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anyone with a 73-77 dual tank pickup,

Discussion in 'The Garage' started by R72K5, Mar 10, 2006.

  1. R72K5

    R72K5 Banned

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    anyoen who has a 73-77 dual tank pickup is there anyway you could please please please look on your rig real quick and see at the tank switcher valve assembly if the bright green wire plugs into the valve assembly, or if its the tan/white stripe wire ?

    need to know where the tan/white stripe wire goes also

    the solid tan one goes to the RH tank

    and the blue one goes to the LH tank

    my bright green and tan/white stripe wires are cut off right by the tank switcher valve assembly and no wire is plugged to it

    help ?

    hope you understand what im asking

    just wanting to know where these two wires plug to, real simple

    thanks for anything, i appreciate it, id love ya forever(j/k)
     
  2. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    If I remember correctly, the green wire goes to the solenoid, and the tan/white wire is for the sending unit.
     
  3. skidpan

    skidpan 1/2 ton status

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    i COULD USE THE ENTIRE WIRING DIAGRAM AS WELL... i DONT EVEN KNOW WHERE THE WIRES FROM THE SWITCH GO.. i CLEANED UP UNDER THE DASH AFTER REMOVING THE HEATER CONTROLS, but dont know where to plug the harness back into.. sorry abut the caps guys..
     
  4. R72K5

    R72K5 Banned

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    hi skid, the wires from the dash switch go straight(non-interrupted) through the firewall and down the drivers side frame rail to the tanks and valve assembly deal


    at least in the early mid 70s anyways

    i am pretyt sure the wiring and valve units changed by the time the late 70s came around

    im really pretty sure anyways

    at least 78 and up trucks i have had in the past with dual tanks were alkot different than this 77 is

    and i cant remember on my past pre-78 trucks where the valve was located and what harness wires they had

    been too long.


    but i rmemeber that in 78-up the valve unit is mounted directly under the rear cab wall and right in the middle of the truck

    unlike this 77 that has it mounted way over on pass side just to the inside side of the frame rail, under the cab towards the rear of the cab almost under the rear cab wall
     
    Last edited: Mar 10, 2006
  5. R72K5

    R72K5 Banned

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    Sierra, ok thats VERY good to know, am halfway there now !! :D

    now down to the white striped tan wire, hmm

    there is already a solid tan wire to the tank- no stripe

    this striped tan one is the one that is cut off dead end just like the green one is, goes to nothing, hacked off

    does your rig have two tan wires under there also ? one should be solid and the other striped just like mine


    this striped tan wire just isnt making any sense,
    it also goes straight to the dash switch along with all the rest of the wires-
    1. green wire
    2. solid tan wire for RH tank
    3. and the light blue wire for the LH tank

    thats it, nothing else under there in the harness, they are all wrapped together, all looks fine, cept for the hacked off striped tan wire and the hacked off green wire, at the valve assembly unit



    thanks for any further info! :D
     
  6. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    My 80 used to be dual tanks (now a single burb tank between the rails out back) and used a system similar to yours. Now, as far as I can remember, the switching solenoid had only a single wire to it, which I do believe was green. The solenoid self grounded to the frame.

    Now, this is where it gets confusing for me. My truck had a 4 pin connector on the firewall that went to the tank switch inside of the truck, along with a pink wire that ran from the engine harness back to the tank.

    To make my sending unit work, I had to hook my tank up to the pink wire running down the frame rail, but after I unhooked the dash connector, the fuel gauge no longer worked.

    Doubt that helps you much, but I'd really need to be able to see the wiring myself to be able to help you very much :(
     
  7. R72K5

    R72K5 Banned

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    yeah see 80 is probably a whole different thing im sure,
    where is your valve switching assembly located at under your cab ?
    under the middle of the cab, or over on pass side by the frame rail ?


    the 77's had no pink wire on the framerail, the two tank wires are blue, and solid tan

    the valve assembly is way over on pass side next to the frame rail,

    the only pink wire is from the dash switch to the fuse panel

    thats it

    this is the older style harness and dual tank setup, not like the later stuff, sometime before 80


    apparently no one on this forum has a 73 to 77 or 78 dual tank pickup, i guess i am the only one


    hmm, im like sad or something :(


    thanks :D
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Too bad I just tossed my 76's harness -- It had dual tanks.

    My 80 had the valve mounted to the pass side frame rail near the rear of the cab, but I scrapped the old 2wd frame almost a year and a half ago now.
     
