Kill switch how-to

[bbjsw10]

I installed an EOC switch today. Here is how I did it, should work on any 89-94 as far as I know.

Supplies needed:
1. momentary switch normally open
2. relay use a good one like Bosch 5 pole 30Amp
3. inline fuse holder capable of 20 amps
4. 15 amp fuse for holder
5. 16 gauge wire use no smaller than this or will over heat
6. ring terminal for grounding momentary switch
7. nylon ties
8. wire loom
9. (2) 1/4" male spade connectors for 16 gauge wire
10. (4) 1/4" female spade connectors used to connect wires to relay
11. Solder and soldering gun a must for underhood wires. Don't want to break down because of bad connections, Do you?

Begin by disconnecting battery. Pull 15 amp injector fuse in under hood fuse panel. Cut 2 sections of wire roughly 6 feet in length. Solder a spade connector onto fuse holder, and one section of above wire to other side of holder, mark this wire with a piece of tape at end. Solder another spade onto second wire used as return from relay. Run these 2 wires into underdash to mount relay. You will need the momentary switch grounded on one side, this will be to trigger relay. The other side of switch goes to relay. Diagram below. Mount your switch wherever it is easy to get to, I used my shifter knob. Once you have all connections made plug the fused wire into fuse panel and the unfused wire in as well. Pic below. Reconnect battery. Install fuse, match the size it calls for 15 Amp on my car. Start car, verify it runs. Press button verify it dies out.

To use while coasting shift to neutral for coast, hit button. Enjoy. Bump start vehicle, no key needed. Just release button, ease out in clutch in a higher gear, do not pop clutch, but do not overly slip either. Takes practice but saves alot of fuel. Questions just ask.

Edit: 85 and 86 are reversed on my diagram. These pins are the control side and reversible. One ground, One power. Makes no difference on the position of these 2.

[dcb]

That's a nice writeup bbjsw10,

I had an injector kill switch on a metro, problem was it wouldn't shut off cleanly. I switched to the camshaft pickup trick (disables ignition) and it is a much cleaner transition to off and restarting, and maybe I can reuse that fuel on relight . You could kill both too with the right combination of relays, that would be more like what happens when the key is turned off.

[bbjsw10]

Originally Posted by dcb

That's a nice writeup bbjsw10,

I switched to the camshaft pickup trick (disables ignition) You could kill both too with the right combination of relays

Thanks

This camshaft pickup you are talking about what is it and where? Would my 91 have it? I have been wanting to do something like this and make my switch control both relays at same time.
EDIT: I looked in service manual, has camshaft position sensor with 2 wires a ign. ref. in and ign. ref. high would these be what you are talking about? Couldn't I just use a second relay to kill power to coil?

[dcb]

I think those are the right wires, coming out the side of the distributor. I tried the coil lead, but the current still found a path through the relay, oops, LOL

Note, you can interrupt either wire. In my rig the connections are currently exposed (I'm lazy in some ways) and the engine won't die when it rains with the kill switch

[cfg83]

bbjsw10 -

Thanks! I'm gonna save this post for careful study.

CarloSW2

[Raysp30]

What's the ideal way to cut the engine off using a switch?

It seems like a lot of people are opting for the Injector switch. I read a very easy DIY post that cuts into the fuel pump wire to act as a theft deterrent. Would this also work?

[bbjsw10]

Originally Posted by Raysp30

What's the ideal way to cut the engine off using a switch?

It seems like a lot of people are opting for the Injector switch. I read a very easy DIY post that cuts into the fuel pump wire to act as a theft deterrent. Would this also work?

I use my to do EOC. That is whenever I have a chance to coast I use it to "kill" engine, then bump start in 5th gear at speeds as low as 5mph.

I don't like the idea of shutting off fuel pump to kill engine. The injector is designed for that pressure. Would work awesome for theft deterrent.

[MechEngVT]

If an injector kill doesn't shut off the engine quickly or cleanly it's either not completely killing the injectors or your injectors are leaky.

