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cant switch tanks...

Discussion in 'Chevy Trucks' started by spongebob, Nov 6, 2003.

  1. spongebob

    spongebob Senior Member
    Messages: 102

    i have a 86 C-30 454 with dual fuel tanks..i have replaced the indash switch, still cant get one side to feed...when i switch the tanks, the fuel guage dosnt register the full tank. i have disconnected the plug at the fuel valve and measured the voltage on each plug(5 each) i get voltage on the same plug when i switch the switch....voltage(8.5dc/volts) on the 2nd plug in, and none on the rest ..i have tried following the wires from the switch on the dash, but my head seems to be too large..

    before i get drunk and look for my guns to clean, can some one give me a idea how to trouble shoot this problem?? thanks in advance..:help:
     
  2. TomatoRedGMC

    TomatoRedGMC Member
    Messages: 39

    i had this same problem with my dual tanks. but replacing the switch fixed for a while....now when i switch, it goes way past F, and never comes back down....i know for a fact its still feeding of that side, though....i guess i'm curious, does you gauge flicker at all? does it go way past F? maybe its the sending unit itself....
     
  3. spongebob

    spongebob Senior Member
    Messages: 102

    Tomato, no my gauge dosnt move at all when i switch tanks..

    seems like i should be getting a voltage reading on one of the other post on the electrical connection when i switch, but it dosnt..:confused:
     
  4. TomatoRedGMC

    TomatoRedGMC Member
    Messages: 39

    spongebob,

    Cna you hear the actuator move when you flip the switch? I can hear mine, thats how i know it is switching.......if you can't hear it, either the switch you got is bad, too, or the module itself might be bad, or the wiring to it. the 'switcher' is located under the passenger side tank on mine, hard to get to w/o the bed off. been down this road this summer. there is a ground wire plug on the sending unit itself, i think runs back to the switch i think....it looks like a little nut on top of the sending unit, the connector looks like a 'cap' hope this gives you enough info to go further! ;)
     
  5. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    so how is living in a pineapple under the sea? :)

    I have only jacked with dual tanks once but.....If memory serves me correct there is a hot with ign and a hot with one tank on and a hot with the other tank on and then the wires for the senders going into outa the selector valve.

    When mine first started shooting craps it was the switch, I took it apart, spent 15 minutes looking for the 2 little springs that shot out and almost took out my eye, cleaned it put it back together and it started working. But then once it started working and the little vale operated for the first time in a couple of years it went to hell.

    I would take the switch apart so you can see what wires to jump to eliminate the switch from the equation. Now with your key on you can test your plug going into the valve. You can swap back and forth hopefully and figure out if its a problem in the valve or elsewere. If you dont get one constant hot and 1 other hot that switches depending on what wire you bridge then my memory is shot or something is really fubar and you need to get ahold of a wiring diagram to figure out wich is the case. If your really cheap and cant find a diagram on the net you can cruise donw to parts america or the like and look at a helms and decide you dont really want to buy it anyway. Or go to the library.

    Once you figure out if its the switch/wiring somewere/or valve its a fairly easy fix.

    Are you sure that your fule tank isnt feeding/selector valve isnt switching? Or is it just that the fule guage is acting wierd?

    PS drinking beer and handling guns while chasing electrical gremlins is bad for the sheet metal :gunsfiring: :D
     
  6. TomatoRedGMC

    TomatoRedGMC Member
    Messages: 39

    Too funny, ratlover!! :D
     
  7. spongebob

    spongebob Senior Member
    Messages: 102

    ill have someone do the switching and ill listen for a click...ill be back later today..thanks guys..
     
  8. mrzulu

    mrzulu Junior Member
    from florida
    Messages: 18

    without knowing where spongebob lives i would say there is corrosion at the connections at the tanks... copper corrosion does funny things...

    MZ
     
  9. mrzulu

    mrzulu Junior Member
    from florida
    Messages: 18

    living under a pineapple in the sea is salty

    it's bad for the gremlins handling sheet metal chasing electrical guns drinking beer!


    MZ
     
  10. spongebob

    spongebob Senior Member
    Messages: 102

  11. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    so are the tanks getting switched and just not the guages? or nothing working?
     
  12. spongebob

    spongebob Senior Member
    Messages: 102

    its fecking snowing, cant get to them..but i have a feeling its under the dash cause switching produces no voltage changes at the connection under the truck..

    i live in the sierra nevada mountains..
    thing that pisses me off is my haynes piece of crap manual dosent show dual tanks on the electrical cartoon..

    :angry:

    but i think a beer will go along ways to help me figuring out washappining..:drinkup:

    keep the ideas commin boys...i know theres a answer out there somewhere..
     
  13. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    You getting power to the switch? you try jumping it at the switch to see if you get juice at the valve?
     
  14. spongebob

    spongebob Senior Member
    Messages: 102

    heres the deal, i get voltage to the connector going into the switching valve(this is a 5 pronged plug...but when i switch to the other tank, i get voltage to the same prong...shouldnt it(voltage) show up on another prong???
     
  15. mrzulu

    mrzulu Junior Member
    from florida
    Messages: 18

    sir sponge... i have pondered this for a couple days now...
    logically there are two possibilties...
    1. dead short in the wiring
    2. bad switch in the fuel pump
    check fuel pump solenoid inbetween tanks
    MZ
     
  16. spongebob

    spongebob Senior Member
    Messages: 102

    mrzulu, a dead short, I'm getting voltage on one leg in the connector..(there doesn't seem to be a fuse in this circuit).

    the fuel pump is a external pump mounted on the frame.

    if i could get a cartoon of the circuit, that would be helpful..

    what do you think of it being a bad switching valve??? I'm thinking of jumping the post that has voltage to one of the posts on the valve it self..if the gauge comes on(for that side), then maybe its the valve its self...:cry:
     
  17. mrzulu

    mrzulu Junior Member
    from florida
    Messages: 18

    is the second tank after market?
    dead shorts can still show voltage in late model vehicles
     
  18. spongebob

    spongebob Senior Member
    Messages: 102

    no, the truck has dual tanks as standard,,
     
  19. ratlover

    ratlover PlowSite.com Addict
    from IL
    Messages: 1,325

    Going off memory there are
    1 constant hot with the ign on (pink)
    2 wires(light green and dark green) that are hot depending on the switch to flop between tanks.

    This was how it was on my 83

    oh and the senders wires and all that other stuff.....
     
  20. spongebob

    spongebob Senior Member
    Messages: 102

    OK, i replaced the switching valve ($100) that didnt work, now im thinking i have a loose/missing ground wire !! ill let ya know.

    ps, if anyone knows the designer of the installation of that valve or the guy that signed off on the design, id like to have there name and phone #.:angry: