Kill switch wiring

If you break the neg side and break the fuel pump ground wire at the same time, the car shuts off, fuel flow stops , and the whole wire system has better crash resistance. Smashing the ground wire into bodywork wont start a fire. This also avoids the big hassle of the alt contining to run the car.
The Bosch alt are often self exciting/ firing at around 3200=4000rpm . Check yours. Most will start without a light/exciter wire. For the few that need a light , I use two side marker light sockets and bulbs. The diode is in the alt , glowing the bulbs, key on engine off. When the car/alt fires, the lights go out.
I use this method for the ministock that needs to make a vacuuum rule. I need the alt load to increase the vacuuum so that I can use more cam.
I use two bulbs, because if one burns out the alt will not fire and the car wont make vac, costing me a DQ and money..
FWIW, many race cars have the starter power bypassing the bat break. The break switch does not like the high amps for very long and often results in a no start on the grid with 2 to go.
I dont condone this wiring, but my endurance car has the bat switch that can be bypassed really quickly.
HTH, MM
 
keilysmith said:
It can be as easy as simply adding a little child and a transient (normally open) switch. Look for the sign "hot" exhaust - is a cable that goes from the center of the leg volume control, and ends at the end "tab on the outlet. Now, add a cable, for example, during the volume control, and welding of this cable to switch (either legs up). Then another wire bond for the remaining leg (the two who want to use) the switch and solder the other end to ground.
Click to expand...


kielysmith = [ame]http://www.youtube.com/watch?v=G6D1YI-41ao[/ame]
 
As long as we're sullying the topic...I'll match your Hungarian with a Turbo Encabulator...

[ame]http://www.youtube.com/watch?v=rLDgQg6bq7o[/ame]

...and raise you a Retro Encabulator.

[ame]http://www.youtube.com/watch?v=RXJKdh1KZ0w[/ame]

(it's funny as hell when John and I think of the same things... ;) )
 
try looking at how i wired my 86ish honda crx.

http://www.flickr.com/photos/tom91ita/sets/72157603191663037/

basically, i tried to show on the car's wiring diagram and the switch wiring diagram how they relate to each other.

so connection "A" or "D" on the switch is shown as "A" or "D" on the wiring diagram.

hope this helps. btw, i have done the annual tests as well race weekend tests and never hurt the alternator. (weekend tests are wondering why the car won't start when i arrive at the track and then remembering i keep the master switch off in the trailer......)
 
Posting for a friend that is prepping his car for SCCA in NARRC ITE..

We're trying to wire the killswitch. He has a late 1.8T VW motor in a 84 Scriocco.

"The problem with the altenator is that it takes it's feed for the exciter wire directly from the battery cable wire from the back of the car. I will asssume I have to cut all power to the main feed cable before the altenator? Not sure how to isolate it completely from the system so the car shuts off when switched."
 
How "late" of a VW 1.8t?

Most VWs use Bosch alternators with internal field circuitry; ergo not even with the sheisrocket would there be a field wire to bisect. In that case, I'd recommend bisecting the wire from the battery to the starter with the main cut off circuit, then bisecting the main ignition wire through the secondary normally open circuit of the switch ("Z or 2" in the diagram on page one.)

For the 1984 Scirocco, the secondary wire to bisect would be the "15" or "switch on" circuit that supplies power to the rest of the car, a 16-gauge black wire coming off the ignition switch. Cut that wire and the car dies.

GA
 
I encountered similar situation on my '87 VW GTI 16V when wiring the kill switch. Alternator keeps the engine running quite fine when battery power is cut..... So I plan on interrupting the "T15" to the ignition because that will kill the spark which will in turn kill the fuel pump. Most vehicles should have some kind of fuel pump enable that's controlled by the ignition. So when the engine stops running the fuel pump stops pumping, no need for a separate fuel pump cut. This should also dissipate the charge from the alternator so there is no risk of blowing the regulator with a sudden shutoff of the alternator output.
 
kill switch insanity

This is a subject that is a real pain to me. Yet another vaguely written rule in the GCR that is subject to interpretation.

I have always wired my switches to kill battery power and the fuel pump. Cars will run just with just a battery or an alternator but if you take away the fuel I guarantee the engine is going to die. Sure, it takes a few seconds for the engine to shut off and the alternator to lose it's energy but at that point in time ALL circuits are dead and there are no fuel lines pressurized to 60-90 psi just waiting to burn through or crack and cause a flash fire. Fuel pressure is gone because the engine burned it off. Certainly a much safer scenario for the turn worker who is trying to assist you or put out an underhood oil/gas fire.

Why is the rule poorly written? There are no criteria for time, testing, or wiring for most cars. The fact that the GCR is specific about wiring a SRF but not any other vehicle leads me to believe there are options as to how the results are accomplished. The way I wire my car has all circuits dead with the car running after a few seconds and the circuits are all dead with the car not running. Given that the rule simply states that all circuits must be cut would mean that my wiring accomplishes that goal.
 
best first post ever?

dhrmx5 said:
This is a subject that is a real pain to me. Yet another vaguely written rule in the GCR that is subject to interpretation.

I have always wired my switches to kill battery power and the fuel pump. Cars will run just with just a battery or an alternator but if you take away the fuel I guarantee the engine is going to die. Sure, it takes a few seconds for the engine to shut off and the alternator to lose it's energy but at that point in time ALL circuits are dead and there are no fuel lines pressurized to 60-90 psi just waiting to burn through or crack and cause a flash fire. Fuel pressure is gone because the engine burned it off. Certainly a much safer scenario for the turn worker who is trying to assist you or put out an underhood oil/gas fire.

