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Thread: anyone use a fuel pump kill switch?

  1. #41
    Registered Member chevynut's Avatar
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    Nov 2011

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    Paul, I think connecting the buzzer to switched power makes more sense and the benefit is that as soon as you turn on the key it tells you the switch is tripped. Probably not a bad way to do it if the ECM really does hound the output when not outputting 12v. I’ll have to check mine to see if it works that way too.
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension


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  2. #42
    Registered Member WagonCrazy's Avatar
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    Update:
    All of this back and forth on "ECU grounding" that makes the light/buzzer work when tripped" has been haunting me.
    So I went back thru it and confirmed a few things:

    1. Laszlo's schematic is CORRECT. This is how I have it wired...
    Inertia switch circuit.JPG

    2. I changed the electrical source from 12v Battery (always on) to 12v Switched (which only works with the key in the on position). Once I turn the key to OFF, the light/buzzer goes dead. (as I originally wanted).

    2. The polarity (wire connection points) on the LED light/buzzer DOES matter...I had it wired backwards the first time thru and couldn't get it to work (once the inertia switch was tripped).

    3. ECU Pin 09/Red CONTINUES to put out 12 volts AFTER the engine has stopped (either due to the inertia switch tripping OR just due to the engine dying and not running). It does NOT "go to ground once the engine dies" as I had stated in an earlier post. Disregard all mention of that please...

    4. When the inertia switch is tripped, it transfers the 12 volts AWAY FROM the fuel pump relay and INTO the LED light/buzzer, and makes noise (as long as the key is still in the on position). The fuel pump stops running immediately, and the engine dies within 2 seconds of the pump no longer running.

    Sorry for all the confusion on this.
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  3. #43
    Registered Member WagonCrazy's Avatar
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    And these are the items I used:

    Inertia Switch: $10 and no shipping. Ebay- https://www.ebay.com/itm/183727849647
    Inertia Switch.jpg

    There is no "3rd wire" in that harness plug, so you'll have to make one and install it yourself.

    LED Light/Buzzer: $6 and no shipping. Amazon prime https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    LEDlight-Buzzer.jpg
    Last edited by WagonCrazy; 01-30-2020 at 03:38 PM.
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

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