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Thread: Fuel Pump Kill Switch

  1. #1

    Default Fuel Pump Kill Switch

    I'm running a billet inline fuel pump and I was wondering if I can put a kill switch inline (green wire from the harness). To shut the pump off when I just want to turn the key for power, and not have the pump running away. Or would it have to be on the ground side of the pump?

  2. #2
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    It doesn't matter, as long as the switch is rated to handle the amp draw of your pump...
    Best to find a switch that is rated to more amperage than the fuel pump fuse.
    So that the fuse remains as a fuse and the switch doesn't become the fuse if it's too small.

  3. #3
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    Quote Originally Posted by ssenay72 View Post
    To shut the pump off when I just want to turn the key for power, and not have the pump running away.
    The fuel pump isn't supposed to run continuously with the key-on/engine-off.
    The Fuel Pump Prime (in Engine Parameters) runs it for 5 seconds, then it's off.

    S2H gave you good kill switch amperage capacity advice.
    Some people prefer a kill switch on the ground side; if the wiring is damaged, it won't be a short circuit.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  4. #4

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    You should not be trying to kill the pump directly anyhow. The pump should have a relay...put the switch in the control line. I might ask "why" do you want the key on with engine off? Depending on your alternator setup this can cause field current draw and maybe even damage to the brushes, and some ignition systems draw current with key on, that is, heat up the coil.

    If you HIDE this switch and don't label it, this also makes a great anti theft device.

  5. #5
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    Quote Originally Posted by 440roadrunner View Post
    I might ask "why" do you want the key on with engine off?
    I don't think he's referring to key-on/engine-off as a long term thing.
    Just temporarily, as he performs checks, reviews data and makes ECU programming changes.
    If using a 2nd dedicated fuel pump relay (Link), I agree it's more practical to kill the pump relay trigger wire.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  6. #6

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    Yeah, I have a relay I could put in, I didn't because it seemed the Terminator harness already had one installed (more or less). I can just hook that up I suppose. I guess the only other reason for a kill switch (hidden) would be anti-theft. But I primarily would like to cycle the key for data review and programming basically.

  7. #7
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    Again, I don't think all this is necessary because:
    The fuel pump isn't supposed to run continuously with the key-on/engine-off.
    The Fuel Pump Prime (in Engine Parameters) runs it for 5 seconds, then it's off.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  8. #8

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    I haven't programmed anything at all yet, so would it be something I have to set first before it works? Or should it work automatically? Working with the handheld at the moment, will probably switch to laptop eventually.

  9. #9
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    I routinely tell my fuel pump to prime for zero seconds, so I can key forward and test certain circuits. This doesn't provide any anti-theft benefits, but it does kill the pump in key on/engine off situations.
    93 Notchback, 383ci SBF, Highports, 80mm turbo, custom cam, TH400

  10. #10
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    Quote Originally Posted by ssenay72 View Post
    I haven't programmed anything at all yet, so would it be something I have to set first before it works? Or should it work automatically?
    Quote Originally Posted by Rick90lx View Post
    I routinely tell my fuel pump to prime for zero seconds, so I can key forward and test certain circuits.
    Again, the default "Fuel Pump Prime" time is 5 seconds (with any base calibration). It's automatically entered for you.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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