Kill switch accomplished
 

I found a fuse in a box in the engine compartment marked fuel which I jumpered around with an inline fuse and switch which I mounted beside the manual gear shift. Works fine, but I can still hear my fuel pump running when in the off position, so I went back and looked some more and found a relay that is marked fuel pump in the same compartment. I think what I'm killing is the fuel injectors. When I throw the switch the car continues to run for a few moments. Just long enough to take it out of gear before it loses power. The instrument cluster continues to run and the odometer continues to total which is what I was looking for. The lights stay on which was a biggy for night driving.

homeworkhome53

Does it restart instantly? If you kill the fuel pump, it might have to repressurize before the car will start/run properly. Which could take a second or 2.

I interrupt my coil pickup signal from the distributor, and it still takes a heartbeat for the engine to stop running.

The restart is instant as long as you reset the switch to on.

homewrokhome53

Interesting. I really need to get a kill switch going on my car, thanks for the inspiration, :thumbup:

homeworkhome53 -

What SVOboy said. I gotta get my act together on this one.

CarloSW2

Is this kill for coasting or theft protection? It's a bad idea to kill the fuel pump. If you are in a dangerous situation it takes a few key cycles to get going again and it could kill you.

I agree that not killing the fuel pump is probably ideal, actually. The faster you can restart the car when the need arises, the better.

I need to get a kill (and starting) switch, too. I have a relay laying around, and wiring diagrams, I'm just not sure what kind of current I'd need to deal with as far as selecting my switches. I suspect that I'm not dealing with anything serious if I go through the ignition circuit, but I am having a hard time finding a straight answer. I'm getting more brave, within the context of limiting it to backroads, with my EOC'ing, but switches would make it simpler.

Here is a write up I did on a metro kill switch but should be able to make it work for a lot more cars. It works really well restarts as soon as I let off button and bump start or crank it over.

http://ecomodder.com/forum/showthrea...html#post50913

does anyone have the schematics to a jetski? Those have built in kill switches. You might find what they use to kill it would benefit us here. Of course, I could be talking out of my a$$.

Jetskis, (and motorcycles, and similar vehicles with kill switches built in to an FI system), have a safety loop, that when broken, stops the computer. On my Burgman in particular, this loop goes through the kill switch, side stand switch, and tip-over sensor.

Cars don't have this loop, so the same principles don't apply, unfortunately.

On this note, however, I'm looking at getting a Subaru Outback, anyone know how well their computers deal with having the injector power cut?

on cars ive installed kill switches and injector cuts, there is no stumble or funny acting. I think cutting spark or fuel happens so fast the computer doesnt "see it." This is different than let's say unplugging sensors, an injector or a spark plug. Doing this lets the engine still run poorly for many revolutions. The other sensors will detect erratic operation, and have time to trigger a check engine light, probably limp mode.

cycling the ignition key during EOC doesnt make the car act funny. installing a switch inline with a key isnt going to change much. I think we are reading way too much into it. i think the argument lies in cutting the fuel when the car is running not the spark.

cutting the ignition with awful radio shack relays can be dangerous considering the amount of amperage.

I have seen a few setups that cut the fuel pump and coil signal with two seperate relays, controlled by one push button switch. I have been thinking about this:

1. depress switch, relay 1 and 2 close, shutting off coil signal and fuel pump pressure.

2. release switch after a few seconds, relays open, allowing coil signal and fuel pump to refire. Fuel pump pressure will return almost immediately. Fuel is not burned or released as long as the engine is not spinning as the engine is closed at this point.

3. Bump start the car by releasing clutch. The vehicle will be off until this point, but the pump will pressurize as it is designed to during pre-ignition. The coil signal will begin firing as the engine rotates.

Do you have any pictures of the fuze compartments.

Howcome when I did this the fuel pump pressure did not return immediately to normal? Does this mean that it needs replacement already? Thanks.

some cars have a thing, i donno what it's called, but it's a fuel resevoir so the pump doesn't have to work as hard. This can go bad. It has a membrane in it that can rot out.

i have the schematics to my 08 aveo, i can locate a proper cut off point for a kill switch.

the problem with cutting off the fuel pump is that there is still fuel pressure in the lines. that gas will continue to be spat out as long as the injectors are still clicking and untill that line is clear. doing so adds a 2-3 second gap to "prime" the system to get fuel flowing at a proper pressure to get the engine going. too much time wasted with how fast paced life is.

cutting off the injectors is the best idea since no fuel can flow without them having power. but the problem with that is that the ECM (engine control module) is controlling the ground on the injectors. on an OBD-II system, the injectors are being controlled individually at low RPMs. there should be a fuse for the power wires to the injectors. that would be the right point to cut power on/off. not the fuel pump fuse or relay.

my alldayadiy account expired, so i cant look up the schematics till i renew the account. but having a cutoff at a fuse listed as INJ would be the right way to go at this.

this is the fuse you want to cut power off to.
http://i47.tinypic.com/x6dcb8.jpg

cutting off power to the fuse labled FUEL is bad juju. thats the same as cutting power off to the fuel pump relay. its all bad juju.

Suggestion: Instead of just cutting off or shorting the injectors, wire them up like a "true bypass" guitar effect pedal. DPDT toggle switch and some resistors that are the same Ohm rating as your current ones will work. I have mine set up to kill 2 out of 4 cylinders on my car.

Switch layout will be like this:

--1 --4
---2 ---5
--3 --6

2&5 are center taps. Rewire the injector (+) wire to these. Lets go with one side for now, then wire the second one up. Wire the (+) wire on say injector 3 to pin 2 on the DPDT switch. Run pin 1 back to where the cut wire left off. For pin 3, solder a resistor that matches the injector's Ohm rating in series and have that go into a T splice into the (-) injector lead. Repeat for side two, or hook do the same thing on a DPDT relay and have two of them, then have a momentary pushbutton switch to activate the relays. Viola!

That way the ECU won't freak out, although if you only shut off two cylinders, avoid high rpm. A: It shakes horribly, B: It WILL trip off the ECU, and the Check engine light is baaaad. And as far as I know, something like this should work on just about any Honda, although it'll need to be tweaked with for some I think. Should probably work on other vehicles too.

does it work
 

Does it work? dont we need to worry about starting the car up again while coasting in a gear vs Neutral and starting it then?

tf4624 -

americasfuture2k can "bump start" the car from neutral after he has killed the injectors. If he never puts the car in neutral and restores power to the injectors, it will start right up again. This already exists in cars as DFCO (Deceleration Fuel Cut-Off).

CarloSW2

As long as the car is in mothion and the drive wheels and when transmission is in gear it can get the engine internals rotating again. as long as power is active in the computer, ICM, and coils the engine will fire up again when fuel is applied. From a dead stop the engines rotating mass internals will need assistance in spinning again. I.E. Using the starter.

On the turning off of individual cylinders, I wouldn't recommend it without a bit more thought.

On a fuel injection engine, the o2 sensor is designed to tell the ECUr if the engine is running lean. By cutting fuel to some of the cylinders, you are introducing a ton of o2. When that happens, the ECU decides it is running too lean and dumps gas into the cylinders. So much gas goes in that the cylinders walls can get washed, and gas goes into the oil. Why do I know this? I had a setup on my Explorer to shut off half the cylinders. Nice thing about it was it shut off one side of the engine and it was still balanced; ie no vibration. But my oil level slowly rose unexplicably until I figured out it was the excess gas. ( Funny thing was we were able to increase gas mileage 25% using this method.)

Long story short, the engine ended up slowly dying on us and finally quit altogether. I'm planning on trying this again, but instead I'll split the intake and exhaust in 2, or figure out a way to halve the signals coming from the MAP sensor and O2 sensor so that the computer doesn't detect a lean condition.

Anyone here know how to do that?

any update on this?

@shadetree one idea to fool a computer with a V6 or V8 engine would to relocate the o2 sensor(s) into a stream that isnt being "tampered" with. This would involve pretty much designing a long tube header system for the explorer and letting the sensor sniff cylinders that are still operating in a range it likes. A really nice exhaust system would probably get you some gains just by that on the highway. The cheap way would to weld another o2 bung on just one side and run a longer oem sensor so they are both reading the same bank. However on paper it has its merits and downfalls. If you want to shut off cylinders when you want I think it would be a good idea to "rotate" them so there is no washing down and extra wear, so that kinda taxes the o2 moving idea too.