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Thread: Gas tank vent

  1. #1

    Default Gas tank vent

    The car is a 79 302 that has no charcoal canister or any sort of emission gear. Edelbrock carb.
    When I dropped my gas tank it had nothing attached to the tank vent. I added a clear plastic hose and ran it up by the filler neck. Well that's not doing anything good as even with just 6 or 7 gallons in the tank its burping gas and gas stays in the tube Where should this be run to and how?
    I assume it would be up in the fender somewhere with a roll over valve.

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    Last edited by brian.aughe; 04-01-2020 at 01:21 AM.

  2. #2
    FEP Super Member xctasy's Avatar
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    JA Cook noted this on the tank requirements .


    See http://vb.foureyedpride.com/showthre...Fuel-tank-vent


    Quote Originally Posted by JACook View Post
    You don't need any wiring if you're just hooking up the evaporative system to the fuel tank. And if you
    no longer have the stock carburetor, that's your only choice anyway. The only electrical connections on
    the original system were for the carburetor bowl vent solenoids. Otherwise, the entire system runs off
    vacuum.

    Apart from the lines that went to the stock fuel bowls, the system needs only to connect to the fuel tank
    vent line, and also a pair of vacuum lines for canister purge. One goes from the purge valve to manifold
    vacuum, and the other is a control line that originally went to EGR vacuum, but can work just as well off
    the ported vacuum source for the distributor.

    This thread should have all the info you need to get a canister purge system working-
    http://vb.foureyedpride.com/showthread.php?t=71264

    And this post in that same thread has the Cliff's Notes photo of what the purge valve looks like, and
    what needs to connect where- http://vb.foureyedpride.com/showpost...4&postcount=37

    Your car originally would have had a much more complicated evaporative system than you probably need
    now. Originally it would have had one canister on the engine bay side of the right frame rail, and a second
    canister on the fender side. I don't have a good photo of the mounting bracket, but if you look at the back
    side of a canister, you'll see the wedge shaped area that engages the bracket, so you know what to look for.

  3. #3

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    Quote Originally Posted by xctasy View Post
    JA Cook noted this on the tank requirements .


    See http://vb.foureyedpride.com/showthre...Fuel-tank-vent
    Well looks like I'll be trying to find some sort of canister setup.

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  4. #4
    FEP Super Member xctasy's Avatar
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    yeah, that is my suggestion. 4 or 6 cylinder 1981 vapor tanks are around if you ask for them. Make sure you put Pennsylvania on your whereabouts.

  5. #5

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    Looks like LMR has a few options for a canister. I just have to figure out how to route it and where to mount it.

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  6. #6

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    I assume the bigger of the two inlets is the line to the fuel tank. The smaller is a vacuum line to where???

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    Last edited by brian.aughe; 04-01-2020 at 04:06 AM.

  7. #7
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by brian.aughe View Post
    I assume the bigger of the two inlets is the line to the fuel tank. The smaller is a vacuum line to where???

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    Thats the 1983-1985 4 bbl carb Mustang canistor, not what you need.

    Quote Originally Posted by TWR2003 View Post
    OK,
    Just FYI here are some pics of the 1978 and 1990 canisters that I have. The 1978 one (on the right with the single blue cap) is the original one from my car. Its missing the fitting that went on the port that has no cap. I have some old snapshots of it when the car still had the I-6. The missing cap had 4 hose fittings on it and I think it also had a vacuum contolled valve built into it. It would have looked like this:


    The other (blue) cap is original.

    The other canister has two part numbers on it:
    E2ZE-90653-CA
    F0ZE-9C985-AA

    It also appears to have a date code: 921012 which I assume to be either Oct 12 1992 or Dec 10 1992. I thought it had come from a 5.0L Mustang however it has only one hose nipple molded in. If you look closely (last pic) it looks like the other hose nipple is just a plug but its not - its molded over.