I would hesitate to use an ignition-only kill on an EFI car because that means your injectors will be spraying fuel through multiple crank revolutions with no ignition to burn it up. This can cause oil dilution, scoring of the cylinder walls, and wasted fuel. Even golf carts use a fuel shut off to kill the engine because the ignition ground causes the fuel/oil issues. Of course you could use BOTH an injector and ignition kill (like the key switch)...that would do the trick.

[bbjsw10]

Originally Posted by MechEngVT

If an injector kill doesn't shut off the engine quickly or cleanly it's either not completely killing the injectors or your injectors are leaky.

I would hesitate to use an ignition-only kill on an EFI car because that means your injectors will be spraying fuel through multiple crank revolutions with no ignition to burn it up. This can cause oil dilution, scoring of the cylinder walls, and wasted fuel. Even golf carts use a fuel shut off to kill the engine because the ignition ground causes the fuel/oil issues. Of course you could use BOTH an injector and ignition kill (like the key switch)...that would do the trick.

These are the reasons why I did an injector kill instead of ignition kill. I don't like the idea of unburnt gas sitting there. This how-to is on injector kill, that way the fuel gets burnt up then engine dies, no oil getting in oil or burning. FIRE BAD!!

[dcb]

It isn't that the injectors are leaky, it is that there is a layer of fuel on the inside of the intake manifold, it is a normal state of affairs.

That fuel is absolutely not usable if you "dry out" the manifold every time you kill the engine as the mixture is so far off there is no real useable power in it, and it causes the engine to stumble to a halt and it frequently relights when you didn't mean it to.


If you turn off the ignition, the engine shuts down right away. That fuel doesn't really go anywhere anytime soon if the throttle is closed and the engine isn't turning, so it is still there waiting for use when you restart the engine.

I do not know that oil dilution is much of a concern, I know planes would add fuel to the oil just prior to shutdown in winter and it would evaporate out when the engine is up to temp, and I don't know that much, if any, fuel is actually getting into the oil from sitting in the manifold between pulses.

[MechEngVT]

dcb;

In multi-port fuel injected engines there is not a substantial amount of fuel sitting in the manifold. Port fuel injectors spray into the intake port onto the closed intake valve. The only way for this fuel to get into the manifold would be as it evaporates and then exhaust reverts out the intake valve at initial intake valve opening it may push some fuel vapor up the intake runner, but then the piston will draw this vapor back down the runner into the cylinder as the cylinder fills.

When an engine shuts down it doesn't instantly stop. It spins down to a stop over time as engines have substantial rotational inertia. When I EOC my truck I have to key-off for almost 2 seconds (from 2000 rpm or below) because after just 1 second if I key back on the engine still has enough speed to restart itself. At just 1000 rpm an engine rotates more than 16 times in one second meaning that each cylinder goes through at least 8 intake cycles. If you kill your ignition but not your fuel injection you will be injecting enough fuel onto your intake valve to be sucked into the cylinder for about 8 combustion cycles per cylinder that will not be burned before the engine stops. This fuel will wash oil off the cylinder walls, dilute the oil, and some of it will go out the exhaust as unburned HC and/or will collect in the catalytic converter where it will oxidize and heat up your cat. The fuel does not just "sit" in your intake manifold because your engine still pumps air as it is spinning down to a stop. The spinning doesn't stop instantly, so if you kill just your spark the fueling continues as the engine spinning continues even though you don't feel the jerkiness of sputtering combustion.

You are correct that any fuel in the oil will light off as the oil temperature heats up. This also takes time at temperature and if someone is frequently EOCing and minimizing engine load rather than P&G the oil may not get very hot and may not stay hot long enough to light off frequent additions of fuel from a power-on shutdown. Bottom line: it's fine if you want to cut the ignition to shut off your engine, but for pete's sake cut the fueling as well!

[Raysp30]

Can't seem to find anything that would be the fuse I'm looking for. There is no fuel injector fuse or a PGMFI fuse. Anybody able to help locate on an 89 crx?