Why is the rule poorly written? There are no criteria for time, testing, or wiring for most cars. The fact that the GCR is specific about wiring a SRF but not any other vehicle leads me to believe there are options as to how the results are accomplished. The way I wire my car has all circuits dead with the car running after a few seconds and the circuits are all dead with the car not running. Given that the rule simply states that all circuits must be cut would mean that my wiring accomplishes that goal.
Click to expand...
 
Don't overthink it; it's all about safety.

Think of it this way: what if you were upside down in a Miata and the damn thing caught on fire, still running thus the alternator still juicing, and it was porking out fuel from a ruptured fuel line; what would YOU think about "just a few seconds" of additional chassis electricity after hitting the kill switch?

After all, what's "just a few seconds" of ruptured fuel line between friends?

That's the kind of stuff I think of when I'm tech'ing a car. If I tested your kill switch and it continued to run "just a few seconds" after I hit the switch, I'm dingin' ya, plain and simple. You can argue all the technicalities you want - and you'd be right, from a purely technical standpoint - but when you hit the kill switch the engine should stop, right then and there, with no power to anything at all, no delay, no dwell time, and certainly not within a few seconds.

And that's really the way it should be.

And when it comes down to it, how is splicing into the alternator field circuit wire (or the ignition circuit wire) any more difficult than splicing into the fuel pump wire? Just do it "correctly" and everyone's happy, yes? - GA
 
Last edited:
I wire all of the new builds to cut the fuel pump power. The modern car has so many relays, field wires, diodes, etc.
The only sure way to stop the fuel fire( and that is the reason for the power switch),is to drop the power to the fuel pump.
Remember Greg, AT idle the stop may be 2sec, at RPM the stop is right now.
Never had any issues at tech. Actually they like my cars, cuz they shut off.
MM
pS the VW does not need a field wire.. Most ,if not all, will self field @ about 3500rpm, engine speed.
 
As long as the alternator self-energises any thing, all circuits are not dead. I ground out the ecu key wire, the alternator field wire, and the fuel pump wire, with a immobilizer relay. Imagine that, I use a relay that's already in the wiring, and on the car.

The rule flexibility is because not every car has a coil wire, or it may be a fuel cut-off valve on a carburetor, or in my case it's the ecu wire. Some cars didn't come from the factory with an immobilizer relay, but they're easy to get from your local alarm/sterio shop.
 
Quick and dirty method:
wire the alternator output to the battery side of the cutoff switch. no need to fiddle with field wires, ECUs, fuel pump relays, nothing.

when you flip the switch, there is ZERO power anywhere under the hood. Zip. Zilch. Nada. No fuel pump, no ignition, no ECU. Absolutely foolproof and there's no freewheeling alternator feeding back into the circuit to fry the ECU.

Even if the alternator is self-fielding, all it's doing is charging the battery that is already disconnected. Took me about 6' of #8 wire and 30 min to accomplish the job.
 
Matt93SE said:
Quick and dirty method:
wire the alternator output to the battery side of the cutoff switch. no need to fiddle with field wires, ECUs, fuel pump relays, nothing.

when you flip the switch, there is ZERO power anywhere under the hood. Zip. Zilch. Nada.
Click to expand...

Uhh ... except for that big wire going to the alternator ... Doesn't cut "all circuits."
 
JoshS said:
Uhh ... except for that big wire going to the alternator ... Doesn't cut "all circuits."
Click to expand...
since the field coils on the alternator are cut, it effectively cuts "all circuits". All sources of power are on one side of the switch, all users of power are on the other. You flip the switch and the car stops. right now. What else do you want?
 
Matt93SE said:
since the field coils on the alternator are cut, it effectively cuts "all circuits". All sources of power are on one side of the switch, all users of power are on the other. You flip the switch and the car stops. right now. What else do you want?
Click to expand...

Maybe that's good enough, and as I think about it, maybe I'm colored by the fact that my car has its battery in the back. I was trying to avoid having any electricity in the engine compartment. But I suppose if the battery is in the engine compartment, that's not a realistic goal.

But it says "all circuits" and as long as there's a circuit from the battery to the alternator, to the engine ground, back to the battery, it's hard to argue that it meets the letter of the rule.
 
My battery is in the trunk as well. the only wire that's hot going into the engine compartment is the short wire going to the alternator. If you're in a wreck big enough to rip the alternator off its mount or break the engine loose, then a little #8 cable is the least of your worries.
As for cutting all circuits, I would implore you to argue that one to tech. this method cuts anything and everything that uses power or could keep the engine running. there is ONE wire going into the engine bay that's still got juice on it, and it's not going anywhere that's going to keep the car running. That's the intent of the rule, is it not?
 
Kill Switch Question

Well silly me waited until the week of the ARRC to figure out my kill switch, I THOUGHT it was going to be easy but underestimated it. I made a switch panel a while back from my ignition switch and thought I could combine that wiring (the switch that kills pump and what not) to my battery kill switch and be golden, sadly I was wrong.

I have a two terminal switch. I see people use ones with 4 and 6 sometimes, so is there anyway to do it with just two?

If I wire my hot alternator wire directly to my battery then run that cable to one side of the switch and run the other side of the switch back to the alternator and + battery terminal in the fuse box would that kill it?

At least everything else is ready. :p
 
simon, that sounds what I've done with mine. you also want to run a wire from the switched side to your starter if that's not part of the fuse box wiring. IIRC mine went straight to the battery (originally about 3' away from the starter), so when I installed my switch, I ran a dedicated wire there too.
Works every time. :)
 
You must log in or register to reply here.
Back
Top