    In the very front of the pics are some fittings that will fit if you remove the mushroom caps. I must have grabbed them when I got the later canister (thinking Id need them) but now that I know I need the canister with the two hose nipples molded I guess I do not need these fittings. Im not sure what applications used them.

    Even though I do not need to meet emmisions requirements in my state to to the age of my vehicle (1978 ) I intend to correctly install all of the emmision control devices on my 5.0L just as they would be for a c. 1989-1990 5.0L Mustang.

    I hope this info helps.

    T


    Purge Valve tees of the small line. Large one is normally a capped opening to the activated carbon canister.


    Cale had one set up in his 1985 Mercury Capri post, JA Cooke got it set up for him. I was looking last night my time, but lost the internet at 2 am. If you click on http://vb.foureyedpride.com/showthre...vap-components


    That should help,





    Post #37 is the Purge Valve



    Post # 48 is the general single Carbon canister




    from post #46 used these additional parts.






    JA Cook's advice



    You can hook the manifold vacuum line from the purge valve to the tree on the
    back of the intake if you don't have the EGR spacer anymore. The brown delay
    valve goes in the line between your distributor vacuum source and the purge
    valve. You can just tee into the line to the distributor.

    The numbers on the delay valves are engineering numbers, and are not the best
    way to identify the valves. I've got two brown-sided valves with the same number
    molded into 'em, and they work exactly opposite each other. Fortunately, that's
    not so important for this project.

    What you want is the valve to be installed so that it resists applying vacuum
    to the purge valve, and easily releases the purge valve when vacuum goes away.
    Or to put it another way, the end you can blow through goes toward the purge
    valve.


    CFYI.




    From http://vb.foureyedpride.com/showthre...ister-plumbing

  8. #8
    FEP Super Member xctasy's Avatar
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    You can get a new "vented" gas cap., and block or plug the vapor valve seal That might help you out easily.

    I'd personally follow Cale's method, fit the Purge Valve, charcoal canister, and the two delay vales with the two prong connector to the charcoal canister.


    Charcoal canisters vary in position. My two hole 81 was hidden under the fender skirt.





    You could use a later E3 code 1983 model year three hole Charcoal canister if you capped the third small hole.

    You need some way to vent the tank. It does not have to be a carbon canister, but it does need a vent.

    With no vent, as gas is pumped out of the tank the volume above the fuel increases. That causes a vacuum to form which will tend to reduce the effectiveness of you fuel pump and can cause vapor lock. If you don't do anything else, either get a vented cap or drill a very small vent hole in your current fuel tank cap.

  9. #9

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    Here’s mine

    Name:  x7mPj1.jpg
Views: 156
Size:  201.0 KB

    from a 6 banger but maybe it will help?
    79 Zephyr, 4.6L 4v/4r70w swap, with team z front and rear suspension, 8.8 and upgraded brakes and coil overs. Running Holley Terminator X Max.

  10. #10

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    Well I'm gonna do some reading and see what I can do to make it simple. There was nothing on the tank for the 1000 miles or so I have driven it. After I installed the IRS I figured at a minimum I would add that line up to the filler neck.
    I'll talk to my local guy and see what his thoughts are. I guess he has done this a few times before where no canister at all is used.
    Every time I turn around with this car its something else. At least that list is getting smaller.

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  11. #11

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    Quote Originally Posted by xctasy View Post
    You can get a new "vented" gas cap., and block or plug the vapor valve seal That might help you out easily.

    I'd personally follow Cale's method, fit the Purge Valve, charcoal canister, and the two delay vales with the two prong connector to the charcoal canister.


    Charcoal canisters vary in position. My two hole 81 was hidden under the fender skirt.





    You could use a later E3 code 1983 model year three hole Charcoal canister if you capped the third small hole.

    You need some way to vent the tank. It does not have to be a carbon canister, but it does need a vent.

