Interupting my Crankshaft position sensor didn't kill it
 

So a couple weeks ago I spent $10 for 3 days of access to the Honda/Acura Tech manual website so I could print off the wiring diagrams for the Crankshaft Position Sensor under the dash. It took me a while to get around to it, but tonight I finally got around to wiring in my normally closed momentary open switch and it doesn't work. Or it does interrupt the signal, but the computer overrides it or something.

What happens is when I push the switch it almost stalls, then recovers. If it push it again, it does the same thing unless I push and hold it, in which case it almost stalls, but recovers and then if I push it again, it doesn't even hesitate. Not sure what is going on, but it's not working as a kill switch like it should. Any thoughts?

My only thought is that it uses several signals to determine a stall and if the Camshaft sensors are still providing a signal, it must override the crankshaft sensor. Just a guess.

interrupt positive supply to the injectors
 

That's probably true. Have you tried unplugging both the crankshaft and the camshaft sensors at the same time? Does the engine start with the crankshaft sensor unplugged? Does pulling only the camshaft sensor kill the engine? In modern engines the ECU syncronises those two sensors at startup, so one can take over if the over fails. In my case the engine doesn't start without a signal from the camshaft sensor, but will work without a hiccup if I unplug it once the engine is turning. Pulling the crankshaft sensor does kill my engine, however.

The problem with crank/cam sensors is its used for ignition firing and timing and you want spark to always work.
Plus its got to make the ECU throw codes and possible limp mode ,you don't want that .

As mwebb mentions ,the right way is interrupt injectors 12v power side .

I originally tried interrupting the cam and crank position sensors on my car, but they did not kill the engine either. Then I tried interrupting the ignition circuit, and that killed it, but it had unburnt fuel left over and on restart, it caused a SES light due to wacked out O2 sensor readings when the fuel hit the CAT. You could actually hear the rumble in the exhaust of the burning fuel. Finally I switched the common 12v supply to the injectors, and have been working (killing) great for over 2 years. :thumbup:

Sounds like I'll have to change my point of attack to the fuel injections system. I sure hope that was one of the schematics I downloaded. Ten bucks for three days of access to the manual is rediculous... especially twice.

I think ideally you want both ignition and fuel to shut off. This is what happens when you key off too. Leaving one running without the other creates other issues.

My tbi metro stumbled on if I only killed fuel. There was a lead from the distributor (camshaft sensor) that would cleanly kill ignition and fuel and not throw codes when that circuit was opened (with a nc microswitch on the shifter)

even my 97 saturn mpfi would stumble on and accidentally relight occasionally if only killing fuel. Here putting the nc microswitch in series with the crankshaft sensor worked perfectly, w/no codes.

My tdi golf needs the solenoid on the pump to be interrupted with a more substantial switch.

I think we need a database ( a page in the wiki) of car models and proven effective kill switch approaches. Because if you only have to interrupt a signal level circuit, that is as trivial to do as it gets, whereas if you need to interrupt inductive loads (coil & injectors) then you might have to add a relay or two if you want nice tactile push button control over it.

I second this:thumbup:
There should also be a section for known issues for each kill method. For example, doing this-and-this works, but throws code number #...

It depends what you want , if you still have engine turning with this kill switch you definitely want fuel injectors off and spark on . If you want a dead kill then just kill power to whole ECU with the PGM-FI power relay .
Which is basically same thing as turning key off .
On honda/Acura it will kill power to the injectors , fuel pump and ECU , just need wiring diagram .