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Fuel cut-off switch

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by CK5, May 7, 2001.

  1. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Any ideas on how to do a fuel cut-off switch with FI?

    Steve
    [​IMG]
    Mall-Running poseur 4x4 with curb-feelers
     
  2. FRIZZLEFRY

    FRIZZLEFRY 1/2 ton status

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    I have a 68 Mustang with EFI and for anti theft purposes I put a switch on the hot wire going to my fuel pump relay.

    All work and no play makes Frizz a dull boy.
     
  3. BIGJ

    BIGJ 1/2 ton status Author

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    Put a switch on the tan wire to the fuel tank. That is the power wire for the fuel pump. No power, no fuel pump prime or running engine:)

    BIGJ
     
  4. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Should I just extend the tan wire into the cab with a hidden switch some where?

    Steve
    [​IMG]
    Mall-Running poseur 4x4 with curb-feelers
     
  5. BIGJ

    BIGJ 1/2 ton status Author

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    That's what I plan on doing. I will probably run a wire to a switch in the cab. Where to put the switch, that's the question.

    BIGJ
     
  6. K5Junkie

    K5Junkie 1/2 ton status

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    I believe there is a fuse for the fuel pump in the fuse panel, so there should be a wire under the dash that you can splice into and install a switch. I have a switch hidden under my dash that the previous owner installed. I went out to look where it went to but i can't see the wire, only the switch. He did i good job of hiding it!

    [​IMG]
    <A target="_blank" HREF=http://k5junkie.coloradok5.com/>http://k5junkie.coloradok5.com/</A>
     
  7. K5Junkie

    K5Junkie 1/2 ton status

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    Ok steve i found the wire...it looks like he connected it to the computer behind the glove-compartment. It is connected to the light purple wire with the white stripe. The wire is the second wire you can see coming out if the computer with the glove compartment flipped down. I hope this helps.

    [​IMG]
    <A target="_blank" HREF=http://k5junkie.coloradok5.com/>http://k5junkie.coloradok5.com/</A>
     
  8. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    Thanks Junkie
    I would think it would be the same for my 90 as well, to many rides getting stolen these days. [​IMG]

    Steve
    [​IMG]
    Mall-Running poseur 4x4 with curb-feelers
     
  9. 79Jimmy

    79Jimmy 1/2 ton status

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    Like FRIZ said I'd splice into the fuel pump relay circuit, either the relay ground or the low amp +12 volt trigger.

    James

    PS: Solder and shrink wrap all splices and connections for a trouble free future

    79jimmy@home.com
     
  10. lowlevell

    lowlevell 1/2 ton status

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    A little while ago some one posted a drawn out diagram here at CK5 on how to do this. I couldnt find it though. I too, need to know what the easiest way to do this(89' Sub). This job would not be difficult at all, but we need to know which wire to splice into (preferably under dash). Im currently in the process of killing my TA's starter lead, then will switch the manual fuel pump over to electric and kill it.

    89' Sub
    79' TA
    75' Chevelle

    One From None
     
  11. Sparky

    Sparky 1/2 ton status

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    For you fuel injected guys... I am pretty sure there is a 3 prong sending unit type thing where your oil pressure sending unit gos. It is designed to shut off the fuel pump when you loose oil pressure. (only electronic fuel pumps here) You could run a switch off of one of those lines. Correct me if I'm wrong, but I think this is how your fuel pump knows to shut off if you are not running the engine, but have the key on. I was thinking about putting one of those under the dash, but inside and behind the glove box. (Not on my truck, I dont have fuel injection) No one would find it there and it would be pretty easy to get to.

    Sparky

    ps: If you dont have one of those 3 prong sending unit things you can buy one at any parts store and wire it in. I have done it before, and its not too hard. It will minimize damage if you loose oil pressure and dont know it. It shuts the fuel pump a couple seconds after the pressure drops below about 5 psi.


