know if gas comes out that vent hole when filling if the pump doesn't shut off? I don't want gas in my trunk...

I plan on getting the vented filter and hooking it up to the vent tube on the sending unit in the next few days. I have a 400 mile trip to make, in my daily driver, so that is going to wipe me out for a few days, but then I will get to working on the vent lines and stuff.

I also plan on putting a heat shield tube around the fuel line and the vent line that goes near the headers. If "all that" doesn't fix it... I will get the electric fuel pump too. I gotta put the vent line, open the filler neck vent, and put the heat shield anyway even if I need an electric fuel pump, but if I can get away without the electric pump, I would rather.

Thanks for all the help!
 
Phreakish said:
Venting varies significantly by model and year from 69~70's. If you have a vent on your filler neck and at the sender, one or the other should probably be open. My '72 has a vent line from the tank up to the engine compartment that's attached to the top of the tank.

So long as it's filtered, and possibly even a roll-over valve, having one of them vented is likely a good idea so long as it vents somewhere other than into the trunk! It should go outside to the atmosphere. It should also be above the top of the fuel tank..
Click to expand...

I didn't see this reply till just now. I go to my statistics, look for my last post, then go from there. It was on page 2, this post was on page 3.

Anyhoo, I would like to open the vent at the filler tube and run the vent at the sending unit to the fuel filter shown earlier in the thread. But then I will have a vent into the trunk. Why would Chrysler put a vent tube into the trunk without there being a way to vent it to the outside?? Seems like there should be a way to get that to vent into the environment instead of into the trunk. Spill over seems like a real threat.

I figured out how to run the vent line from the tank to the fuel filter at the front. I can drill and attach clips to the same frame rail the fuel line is on. But what do I do with this crazy vent at the filler tube top?
 
70DusterBob said:
.......The thing that concerns me about opening the vent in the filler tube near the top of the neck is when filling the tank.!
Click to expand...

70DusterBob said:
......... I would like to open the vent at the filler tube and run the vent at the sending unit to the fuel filter shown earlier in the thread. But then I will have a vent into the trunk.
Click to expand...

Chrysler NEVER did and you MUST not vent into the trunk. Further, having, not having the early vent will have nothing to do with how the tank fills


PLEASE PLEASE do yourself a huge favor. Go over to MyMopar

http://www.mymopar.com/index.php?pid=31

and download SEVERAL factory shop manuals. 69 for certain, because it shows the early vent. 70--through 73, and read the fuel sections about "tanks" and the emissions sections about the evap / fuel system.



I posted this earlier and evidently you didn't see it or didn't read it. This is a good rendition of the non CA / early 70 and earlier vent. It comes out near the top of the filler, hooks to a tube, and bends UP near the top of the rear quarter, then down alongside the filler and OUT THROUGH the floor gasket and the tube ends "open" in the rear frame rail. IT IS NOT open to the trunk



2cmugso.jpg
 
What he just said ^^^

Take a look at the original diagrams.

What I would do if I were you is the following:
Vent from the filler through the filler tube grommet under the trunk (this way it doesn't vent into trunk).
Then run your return (either from a vented filter or a regulator) back to the vent that's currently capped at the sending unit.

Connecting the vent on the sending unit to the vent on the neck won't do anything ;)
 
67Dart273 said:
Chrysler NEVER did and you MUST not vent into the trunk. Further, having, not having the early vent will have nothing to do with how the tank fills


PLEASE PLEASE do yourself a huge favor. Go over to MyMopar

http://www.mymopar.com/index.php?pid=31

and download SEVERAL factory shop manuals. 69 for certain, because it shows the early vent. 70--through 73, and read the fuel sections about "tanks" and the emissions sections about the evap / fuel system.



I posted this earlier and evidently you didn't see it or didn't read it. This is a good rendition of the non CA / early 70 and earlier vent. It comes out near the top of the filler, hooks to a tube, and bends UP near the top of the rear quarter, then down alongside the filler and OUT THROUGH the floor gasket and the tube ends "open" in the rear frame rail. IT IS NOT open to the trunk



2cmugso.jpg
Click to expand...
I had very same issues.
I listened to 67Dart and put the sleeve heat shield on my fuel line from where it enters the engine compartment to the pump, from the pump to the regulator, and from the regulator to the carb.
Installed 1" phenolic carb spacer.
Changed out my dead head regulator for a return style and ran the return to the old tank evap line.
Installed a vent just as in the diagram through the grommet down into the frame rail area.
Have not had another problem since.
Using a Holley Mechanical pump and a Holley regulator set to 5.5 psi with my Eddy carb.
Listen to him. :prayer:
Knows his $H!T :cheers:
 
Thanks,

I will go read up on the manual. I am not sure if there is something that goes between the vent tube connected to the filler tube and the vent tube assembly. Is the vent tube assembly a functioning part that has some sort of valve in it? Like a one way or something? Or is there some sort of functioning part between the vent tube connected to the filler tube and the vent tube assembly?

