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Thread: anyone use a fuel pump kill switch?

  1. #21
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    True, just another wire won't do it. Since GM uses oil pressure as part of the fuel pump circuit it might be a little more involved, unless there is a 12 volt relay somewhere, sending power to the pump. The simplest way would be to just put the inertial switch in series directly to power the pump if it is capable of carrying the current of around 10 amps. That's the way Ford did it on a lot of vehicles, using the 3rd terminal to turn on a dash indicator light. It shouldn't see any duty cycle, which a relay would need to do every time you powered it up. I have had to troubleshoot many intermittent electrical problems that ended up being caused by a bad relay contact. Much easier with only a switch in the way. It was pretty easy to troubleshoot a relay on a machine tool back when you could check relay contacts by manually operating a relay by pushing it in with a screwdriver to check contact resistance. Too bad cars were not designed that way.
    Last edited by 55 Rescue Dog; 01-11-2020 at 06:36 PM.

  2. #22
    Registered Member chevynut's Avatar
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    I just got back from being gone for a few days and looked at my Holley C950 schematics. My ECM does supply power for the fuel pump relay. Apparently the LS ECM DOES supply power to the relay also, like other GM ECMs in earlier EFI engines. Here's an LS1 schematic.

    Last edited by chevynut; 01-11-2020 at 07:37 PM.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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  3. #23
    Registered Member chevynut's Avatar
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    What voltage is your buzzer designed to work on and how much current does it draw? The LED should easily light up if you have it wired right. Connect the "common" terminal of the inertia switch to the ECM output. Connect the NC terminal (the one that's shorted to common when the inertia switch is set) to the fuel pump relay coil. Connect the NO terminal to the buzzer and the light. The LED is polarity sensitive so you need to be sure it's wired correctly. I don't know about the buzzer. Note that the buzzer and light will ONLY be on when the ECM is trying to turn on the pump.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  4. #24
    Registered Member chevynut's Avatar
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    Paul, which buzzer/LED are you using. Also, what is the brand and P/N of your fuel pump relay? I'd like to look at the specs. Those are usually 12V relays and I'm surprised it works at 5V on the coil.

    You could always use another relay to turn on the power to the buzzer but it doesn't seem to me like you should need to.
    Last edited by chevynut; 01-11-2020 at 07:19 PM.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  5. #25
    Registered Member chevynut's Avatar
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    Here's some info.....you should see 12V on the ECM fuel pump control wire according to this:

    https://ls1tech.com/forums/conversio...-question.html

    Also, a 12V relay should have at least 9V on the coil to operate correctly.

    https://forum.digikey.com/t/understa...ifications/946
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

  6. #26
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    It looks like the inertia switch should be in series with DK GRN/WHT wire 465 output from the PCM, and not the control input to the PCM? Assuming it's 12v going to the relay coil.

  7. #27
    Registered Member WagonCrazy's Avatar
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    Here's how I wired it...
    the light and buzzer now work when the switch is activated (thereby removing power to the fuel pump relay, which results in shutting off the engine).

    IMG_5772.JPG

    Link to the Inertia Switch https://www.ebay.com/itm/183727849647

    Link to the LED light/buzzer https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    Last edited by WagonCrazy; 01-14-2020 at 06:23 PM.
    1957 Nomad- LS1/T56 on C4 chassis
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  8. #28
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    Glad it works, but you should work on your schematic a little maybe.

  9. #29
    Registered Member WagonCrazy's Avatar
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    i'm not an electrical engineer by any stretch. I'm a hack and trial and error guy with sometimes burnt fingers to show for it. I'm expecing the full wrath from chevynut when he looks at my drawing and shitz...
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  10. #30
    Registered Member chevynut's Avatar
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    Paul, I'm not understanding your schematic. I can see how the fuel pump relay works. But I don't see how the buzzer can work with 12V on both sides of it. Where is the buzzer ground?
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

    You can see my 56 Nomad build here http://www.picturetrail.com/chevynut

    For affordable C4 Corvette Suspension conversions for your car, visit http://www.classicedgedesigns.com

    Other vehicles:

    56 Chevy 2-door BelAir sedan
    56 Chevy 210 4-door sedan
    57 Chevy 210 4-door sedan
    1961 Willys CJ3B Jeep
    2001 Porsche Boxster S
    2003 Chevy Silverado 2500 HD Duramax

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