Kill switch accomplished - Fuel Economy, Hypermiling, EcoModding News and Forum

homeworkhome53 · 08-03-2008, 10:04 PM

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

MetroMPG · 08-03-2008, 10:50 PM

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.

homeworkhome53 · 08-04-2008, 07:50 AM

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

homewrokhome53

SVOboy · 08-04-2008, 01:06 PM

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

cfg83 · 08-04-2008, 04:20 PM

homeworkhome53 -

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

CarloSW2

getnpsi · 08-04-2008, 04:42 PM

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.

whokilledthejams · 08-04-2008, 08:45 PM

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.

bbjsw10 · 08-04-2008, 10:05 PM

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.

Kill switch how-to

ajax_6531 · 08-08-2008, 05:57 AM

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$$.

The Atomic Ass · 10-14-2008, 06:10 AM

Quote:

Originally Posted by ajax_6531

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?

getnpsi · 10-15-2008, 02:15 PM

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.

thefirebuilds · 10-17-2008, 11:35 PM

Quote:

Originally Posted by getnpsi

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.

bestmapman · 11-05-2008, 06:22 PM

Quote:

Originally Posted by homeworkhome53

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

Do you have any pictures of the fuze compartments.