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Rear Fuel Tank On Cj3b

Discussion in 'Flat Fender Tech' started by RVSwisher, May 31, 2020.

  1. May 31, 2020
    RVSwisher

    RVSwisher Member

    Rochester, MN
    Joined:
    Jul 11, 2006
    Messages:
    105
    Has anyone installed a rear CJ5 fuel tank on a CJ3b? I know I will need to remove the draw bar and install a custom rear bumper.

    Will a standard CJ5 rear fuel tank fit?

    Thanks

    RVS
     
  2. Jun 1, 2020
    timgr

    timgr Jeepin' Nerd 2020 Sponsor 2019 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    21,063
    Kinda suspect it won't. The CJ-3B rear springs and rear frame are shorter than the CJ-5. CJ-5 Frame Modification on CJ3B.info
    You could remove the toolbox and put a tank on the passenger side. Thats been done a lot. Auxiliary Gas Tank on CJ3B.info MTS sells a plastic tank specifically for this. Or could build a tank that's 3" shorter than the CJ-5 tanks.
     
  3. Jun 2, 2020
    garage gnome

    garage gnome Rust polisher

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    2,168
    I had a 2A with a rear mounted tank and the rear axle kept hitting it.
     
  4. Jun 2, 2020
    44bz

    44bz New Member

    Oregon City OR
    Joined:
    Jul 30, 2018
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    38
    A friend of mine has put rear tanks in three 3b's that I know of. I can ask him what tank he uses. I know the two recent projects had plastic MTS tanks. I'm pretty sure he is using a CJ5 tank and mounting straps.
     
  5. Jun 2, 2020
    Buildflycrash

    Buildflycrash Member 2020 Sponsor

    Gulf Breeze FL...
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    Jun 5, 2007
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    1,320
    I have a CJ5 15gal I was planning to use on my 3B. I better watch this one....
     
  6. Jun 2, 2020
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Aug 13, 2015
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    I made my own, and it was a tight fit to make a tank that held 10 gallons and still had clearance.
     
  7. Jun 2, 2020
    73 cj5

    73 cj5 Not ready for the junkyard yet 2020 Sponsor

    Mississippi
    Joined:
    Jan 10, 2014
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    1,220
    Yea I can confirm a 74 cj5 tank won’t fit without interference. I’m considering a fuel cell again.
     
  8. Jun 2, 2020
    RVSwisher

    RVSwisher Member

    Rochester, MN
    Joined:
    Jul 11, 2006
    Messages:
    105
    Thanks for everyone's feedback. I am curious regarding which tank 44bz’s friend is using. I may look at a fuel cell or a custom tank as I am swapping a 225 and what EFI with will require me to install a return line.
     
  9. Jun 3, 2020
    44bz

    44bz New Member

    Oregon City OR
    Joined:
    Jul 30, 2018
    Messages:
    38
    He thinks it's the 78-86 MTS tank that he has used. Their website states it measures 23x16x10 so get out the tape measure. He removes the factory rear crossmember/bumper, bends the mounting tabs in the frame ends outward, then installs square tube inside the frame rail to act as the new crossmember. This provides a little more room for the tank and there aren't any clearance issues with the rear axle.
     
    ITLKSEZ likes this.
  10. Jun 3, 2020
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
    Joined:
    Aug 13, 2015
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    4,300
    That’s pretty darn close to my measurements, but the 16” could be an issue. I removed the rear crossmember on mine and replaced it with 3/8” flat stock. My tank is crammed between that and the crossmember under the bed, and my tank is 15 1/4” long. I did replace/redesign the frame horns to work with my springs, so maybe I made the new ones shorter? It’s been two decades, so who knows.

    My 3a frame measures exactly 16” between the under-bed crossmember and where the outside of the rear crossmember was, so maybe if the rear crossmember is removed and tubing added to the outside? It’d be tight, but possible.
     
  11. Jun 4, 2020
    jeepermc

    jeepermc Member

    Western WA
    Joined:
    May 25, 2011
    Messages:
    940
    I think the postal tank is slightly smaller than a CJ-5 tank. I think that's what's in the back of my M-38.
     
  12. Jun 4, 2020
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
    Joined:
    Mar 4, 2003
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    4,641
    I'm running a custom tank on the 3A as well as the '49 3A, but it's on a 5 frame. Had a regular tank in by a PO, but as stated, axle kept hitting it and finally split it out - that's when I went to the custom 1/8" steel tanks.

    Most all EFI that I know of for the 225 require a return line. You can get away with using a command module with the pump and return to it like the FI-Tech setups use. This is what we installed on my neighbor's 5. He kept the stock tank and already had a low pressure electric pump he was using (could keep the mechanical too).
     
    Buildflycrash likes this.

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