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Thread: anyone use a fuel pump kill switch?

  1. #1
    Registered Member WagonCrazy's Avatar
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    anyone use a fuel pump kill switch?

    Considering adding in this $20 item to the electronic fuel pump circuit in my restomod Nomad build...specifically to kill the power to the fuel pump relay in the event of a hard crash, rollover, etc.

    As its wired now, if I had an accident that resulted in a break of the fuel line anywhere between the tank and the engine, (with the 12v power still on because the key is on)...I'd be shooting fuel out at the rate of about 50 pounds of pressure. Instant fire I think...

    Do any of you guys run something like this item to kill the power to the intank pump and stop it from becoming a flamethrower?

    https://www.amazon.com/Hotwin-Inerti...YBVFV2CRV0Y0B0
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  2. #2
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    WagonCrazy:

    I am admittedly the biggest Ron Francis fanboy in existence. They always have a solution and their parts are top notch.

    Here is their electric fuel pump cutoff:

    https://www.ronfrancis.com/prodinfo.asp?number=CR%2D92

    Its Part Number CR-92.

    Its a collision cutoff.

    The less expensive way is to use an Oil pressure switch to complete the ground. Once oil pressure dies it effectively kills the pump.

    Its not cheap but their stuff is so damn nice.....

  3. #3
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    That kind of switch is of no or little value for an EFI setup since the ecu is going to shut off the pump as soon as the engine isn't running, and an EFI engine won't run long with no fuel pressure. It makes more sense on a carb deal because there isn't anything to shut it off with that system.

  4. #4
    Registered Member 55 Rescue Dog's Avatar
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    It seems like it could be tied into a remote battery-disconnect latching solenoid, and that would kill the whole electrical system if something bad happened. The same solenoid could be also used for a remote disconnect, simply operated by a toggle switch. It would be a good setup even without the crash sensor. That's the disconnect I'm going to use in my car anyway. Can easily find a great place for a toggle/pushbutton switch, instead of trying to route battery cables for easy access to the disconnect. I will also try and do all of the switching/connections on the negative side, to minimize accidental contact points you have using the +plus side. I would also want a small pilot light to know when the system is powered up, since they use a momentary switch on a latching relay, with no indication. Pretty easy system to turn on/off, but also would be easy to accidently power up, especially if using the supplied 2-way momentary toggle switch. I will try and find a more fail-safe solution in addition, like when working on the car for example, which could as easy as just pulling off the negative cable like I've always done, or should have.
    https://www.ronfrancis.com/prodinfo.asp?number=MS%2D21
    Last edited by 55 Rescue Dog; 12-14-2019 at 03:29 PM.

  5. #5
    Registered Member 55 Rescue Dog's Avatar
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    I really like the products that Ron Francis wiring sells. They are not cheap, and the shipping prices are based on cost, instead of weight just to add to the pain of getting what you pay for, to get good stuff. The wiring harnesses do give you the option of wiring from either direction to the device, which I've found to be a plus too, instead of running all of the wires from one common point from the fuse panel.

  6. #6
    Registered Member chevynut's Avatar
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    It's so worthless that Fords, Lincolns, Jaguars, and other cars had them for years. I think it's a good idea to incorporate some kind of safety fuel shutoff that doesn't depend on the engine dying to shut off the fuel. If the fuel return line is broken in an accident, the pump could continue to run until the tank is empty. Even a cracked pressure line could spew fuel and the engine could still be left running. Most new cars use the airbag sensor circuitry to stop the fuel pump in the case of an accident. I have an inertia switch from a Jag but it says Ford on it. IMO it doesn't hurt a thing, is simple and inexpensive, and may save your car or your life.

    https://rts.i-car.com/collision-repa...switch-go.html
    56 Nomad, Ramjet 502, Viper 6-speed T56, C4 Corvette front and rear suspension

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  7. #7
    Registered Member WagonCrazy's Avatar
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    the inertia switch, it is designed to shutoff the fuel pump in the event of a collision, as to not create a fire hazard if a fuel line is damaged. Inertia from a crash was used to trigger the switch. This worked good for a collision, but the switch would sometimes trigger after hitting a large enough bump, leaving a driver stranded on the side of the road.
    So thinking this thru...I should install the switch somewhere where I can get to it fairly quickly, in case I have to manually reset it. I wonder how sensitive these $20 Amazon switches are to road bumps? I would hate to have this thing shutting the pump down in a non hazardous situation. Guess I'll just wire it in at the center console (where the fuel pump relay and fuse is) and take my chances...
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  8. #8
    Registered Member WagonCrazy's Avatar
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    That kind of switch is of no or little value for an EFI setup since the ecu is going to shut off the pump as soon as the engine isn't running, and an EFI engine won't run long with no fuel pressure. It makes more sense on a carb deal because there isn't anything to shut it off with that system.
    Huh?

    Running or not, when the key is turned to the first position...the ecu sends the 12v signal to the fuel pump relay, which allows 12 volts to got to the pump, which makes it run.
    Running or not, as long as the key is in that position, the relay is on, and the pump is pushing 50# of pressure from the back of the car (tank) to the front of car (fuel rail on the LS engine).
    If at any point between them...a physical break in the fuel line occurs...the fuel would continue to pump and fire hazard occurs.
    Running or not.
    As long as the key is in that first (run) position...
    Last edited by WagonCrazy; 12-16-2019 at 07:59 AM.
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  9. #9
    Registered Member WagonCrazy's Avatar
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    So I just ordered one from ebay.. $10 and change (delivered)...

    https://www.ebay.com/i/183727849647?...yABEgKu8fD_BwE

    I'll wire it up and bench test it before I install it....as I want to know how much inertia it can take before it triggers. Gonna be somewhat unscientific though...as I will whack it with a screwdriver handle, whip it around in the air by its wires, smack it on the bench, etc.
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  10. #10
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    Running or not, when the key is turned to the first position...the ecu sends the 12v signal to the fuel pump relay, which allows 12 volts to got to the pump, which makes it run.
    Running or not, as long as the key is in that position, the relay is on, and the pump is pushing 50# of pressure from the back of the car (tank) to the front of car (fuel rail on the LS engine).
    No. When you first turn the key on, the pump is on and "primes" for a couple of seconds. It then shuts off. It turns on again when an rpm signal is detected from the ignition sensors. If the ignition sensors don't show rpm, the pump is shut off.

    The only real question here is how long can an EFI engine run without fuel pressure. Not long at all.

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