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Fuel Line Question - Dauntless V-6

Discussion in 'Early CJ5 and CJ6 Tech' started by Dave B, Apr 7, 2015.

  1. Apr 7, 2015
    Dave B

    Dave B Frankenjeep '67

    Northern Minnesota
    Joined:
    Nov 10, 2009
    Messages:
    650
    Here's what I have: 1967 CJ5 FrankenJeep with a Dauntless V-6. That is not saying it is a 1967 V-6. I believe it to be a 1969 V-6. I'm replacing gas tank and lines—the last leg of a long rebuild. My questions are at the bottom.

    The old, leaky steel gas tank has two bottom-of-the-tank threaded female fittings—one will receive 1/4” and the second receives 3/8”. Top of the old tank has one threaded female fitting and will receive 1/4”. The six-bolt fuel gauge float unit has no outlet pipe, the only thing it does have is a screw to receive the sending unit wire.

    The fuel pump is as seen in the Jeep (SM-1046) Service Manual—page 130, fig, E-33. It has three connecting points: (1) Fuel Outlet (threaded --goes to carburetor), (2) Vapor Return (receives 1/4” rubber hose) and (3) Fuel Inlet (receives 3/8” rubber hose).

    The old fuel system lines [by previous owner] are not original routing as per Jeep Manual—page 110, fig E-2.
    The bottom-of-the-tank 1/4” threaded female was plugged. This fitting has the curved-tube attached to it, which is inside the tank.
    The bottom-of-the-tank 3/8” fitting was connected to the fuel pump inlet.
    The top-of-tank 1/4” fitting connected to the fuel pump vapor return. The line routing dropped over the left edge of the tank [tight between tank and body interior] and through the floor.
    Fuel line(s) routing between tank and fuel pump are all at frame-level, the only line, at the engine, ever higher than the fuel pump is the outlet line to the carburetor.

    My new steel gas tank (JC Whitney) has the same two bottom-of-the-tank female fittings as the old tank, but no top-of-tank fitting. It, too, is for a six-bolt fuel gauge float unit.

    So, using the fuel pump, fuel gauge float unit and the new replacement tank described above—here are the questions???

    1) Where does the fuel pump Vapor Return have to go into the gas tank—top or bottom?

    2) If the top-of-tank is the necessary answer, and it seems so – I must drill and braze. Then what are the two bottom-of-tank fittings for?

    3) Is there a different six-bolt fuel gauge float unit that would be a remedy? My rusty metal and cork type is pretty tired-looking, to put it kindly, anyway!

    Better stop my questions here! I just successfully finished complete rewiring, from scratch, but this “simple” fuel system has me wondering. I'm not looking for original, any help appreciated! --Thanks!
     
  2. Apr 7, 2015
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Aug 10, 2003
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    1) Vapor return goes to the top of the fuel tank. If you have the later sender, there will be a nipple in the sender for the return line. It just dumps in.
    2) There are new (late 60s?) and old (before) tanks. The new tanks have a pickup tube and return in the sender plate, and use a lock plate and o-ring. The older tanks have six screws and a gasket, and feed from the bottom, IIRC. I don't know why there are two bottom of the tank fittings.
    3) Not that I know of. New or old tank is the only alternative.
     
  3. Apr 7, 2015
    Greevesman

    Greevesman Member

    Napa, Ca
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    Oct 12, 2014
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    417
    Is the second one on the bottom a drain?
     
  4. Apr 7, 2015
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    Nov 22, 2003
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    8,102
    Sounds like you have a modded F4 fuel tank.

    The bottom 1/4" with the bent tube inside the tank would have been the original fuel out- it should actually be a reverse flare fitting.

    The 3/8" on the bottom was originally a drain fitting.

    H.
     
  5. Apr 7, 2015
    oldtime

    oldtime oldtime

    St. Charles,...
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    Aug 14, 2006
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    3,466
    Apparently your tank is not equipped to accept a gasoline vapor return tube.
    The vapor return is normally located at the top of the tank.

    The smaller fitting is for gasoline supply to the fuel pump. It has a an internal pick-up tube attached to it.
    The larger fitting is a drain.

    No if your tank is set up for a 6 bolt tank unit then you must use a 6 bolt tank unit.