If not, anybody have other ideas for a good kill switch method? The only one I'm still able to find that I know I can do is the fuel pump, and I don't really want to cut that one.

[bbjsw10]

Originally Posted by Raysp30

Can't seem to find anything that would be the fuse I'm looking for. There is no fuel injector fuse or a PGMFI fuse. Anybody able to help locate on an 89 crx?

If not, anybody have other ideas for a good kill switch method? The only one I'm still able to find that I know I can do is the fuel pump, and I don't really want to cut that one.

Use the wires on 87a and 30 on your Injector resistor power feed. Will work the same way. I ended up changing mine to this after writing how-to. I believe the injector resistor on your car should be close to brake booster and look like this.

[Raysp30]

Originally Posted by bbjsw10

Use the wires on 87a and 30 on your Injector resistor power feed. Will work the same way. I ended up changing mine to this after writing how-to. I believe the injector resistor on your car should be close to brake booster and look like this.

I think I see what you mean. Just cut into the red wire (power feed) and plug those into the relay? Do I still need to use the inline fuse with this setup? Appreciate the help.

[bbjsw10]

Originally Posted by Raysp30

I think I see what you mean. Just cut into the red wire (power feed) and plug those into the relay? Do I still need to use the inline fuse with this setup? Appreciate the help.

I would atleast use some type of fuse. Better safe than sorry.

[Impulse]

You guys should use a spdt relay and a momentary switch to disable the ignition, fused off of the igntion at or near the ignition switch itself. Pin 86 to the momentary switch, then the switch to ground, cut the ignition wire open, pins 30 and 85 will go to the wire coming off your ignition tumbler itself, and pin 87a goes to the ignition wire going down towards the car. Doing it this way, the relay ign connections are already fused through the factory wiring, but you should put a fuse between the chassis ground the momentary switch. If the relay ever fails it will rest at normally closed, and you ignition will still be connected, plus there are not wires through the firewall. If you guys like I can give people tech support and wires colors for your vehicles because I have access to it since I am a 12 volt installer. Just shoot me a pm. Just my .02 cents.

[bbjsw10]

The way I have this drawn up on schematic it goes back to a normally closed position. I would not cut into wire by ignition switch shuts off more than you need to shut off. Like your ecm and odometer all in one shot, and the all important ABS system and airbags. This is why I would not cut ignition off at switch with relay. Plus need odometer to figure mileage. I have installed also since 1995 and was Install manager at local ABC warehouse for about a year.

Originally Posted by Impulse

Pin 86 to the momentary switch, then the switch to ground, cut the ignition wire open, pins 30 and 85 will go to the wire coming off your ignition tumbler itself, and pin 87 goes to the ignition wire going down towards the car.

FYI: the way you describe you have the relay connected on normal open contacts. 87a is normal closed.

[Raysp30]

I had a relay from Radioshack that had 4 pins on it, no 87a. I hooked it up by splicing into the red wire on my fuel injector resistor. Once all the wires were in place I tried starting the car and it wouldn't turn over.

I found a different relay that was supposed to have the 87a pin on it, but there was only a stub where the pin should have been, and the packaging on that relay had never been opened.

Is there a 2nd wire I need to splice into to make this work?

[Gregte]

Regarding the concerns of cutting the ignition and then having a few extra cycles of fuel injected, carbureted cars do it every time you turn off the key switch.

[bbjsw10]

Originally Posted by Raysp30

I had a relay from Radioshack that had 4 pins on it, no 87a. I hooked it up by splicing into the red wire on my fuel injector resistor. Once all the wires were in place I tried starting the car and it wouldn't turn over.

I found a different relay that was supposed to have the 87a pin on it, but there was only a stub where the pin should have been, and the packaging on that relay had never been opened.

Is there a 2nd wire I need to splice into to make this work?

Get a relay from autozone or advance auto and preferably a Bosch relay. It will have to have all 5 like listed on the parts needed list. That or find a 4 pin normally closed relay.