Here’s an interesting electrical question/poll.

[trularin]

It does not matter what type of fuel pump you have.

The engine will stop running if the switch is turned off ( providing it is wired correctly ). Some engines have problems running up-side-down as it is.

If gas is leaking, nothing short of absorant material is going to stop that.

[RallySnake]

The BIG problem is the BIG wire that has to carry all the current from the alternator to all the circuits of the car and to the battery to charge it. You cannot cut that off without a massive (and totally impractical) relay.

You have to focus on cutting power to the ignition system and fuel pumps (if they are electric). It does not matter if you do that on the hot side or the ground side. It is important that both the emergency cutoff switch and the inertia switch break the connection to both of these circuits. Once you cut ignition, the engine will stop and the alternator will make no more power. Then, there is very little danger of a spark igniting all that spilt fuel.

If you don't have an inertia switch, you can get one out of a junkyard Mustang for almost nothing. Odds are, it has only been used once!

RallySnake

[Blas]

The seneraio described below was just to set the sceen, the important part was understanding the limitations of the cut-off switch due to the way it is installed on your car. Heck, I make the custom wiring diagrams and I never really analyzed how the cut-off switch operated beyond knowing that it isolates the power so you could work on the wiring safely. Had no real reason to look at the installation that closely...
And I agree that making the system work properly would require some fancy wiring, especially with an AMP meter installed in the dash and battery installed in the back...Even the red plastic key won't pass NHRA inspection..
Food for thought...
How many people have an inertia switch installed? Ever any problems with it under hard acceleration or deceleration? Maybe a new addition for the wiring diagrams...Maybe someone has a photo of their inertia switch installation handy?

[Pete Munroe]

I have a "inertia" activated switch mounted on the chassis upright just in front of the drivers door.

Wired it to shut off the power to the Holley electric pump in the left rear wheel well. Activated by impact ( inversion also I think). They must be mounted to something solid, like the frame...not something that can move and absorb impact before the switch gets tripped.

Installed it where I could reach to reset it (push a button on the top) as I had no idea how sensitive it would be in the car. It has never tripped. ( has been installed for 13000 miles and 10 or more track events).

This switch is from Pegasus Auto Racing Supplies, part #1108 about $65~. It comes with electrical plug, wiring, terminals and bracket.

You can get them for much less money, but then you have to have the "plug" to finish the wiring. Almost got a Ford Tempo switch for like $15? and then realized I couldn't easily get the electrical plug as it is part of the wiring harness in the car. If you took one out of a junkyard car you would have the plug I guess.

My "main kill switch" shuts off EVERYTHING. Nothing stays as a "hot" circuit.

The main-kill switch is behind the passenger seat. Good for security, not so good for the track.

Pete