    Earlier Dauntless systems did not use the vapor return.
    You can eliminate the vapor return tubing if you prefer the early system.
    An early Dauntless fuel pump only has the inlet and the outlet fittings.
    The early Dauntless fuel pumps do not have the vapor return port.
     
  6. Apr 7, 2015
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Sending unit for a V6 tank with a return line -

    [​IMG]

    From the MTS site http://www.mtscompany.com/jeep.htm

    AFAIK there is no source for the V6-style tanks in steel. MTS makes a plastic one.
     
    Last edited: Apr 7, 2015
  7. Apr 7, 2015
    Dave B

    Dave B Frankenjeep '67

    Northern Minnesota
    Joined:
    Nov 10, 2009
    Messages:
    650
    Thanks everybody!

    So, with the mixed bag of parts that I have to work with, I'll connect--

    1) the fuel tank 3/8" drain to the 3/8" fuel pump inlet
    2) put a plug in the bottom 1/4" fitting
    3) cap/plug the fuel pump 1/4" vapor return-hose-nipple-stub
    4) connect fuel pump outlet to carburetor

    Then we'll see about performance. Ideally, in the future, it should have a compatible tank and fuel pump.
     
    Last edited: Apr 7, 2015
  8. Apr 7, 2015
    Dave B

    Dave B Frankenjeep '67

    Northern Minnesota
    Joined:
    Nov 10, 2009
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    650
    I've re-thought the incorrect fuel pump to incorrect fuel tank connections on my 1967 CJ5. Believe I'll weld/braze, while the tank is new/unused/non-explosive, a 1/4”fitting in the top of the tank and have it for the fuel pump vapor return.


    It would probably work without a vapor return line in Minnesota's cold, and low elevation, but a line should be a plus; they started putting return lines on the Dauntless V-6 for a reason, one can suppose.


    Because of comments to this thread, I checked the label on the box of the new fuel tank and it is noted for a “134CI 55-69 CJ5/6”. So, there was inexperience on my end, and with the salesperson, and the previous owner's“Frankenjeep”/non-original set-up was a negative reference, in placing an order. I've no plans to return the tank, as it been months since received.


    I have so many non-original/Frankenjeep features on this Jeep it's part of the charm, I guess. I've written its own one-of-a-kind owner's manual!
     
  9. Apr 8, 2015
    AKCJ

    AKCJ Active Member

    Fairbanks, Alaska
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    Aug 12, 2003
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    1,035
    I'm not familiar with the "vapor" return line. On my 70 there's a supply and return from the pump in addition to the outlet that goes to the carb.
    Anyway, the return line was run to a tee fitting in the supply line when I got my rig. It worked fine but I went ahead and ran it back to the tank just for good measure. I just mention this as an option.
     
  10. Apr 8, 2015
    mortten

    mortten I can’t put my finger on it 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Peninsula, Ohio
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    I had vapor lock problems when I didn't have the return line hooked up. Once I hooked it up problems went away
     
  11. Apr 9, 2015
    Chevallier87

    Chevallier87 Member

    Boise Idaho
    Joined:
    Apr 21, 2012
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    230
    I'm also re-routing fuel lines. What sort of pipping would you all suggest? Steel lines from the tank to pump/ rubber lines? Avoiding heated areas and dramatic climbs?
     
  12. Apr 9, 2015
    commanlerwrangdo

    commanlerwrangdo Member

    Cleveland, Ohio
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    Feb 10, 2014
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    470
    I use the galvanized roll line and cut to exact length. Run along the frame away from heat sources and moving or rotating parts.:p
     
  13. Apr 9, 2015
    jwmckenzie

    jwmckenzie Sponsor

    Boston, MA
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    Mar 16, 2012
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    568
    There is a thread on here some place where the return line fitting was put into the six bolt sending unit. No worries about welding on a fuel tank.
     
  14. Apr 9, 2015
    Project71-5

    Project71-5 BACON

    Gypsum, CO
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  15. Apr 9, 2015
    Steve's 70-5

    Steve's 70-5 Active Member

    Louisville, Ky
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    Nov 12, 2009
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    I took a 6 bolt tank and had a sheet metal shop cut the locking ring assembly out of my old tank and weld it into the new tank
     
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