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More Gas Will Travel

Discussion in 'Intermediate CJ-5/6/7/8' started by mrtii, Oct 27, 2016.

  1. Oct 27, 2016
    mrtii

    mrtii 1972 cj51986 cj7 2022 Sponsor

    gilroy, California
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    Oct 3, 2016
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    165
    any one have any insight on installing under seat gas tank on a 72 cj5
     
  2. Oct 27, 2016
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
    Joined:
    Jul 18, 2013
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    5,593
    QUOTE="mrtii, post: 1305282, member: 92581"]any one have any insight on instaling under seat gas tank on a 72 cj5[/QUOTE]

    I would venture its pretty easy assuming you have original seat and mount bars. You will have to cut the filler neck hole In the standard early cj5 location. Aftermarket or used tanks are available as are the pickup and a tank strap to hold it in place. Not sure as I dont have an intermediate but the floorpan might need a little hole cut in in it to run the fuel lines and maybe the tank drain plug depending on tank.

    I put a rear tank in my early cj5 and kept my underseat as well. Really like the fuel capacity...i went from 10 to 25 gallons and well worth the effort. You will only go from 15 to 25 but with minimal effort its worth it.
     
  3. Oct 28, 2016
    mrtii

    mrtii 1972 cj51986 cj7 2022 Sponsor

    gilroy, California
    Joined:
    Oct 3, 2016
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    165
    Is it easy to get a transfer valve, and where did you set your up. Also does your gas gauge work for both, Thanks for comments, cheers
     
  4. Oct 28, 2016
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
    Joined:
    Jul 18, 2013
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    Here is my build page - link should take you to the top of page 3 where I did the fuel line switch.
    Fino's 1970 mini build thread

    I set mine dual tank up so that I have an electric switching valve that switches both the supply and return lines AND switches the sending unit wire so the stock gauge will read either tank. A lot of the older jeeps don not have return lines so they just put a manual valve switch/Tjunction in the line and do it by hand. But with return lines then you need to have a separate junction valve for that as well. Its cheaper to go that route, but then you either need a second fuel gauge or just run the first one till it runs out I guess (many of us don't actually have functioning fuel gauges anyway - they are a bit touchy and its easy to short them out). The pollack style (6 way) switch works perfect except for the fuel line sizes. Its set-up for 3/8 supply and 5/16 return, whereas on my early cj the lines are 5/16 supply and 1/4 return. So I had to add some step up and down barbed hose fittings. It works great so far.

    Others just use the 10 gal tank as a reservoir and have a little electric transfer pump to move fuel to the 15 gallon tank. I actually like this idea. Not as seamless as a single toggle switch, but probably way less hassle than running a second set of supply and return lines along with the electric switch, and your fuel gauge will only read the 15 gallon. In theory all you need is some fuel line to run from one tank to the other, but you will have to figure out some sort of inlet to get fuel into the 15 gallon tank. If that is your plan, you might think of getting the old style pick-up for the underseat tank that only has a supply outlet, otherwise you will have to plug the return nipple on the later style pick-up.
     
  5. Oct 28, 2016
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
    Joined:
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    5,593
    This would be the manual switch option - you would need two of these if you want to switch both the supply and return lines. These are prices but nice - probably can find something at the plumbing supply that is cheaper:
    Manual Fuel Selector Valve - Toms Bronco Parts

    This the 6 way electric switch that is like what I used - I got mine from Carquest or the like but they are all the same.
    Light Truck 6-Port Motor Driven Valve On Pollak
    The part # is in my build thread link above and you will need the 5 wire connector that is shown as well. It provides power, ground, and receives both sending unit wires from each tank, and sends out one wire to the gauge (and make sure gauge is grounded well to the housing and the regulator strap is working to the Temp gauge - that is where most burn out).

    Somewhere on the forum I have found a manual 6 way valve - but its pricey as well and wouldn't switch the fuel gauge of course.
    Here is an example: Groco Fuel Valve - 6 Port - Bronze - Fittings, Parts & Accessories - Fuel System - Engine Systems - Downwind Marine
     
  6. Oct 28, 2016
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
    Joined:
    Jul 18, 2013
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    5,593
    Just saw - these look like your first posts. Welcome to forum. Feel free to post up in the Introductions thread forum and show some pics as well. I am about as unknowledgeable as can be around here but others can give you lots of help. Quite a few know the intermediate years very well (Tim comes to mind but there are certainly others). They can let you know if there would be any fitment issues I am unaware of with tank under the seat but that should be the very easy part. Fuel lines and switches is where it takes a bit more time and thought. But if I can do it...anyone can do it.
     
  7. Oct 28, 2016
    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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    I added an under-seat tank to my 1973 CJ-5 n 1973. As projects go, it's easy. The main issue is the under-seat tank does not support vapor recovery, and fuel return is an issue, if you have that line. Installation is striaght-forward. I did not weld the filler insert to the body, instead choosing to use countersunk screws then filling their heads with putty. The area was sprayed with touch-up paint to match the original color. I put the 3-way valve in the middle of the floor at the driver's feet and did not connect the tank sender. I would run out the under-seat tank and then switch over.

    I would also warn that the under-seat filler does not seal very well, and I always had gas smell and occasional dripping on the side of the Jeep. Vapr recovery is a great system, and you mostly give up all the advantages of vapor recovery when you add the under-seat tank.

    Today, I would consider one of the oversized tanks from MTS instead. It reduces the break-over angle, but it preserves the significant improvements you get with the under-floor tank.
     
    Last edited: Oct 28, 2016
  8. Oct 28, 2016
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    USA
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    I went with a rear mount 15 gallon. I am VERY happy with it.
     
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