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.