    When all else fails... Check the blinker fluid.
    78 K-5
     
  12. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    Hey Steve you could mount the switch on the inside of your Tuffy security console, then it would be locked up...

    [​IMG]
     
  13. CK5

    CK5 In my underwear Administrator Premium Member GMOTM Winner Author

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    I thought about that.

    Steve
    [​IMG]
    Mall-Running poseur 4x4 with curb-feelers
     
  14. chevyfumes

    chevyfumes Court jester

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    Watch for the muzzleflash!
    Great minds think alike...

    [​IMG]
     
  15. pcorssmit

    pcorssmit 1/2 ton status

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    That sender (located near the distributor) DOES NOT cut off the fuel pump when you loose pressure. It is there as a fail safe, for when the fuel pump relay goes bad. Normally, when you turn the key the computer turns on the fuel pump for about 2 seconds to prime the system (TBI's bleed off pressure when turned off). When you hit the starter, the relay kicks on again, and stays on.

    The switch supples juice to the fuel pump whenever there is oil pressure. When the fuel pump relay goes bad, you have to crank the truck over for 5-10 seconds until you build up oil pressure. Then the switch sends power to the pump. It is a redundant system, so if either the switch or the relay goes bad, you can still drive the truck.

    It is easy to add a starter or fuel pump cutoff switch on these trucks.

    Steve, If you want to look at the wiring diagrams, give me a call, I've got all the factory books (HELM).

    Pete

    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
     
  16. prjt_blzr

    prjt_blzr 1/2 ton status

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    Here is something that I've done with several of my vehicles. I splice a fuse into the ground side of the fuel pump relay. I then place a switch into the ground side of the fuel pump relay. In the open position the switch does nothing. In the closed (armed) position the switch puts 12 volts through the fuse. Poof, the fuse blows and even if the thief finds the switch the relay does not have a ground to function until after the fuse is replaced. I think that this is more secure than just a hidden kill switch. Just my $0.02.
     
  17. 90K5

    90K5 1/2 ton status

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    I made one yesterday. I put it on the fuel pump ground by the left rear shock mount, and duct taped the switch (for now) to the frame. I'll hide it better later, but it works.

    90K5

    See my truck at <A target="_blank" HREF=http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502>http://albums.photopoint.com/j/Albumindex?u=1329584&a=9886502</A>
     
  18. mattman

    mattman 1/2 ton status

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    That purple with white wire sounds familiar. Mine came with a Prolock set-up. I traced it one day and it goes to the purple wire with white stripe but this connection point is under the dash in the back near the carpet. I think this is the starter kill? circuit because whenever I try to start it without the key it just flashes the lights - no starter, no nothing. Just hide it good because I traced this out in less than 2 minutes. All it takes is a jumper and this is useless. An idea my dad used was to use a useless switch (fog lights, dual tanks, etc.) that was factory but do not have the option. He would put a factory switch in this position and wire his starter to it. That way it looks factory to through off a thief with enough time to disable a starter kill.

    90 GMC Jimmy, 350 TBI, 700R4, 32's
    84 Bronco II 204,000 miles and counting...........
     
  19. dyeager535

    dyeager535 1 ton status Premium Member

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    If the fuel pump is on a fuse, why not just modify the fuse a little bit (like to easily clip onto your key ring) and pull it when you want the security? I guess its not real practical if you are all dressed up and such, but with a longer "handle" on the fuse, it should be no sweat. Plus, no wire splices, nor is any thief going to figure that out...they will LOOK for a kill switch, not a missing fuse.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  20. prjt_blzr

    prjt_blzr 1/2 ton status

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    You could just pull the fuse. But if you are dressed up or your wife is driving the vehicle you have to worry about getting dirty......... You could use a remote fuse like I do on my switch setup that is easy to get to and accomplish the same thing. I'm just lazy and find it easier to flip a switch to disable the vehicle knowing that if anyone tries to start the vehicle they will toast the fuse and have to reset both the fuse and the switch. It is just a matter of preference.
     

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