    With no vent, as gas is pumped out of the tank the volume above the fuel increases. That causes a vacuum to form which will tend to reduce the effectiveness of you fuel pump and can cause vapor lock. If you don't do anything else, either get a vented cap or drill a very small vent hole in your current fuel tank cap.
    Thanks for all your help.

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  12. #12
    FEP Super Member xctasy's Avatar
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    Quote Originally Posted by massacre View Post
    Here’s mine



    from a 6 banger but maybe it will help?

    There are a range of charcoal canisters. Some have four hoses, like this one.




    The general rule is. Do what you can afford first, and then try for something better if the situation allows.


    The I6 stuff is always a good first start because not that many Fox Mustangs were V8 OEM from factory.

  13. #13
    FEP Member 0F0 CBR's Avatar
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    I see this thread and project is very similar to what I am working on.
    The fuel tank vent hose on my car has been left open and tucked into the fender ever since I pulled the 4 cyl turbo 28 years ago.
    It always smelled of gas and and if I plugged the vent hose it would develop an air lock and the engine would quit after a few miles.
    To make matters worse, I unknowing bought a marine carb at the local swap meet and have been using it for the same time period.
    The main difference with marine carb is there are no vacuum ports or spark ports, as boats rarely idle and the are rpms are fairly constant.
    Left picture below.
    Name:  Carbs.JPG
Views: 295
Size:  70.2 KB
    The only port on it is above the choke plates at the very top - I've read it is to get plumbed to the fuel pump overflow on a boat to prevent spills.

    I am now putting in a charcoal canister and purge system, but do not have a spark port to plumb the to the purge valve pilot.
    The schematic below is the circuit I have come up with, I think in theory they work similar.

    Name:  Purge Circuit.JPG
Views: 298
Size:  45.0 KB

    The difference this will purge all of the time even at idle, when plumbed to the spark port, the purge valve only opens to purge the canister at part throttle.
    The temperature switch is to disable it when the engine is cold.
    I will let you know how it works after installed, i'm a little concerned about the constant vacuum leak at idle, might have to play with orifice sizes.

    Its amazing how we first spend all of our time and money making modifications, and later spend all of our time and money trying to put it back to original.
    Eventually I will get rid of this carb and put in an EFI Carb unit.

  14. #14

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    Quote Originally Posted by 0F0 CBR View Post
    I see this thread and project is very similar to what I am working on.
    The fuel tank vent hose on my car has been left open and tucked into the fender ever since I pulled the 4 cyl turbo 28 years ago.
    It always smelled of gas and and if I plugged the vent hose it would develop an air lock and the engine would quit after a few miles.
    To make matters worse, I unknowing bought a marine carb at the local swap meet and have been using it for the same time period.
    The main difference with marine carb is there are no vacuum ports or spark ports, as boats rarely idle and the are rpms are fairly constant.
    Left picture below.
    Name:  Carbs.JPG
Views: 295
Size:  70.2 KB
    The only port on it is above the choke plates at the very top - I've read it is to get plumbed to the fuel pump overflow on a boat to prevent spills.

    I am now putting in a charcoal canister and purge system, but do not have a spark port to plumb the to the purge valve pilot.
    The schematic below is the circuit I have come up with, I think in theory they work similar.

    Name:  Purge Circuit.JPG
Views: 298
Size:  45.0 KB

    The difference this will purge all of the time even at idle, when plumbed to the spark port, the purge valve only opens to purge the canister at part throttle.
    The temperature switch is to disable it when the engine is cold.
    I will let you know how it works after installed, i'm a little concerned about the constant vacuum leak at idle, might have to play with orifice sizes.

    Its amazing how we first spend all of our time and money making modifications, and later spend all of our time and money trying to put it back to original.
    Eventually I will get rid of this carb and put in an EFI Carb unit.
    The true curse of modding a car,, is demodding it so you can get back to enjoying it.
    Very interested to see how your project works out.

    Sent from my SM-G981U using Tapatalk

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