Fuel vapor separator..is it nessecary?

1971 - 1974 Mopars

  1. Notaclue

    Notaclue Member

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    Heard mixed answers on this, but is the fuel vapor separator nessecary? Or can you just plug the 4 ports on the tank and be good to go? Interested to see the replies, thx in advance.
     
  2. bigmanjbmopar

    bigmanjbmopar Newb with a view

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    No you don't need it for your car to run but if you want to be correct it should be there. What year and car is it?
     
  3. idrivemopar

    idrivemopar Well-Known Member

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    You could end up with vapor lock or over pressurization of your fuel tank if you don't have one, and you plug the holes on the tank. The vapors need to go somewhere, and with plugged holes and a tight fuel cap there is no where for vapors to go.

    The vapor separator allows the vapors to be recovered in the charcoal canister and then pulled into the carb and burned while not allowing liquid fuel to escape into the vapor recovery system.

    If yours is good, i.e., no holes in it, and you can hear the valve move inside it, most likely still usable. I refurbished mine by soaking it in evaporust for a couple of days to get both external and internal rust out of it, Once rust was gone, I rinsed the inside with wd40 to remove the evaporust residue and to keep it from rusting internally whilst I waited to reinstall. The outside I cleaned with brake clean, let dry, premiered and painted.
     
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    • Notaclue

      Notaclue Member

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      It's a 73 rr clone (satellite) with a 318 bored and stroked. I have a Holley blue electric fuel pump I'm getting ready to put on and I want to make sure the fuel system is good to go. I don't have the canister that goes with it but I have a separator off of a dodge polara that I can use if need be.
       
      Last edited: May 18, 2014
    • Notaclue

      Notaclue Member

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      I have a vented fuel cap, is that enough to make sure vapor lock doesn't occur? If not what can I do? Anybody have a diagram by chance?

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      Can I just run a small hose to a point above the tank with either a filter or relief valve on it?
       
    • sleepar

      sleepar Well-Known Member

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      Vapor lock is when the fuel gets hot... not really the same... I would keep the can and block off the carb vent by putting them together at the can. With out it you can pull a vacuum with the fuel pump or get dirt in the tank from an open line.... I was considering putting one on my 67 because it only has a vent in the cap and moisture gets in and the can filters it out some

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      Yes just keep it all out side the car.... it will smell of fuel and in extreme temp changes may drip fuel but that will replace the can.
       
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      • idrivemopar

        idrivemopar Well-Known Member

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        Vented fuel caps and original style caps with pressure safety valves only work when the tank is less then full, otherwise the fuel blocks vapor from escaping through the filler tube.

        Just a word of advice, when it comes to safety systems or fuel related systems, circumventing the original engineering for the system unless its improving the system is not always a good idea, and just wanted to say, and not trying to knock others advice on the board, but know what outcome of doing so before making changes that are not to specification and could create other unanticipated issues.

        I'm a stickler as some of you know for doing things properly.

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        I would not recommend this at all, three reasons, one, you may end up with fumes in the trunk or cabin of the car and breathing fuel vapor is hazardous, two, a trunk or cabin with fumes and a spark, not a good thing. and three, venting vapor next to the exhaust is trouble just waiting to happen, especially if you get a back fire and have an exhaust leak, then you might have some more serious problems.
         
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        • bm02tj

          bm02tj Well-Known Member

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          It does not pay to reinvent the wheel unless you can make a square one work or improve it
           
        • Notaclue

          Notaclue Member

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          Picked up an inline fuel filter and some tubing earlier, going to make a vent to sit above the tank near the rear of the car if I can't get the separator working. Going to do some more research on the subject first. Hope to hear more opinions on this subject though. Thanks again all.
           
        • Notaclue

          Notaclue Member

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          I think a more prudent thing to ask at this point is whether or not it's a better idea to have some kind of vent routed outside of harms way rather than hooking up the separator which just runs in the engine compartment without a canister
           
        • Dr HEMI

          Dr HEMI Member

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          Where does the vent line from the fuel vapor separator terminate at the rear?
          I have added the vapor separator but it is on a '70 with no canister or recovery
          system. It does not go to the tank vent? I can't find a diagram anywhere.
           
        • Kernel Sanders

          Kernel Sanders Well-Known Member

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          Here ya are!

          Emission Controls.jpg

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          Sorry about the size will try to edit

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          Hope this is better

          Emission Controls.jpg
           
        • Dr HEMI

          Dr HEMI Member

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          Wow! Thanks!!! Not exactly what I needed though.

          I have the vapor seperator canister by the fuel pump with one line running to the back.
           
        • 67 coronet

          67 coronet Well-Known Member

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          that will work fine.have done several sealed fuel cell vents like that with no prob.recirculating the fuel venting to be burnt by the eng was the beginings of modern smog devises.if venting to the outside rear was a problem my 67 would have blown up a long time ago since it just vents out the cap.
           
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