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Thread: Engine Kill Switch/Button

  1. #1
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    Question Engine Kill Switch/Button

    Hello. I have a 1991 Mustang LX 5.0 with a 347 stroker SBF swap with the HP EFI system installed. I'm wondering if there is a way for me to intentionally stop the engine, while still keeping power to the computer? The only I have thought to do this, would be to use the I/O Harness to have a momentary switch trigger a 100 RPM fuel & spark cut rev limiter. If I'm thinking of this correctly, it should cut spark and fuel to all cylinders until it gets below the RPM limit, which is essentially what happens when I remove the key/cut power to the engine computer. With the rev limiter this low, it should be able to restart itself once it hits that low of an RPM. If I have missed something or if there's a better way to do this, I would love to hear about it, this is the best I have come up with so far. Thanks.
    347 SBF N/A hand built, 1991 Fox Body Mustang, rebuilt AOD, HP EFI 3.5" LCD display, 7" Digital Dash & both I/O Adapters. Dublin Ohio, 18 years old, built not bought.

  2. #2
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    Quote Originally Posted by paddyrk View Post
    I'm wondering if there is a way for me to intentionally stop the engine, while still keeping power to the computer? The only I have thought to do this, would be to use the I/O Harness to have a momentary switch trigger a 100 RPM fuel & spark cut rev limiter.
    If you're willing to install a switch, then you could simply connect it to the loose black ground wire routed to the system relay (terminal #85). Since it's a ground wire, you can ground on side of the switch, then only one wire needs to be routed to the loose black wire. This deactivates the relay, which cuts power to the the fuel pump, fuel injectors & ignition, depending on your ignition type. Look at the wiring schematics on figure 18, page 31: http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual - Section 13, Wiring Appendix)
    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.

  3. #3
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    Depending on the conditions you want the engine kill to work, you may want to look at the Safety Kill in the Boost configuration.

  4. #4
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    It's not an engine kill. Boost Safety Setup - Switched Trigger: When the "Cut Ignition" action is invoked, normal control will resume when the TPS<10 for 3 seconds, OR engine speed falls below 2500 RPM. http://documents.holley.com/techlibr...r10628rev3.pdf (Holley EFI Boost Control Instructions - Page 9)
    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.

  5. #5
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    Quote Originally Posted by paddyrk View Post
    With the rev limiter this low, it should be able to restart itself once it hits that low of an RPM.
    For however long this needs to occur, it will "restart itself" if this is a manual transmission, but won't if auto transmission. You would need to hit the starter again if auto transmission. Gary
    Regards, Gary

  6. #6
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    So just by grounding this wire, I'll be able to cut fuel & spark? Using a switch to complete the grounding of course.
    347 SBF N/A hand built, 1991 Fox Body Mustang, rebuilt AOD, HP EFI 3.5" LCD display, 7" Digital Dash & both I/O Adapters. Dublin Ohio, 18 years old, built not bought.

  7. #7
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    A key parameter is, does this vehicle have a manual transmission? Gary
    Regards, Gary

  8. #8
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    His signature states he has an AOD (Ford automatic overdrive transmission).
    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.

  9. #9
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    So now, the burning question is, how will the engine restart after the engine is cut, either by no crank signal, etc? Thoughts from Paddy please? Or do you want it to cut fuel in a "window" between idle speed and 100 RPM, and then as the engine is dying out, and it hits 100 RPM, it will start running again normally at this point? So you want a push button momentary that allows the start of the window to be enabled? Gary
    Last edited by Gaz64; 10-18-2019 at 05:49 AM.
    Regards, Gary

  10. #10
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    I'd like to be able to push a button/momentary switch that causes the engine to stop, and then after releasing that button, be able to turn the key forward to the cranking position for it to crank the engine and start it again. And yes, as Danny said, it's an automatic transmission.

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