I will go look at the manual. If it is a PDF I will save it for future reference.

Thanks again,
I just hope this problem isn't due to a clogged sock on the end of the sending unit tube. I had a crapped out fuel filter that had only been on there "Maybe" 1000 miles, if that, and I have gone about 800 or more with the clear filter and haven't had one spec of anything in it yet. Very suspicious.
 
That site has a TON of manuals in it! Thank you so much for the link. I am downloading them now...

If I had that totally clogged crapped out fuel filter with black crap in it, and am getting nothing in the clear one now with just as many if not more miles on it than the crapped out one, what do you think the chances are that the sock is clogged? I hate to drop the tank. I have all my gas cans full from siphoning out the bad gas that was in it, it was maybe 6 mo old, but it was giving me poor performance. I guess I will have to take the bad gas to the toxic dump and empty them out... Man... What a mess! :banghead:
 
70DusterBob said:
That site has a TON of manuals in it! Thank you so much for the link. I am downloading them now...

If I had that totally clogged crapped out fuel filter with black crap in it, and am getting nothing in the clear one now with just as many if not more miles on it than the crapped out one, what do you think the chances are that the sock is clogged? I hate to drop the tank. I have all my gas cans full from siphoning out the bad gas that was in it, it was maybe 6 mo old, but it was giving me poor performance. I guess I will have to take the bad gas to the toxic dump and empty them out... Man... What a mess! :banghead:
Click to expand...

What sock? :D
You mean the one you found bits of in the fuel filter?
That would explain the dirty filter thing wouldn't it?
 
70DusterBob said:
Thanks, I am not sure if there is something that goes between the vent tube connected to the filler tube and the vent tube assembly. Is the vent tube assembly a functioning part that has some sort of valve in it? Like a one way or something?
Click to expand...

Not sure if you are referring to the earlier 69 type vent or the newer "up front" which interconnects with the carbon can system

The old system has no valve. The cap is completely sealed, and the vent is simply an open 1/4" tube that goes down and ends, open end, inside the rear frame rail. The only possible way it could dribble is if the tank is EXTREMELY full, "up into" the filler tube, and either expands enough, or is parked on a side hill so that fuel is forced out. Even so, only a cup or two will drain, after it gets down below that level it can no longer do so.

If you are referring to the 70/ later evap system, "it changes." Your car should have a vapor separator can in the trunk. The 1/4 line up to front has a valve right near the engine end. If you look through those manuals, it's in there. Again, some is in the fuel system, and some is in the emissions section in the back of the book
 
L0L!

No, someone called the pick up screen in the tank a sock I think. I call it the pick up screen. But if my filter was "that" plugged up with crud, I figure maybe the pick up screen is full of crud too. That would explain why it is running out of fuel on WOT after the bowls run dry which is the only problem I am having now.

I just gotta buy "another" 5 gal gas can to drain what is in the tank so I can drop the tank and check the "sock" or pick up screen. I checked and in my area I have to make an appt for the hazardous waste dept to come pick up my old gas. I don't have time to wait. (BTW...If you ever have old gas to get rid of, google, "Where to dispose of gasoline in ____________" fill in the blank with your area.)

I checked the manuals and it doesn't say if there is a functioning part between the filler tube vent and the exit to atmosphere under the car. Does anyone know the safest place to place the tube where the fumes will be exiting into the atmosphere? I'm thinkin' close to the middle of the car right by the sending unit, but lower than the gas tank to keep it away from backfires coming out the exhaust should I ever have a backfire.

Is there a functioning part between the filler tube vent and the exit to atmosphere?

I now know how to hook-up the vent tubes. They are all wrong on my Duster right now.
 
67Dart273 said:
Not sure if you are referring to the earlier 69 type vent or the newer "up front" which interconnects with the carbon can system

The old system has no valve. The cap is completely sealed, and the vent is simply an open 1/4" tube that goes down and ends, open end, inside the rear frame rail. The only possible way it could dribble is if the tank is EXTREMELY full, "up into" the filler tube, and either expands enough, or is parked on a side hill so that fuel is forced out. Even so, only a cup or two will drain, after it gets down below that level it can no longer do so.

If you look through those manuals, it's in there. Again, some is in the fuel system, and some is in the emissions section in the back of the book
Click to expand...

I looked through the fuel tank section of the manual from 69. I do have the 69 style. It did say to vent into atmosphere. I'm just thinkin' it would be safer to place the exit of the vent tube in the center of the car near the front of the fuel tank, but lower than the fuel tank, between the fuel tank and the rear-end, so that it is as far as possible from any backfires. My exhaust exits right behind the back wheels, I mean right behind the back wheels, so if it were to come out the grommet and exit into the frame rail, it would be extremely close to my exhaust. It is dual.
 
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