  9. R77K10

    R77K10 Banned

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    ttt

    just need to know where the tan- with white- stripe wire is supposed to go under there

    thanks
     
  10. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    OH YAY!!!!! my long drawn out research will pay off... I did a stupid drawing in ms paint when I had problems and I got ya covered... hold on lemme get it.....
    :haha:
     
  11. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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  12. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    I know my pic is like a 3 year old did it but it works.. I even put the items in their corresponding locations...

    wiring gets tricky.....

    back in the day.. when you had a single tank truck.. they ran the brown wire from the gauge to the float......

    however... to add the dual tanks they just had a different plug.....

    this is how my truck was
    so
    Pink wire on switch (2 prong side) goes to fusebox
    Brown gauge wire goes to switch (3prong side) as blue on the middle prong..(not sure why mine was brown then blue....)
    one tank to top prong (left)
    one tank to bottom prong (right)


    TOOK ME SO FRICKEN LONG TO FIGURE IT OUT!!!! somehow mine was wrong.. dont know how or when that happened.. but I got mine fixed in 9/20/2003...:haha:
     
  13. R77K10

    R77K10 Banned

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    wow im really confused now

    your blue wire didnt run from driver side tank to the dash switch ?

    mine does

    the damn second tan wire is whats messing it up

    why are both your tanks running a tan wire ?

    yours are brown- mine are tan, one is striped and the other isnt


    im gonna have to pull my freaking dash apart to see what the hell wire they ran to the circuit panel for the guage, because none of the damn wires in the harness go to the dash, which makes no sense whatsoever
    both the tank wires dead end at the switch and thats it

    they all only run straight from under the truck to the dash switch

    damn

    dual tanks are just one those things that make you want to take C-4 to the rig

    missing a damn wire from the switch to the guage

    but nothing is cut in the cab

    grrrr.....



    thanks
     
    Last edited: Mar 20, 2006
  14. R77K10

    R77K10 Banned

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    heres a quickie of exactly how mine is currently


    [​IMG]

    the guage isnt even in the circuit anywhere and nothing goes to the valve




    switch to Lh tank is blue
    switch to RH tank is solid tan
    switch to fuse panel is pink
    switch to (hacked off near the valve) is green
    switch to (hacked off near the valve) is the other tan- in which is striped

    fuse panel= FP
    switch= S
    valve= V


    thanks
     
  15. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    well one step at a time...

    i said brown wires for tanks.. but yeah mine had stripes too.. either they ran out of tan or whatever but the pic should give ya an idea that each tank

    needs to be grounded
    other lead runs back to switch


    I know it is confusing cuz it totally had me going for months.. but I finally got it.. think of this logic...

    find the wire in your dash for the gauge... it needs to run to the switch....
    your switch needs power.... so fusebox to switch....
    dual tank solenoid needs power to open or close.. believe voltage makes one tank then flick off and solenoid snaps the other way making the other tank work...


    now the switch is a rocker switch so think of this...
    in the up position.. the gauge needs to point to a tank... so middle pin will do that.. and the top pin will be the wire to goto the tank....
    then in the down position same theory... gauge needs to report it and wire needs to goto the tank......

    dont really look at colors too much... I color coded what I had...
    I went from a dual tank truck to a single tank cab and back to a dual tank setup.... so mine was messed up really bad....


    here are some more pics I took... these are 2+ years old

    [​IMG]

    this one is a big pic but same as above... maybe you can look closer...
    http://68.36.135.34/PROJECT_NJLEGAL/9_22_2003/switch2.jpg


    http://68.36.135.34/PROJECT_NJLEGAL/9_22_2003/tank1.jpg
    http://68.36.135.34/PROJECT_NJLEGAL/9_22_2003/tank2.jpg


    if ya need me to look at anything on my truck I can do that.... lemme know...
    it is confusing and had me scratching my head....
     
  16. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    p.s. those last pics I just posted are wrong.. that is how mine was at first.. dunno who the hell ever did it that way...


    has your gauge ever worked? that pic looks all screwed up!!!!
    if not I would do what I did... take both thanks out....
    hookup wires externally and all.. and figure it out.... :crazy:
     
  17. dyeager535

    dyeager535 1 ton status Premium Member

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    It "seems" simple now to me. :)

    Your fuel gauge wiring is hooked up right, but the portion to the gauge from the switch is cut. (I'm assuming those two wires near the V are cut ends) If your wiring is consistent with what others have said, the tan "dead end" wire is likely the gauge wire. If you've got a spare gauge lying around, hook it up externally and test that wire with it. (or use a multimeter)

    If the one cut wire is the fuel gauge, the other has to be the solenoid wire. Flipping the switch back and forth with a voltmeter on that wire should prove that it is. You said you have 12V on the pink wire from a previous test, so that means the switch is getting power.

    Makes sense in my head anyways.
     

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