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Ignition Cut Off Switch?

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Quarterwave

Ignition Cut Off Switch?

Hi everyone,

I'm just about to pull apart the interior on my truck to install some sound deadener and new carpets.

While I'm at it, I'd like to run some wires for a powered sub and an ignition kill switch - I'd like to hide the killswitch in the truck somewhere to be determined.

With that in mind, what is the general consensus on wiring in the killswitch?

- By running wires from the switch to the battery? (If so, what gauge?)
- By tapping in to the steering column ignition wires? (If so, what colors and what gauge wire from the tap to the switch?)
- By tapping into the fuse box? (If so, with a spade connector? Or to make it look factory, how can I hard-wire it into the panel, as there are a lot of empty slots in the panel?)

Any help is appreciated in advance, as I'm trying to plan this all out before I gut the cab.

Thanks!

1985 Ford F150, 2WD.
351 H.O Windsor, aluminum heads
Cam: Lift = .496''/.520'' Duration @ .050: 224°/234°
C6 Transmission
6" Rough Country Lift
33x12.5x15 BF Goodrich All-Terrains
15x10" Pro Comp Rims

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

Don't put a switch in the battery circuit. Instead, kill the ignition. On trucks with full gauges there's a dark green/yellow wire running from the ignition module & coil to the tach - even if you don't have a tach - as shown on Page 18 & 19 of the 1981 EVTM. All you have to do is to ground it and the ignition is dead. The engine will spin like it is going to start, but without spark it won't run. And no amount of jumping is going to make it run until that ground is removed.

As for a switch, do you have dual tanks? If so, do both work? If you have dual tanks and one doesn't work then use the tank switch to ground the ignition. No extra switches.

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

Quarterwave

Re: Ignition Cut Off Switch?

Thanks Gary.

I do not have a factory tach, but I did install a 5" Autometer tach and wired that in myself with new wiring.

I also do have dual tanks but have not tried switching them yet - lot's of other things to sort out and the rear tank is at the end of that list, but thanks for the tip - I would never have thought of that.

After looking at the link in your message, I do not understand what "EEC" is - my 351W is a carburetor-fed engine. I would think that "EEC" stands for "Electronic Engine Control" - and if that is correct, how would that apply to a non-fuel injected engine?

Also, what are my options if I want to keep the rear tank for later use?

I am not making the connection between grounding the factory-installed tach wire and it killing the ignition. What do I ground it to - one side of the after market switch? If so, is there a hot lead that I also need to consider?

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

EEC is Electronic Engine Control. But that's on Page 20 and following. I pointed you to pages 18 & 19, Duraspark, as that's what you have with your 351W HO.

As for how the ignition works, the red/light green wire supplies power to the coil, and the ignition box, shown as "Ignition Module" and "Solid State" in the diagram, alternately grounds the dark green/yellow wire and then takes the ground off as directed by the pickup module in the distributor. During the time the dg/y wire is grounded, meaning taken to ground or 0 volts, current flows in the coil and the coil is "charged". When the ground is removed the charge dissipates by causing a large high voltage surge to flow out the black wire, through the distributor, and to a spark plug.

But if you ground the dark green/yellow wire then nothing the ignition module does will cause a spark, and the engine cannot run. And, by "grounding it" I mean take it to a simple toggle switch and take the other side of that switch to ground. When you close the switch the engine will not run.

As for your rear tank, if you want to use it at a later date then don't wire into it for this. Instead, put a small toggle switch under the dash where it isn't easily seen but is easily reached. Orient it such that with the handle forward the truck will run, and with the handle back the truck won't run.

Gary, AKA "Gary fellow": Profile

1986F150Six

Re: Ignition Cut Off Switch?

Administrator

Someone in the past, wired the kill switch such that when the cigar lighter [which they did not need] was pressed in, the coil was grounded. By pulling out the cigar lighter, the engine would start.

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

I like the cigar lighter idea. But you wouldn’t be able to use it to charge a cell phone while driving. Hmmmm! 😜

Gary, AKA "Gary fellow": Profile

Quarterwave

Re: Ignition Cut Off Switch?

In reply to this post by Gary Lewis

Thanks Gary.

It has a small LED light in the toggle switch, which (when power is running to it), turns on when the switch is in the "on" position.

Quick questions:

1) Can I safely run 14ga wire or does it need to be something beefier like 8 ga?

2) Ideally, I wanted to hide/mount the switch near the location where I will mount the powered sub (under the rear seat in the supercab, or to the seat frame of the rear seat), as that way it won't be anywhere near the dash and really out of the way. Can you foresee that presenting any electrical issues?

3) To clarify - tap into the dark green/yellow wire and run the tap to one side of the switch. Then, ground the switch to the chassis of the vehicle, correct?

4) For the ground, can it be a bolt from the seat frame or maybe tap into the ground for the powered sub? Or is that asking for trouble?

Thanks!

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

The LED might actually glow when the engine is running as there will be voltage on that wire. In fact, if I remember correctly I saw in excess of 35v when I put my scope on it, so it might blow the LED.

As for the wire size, #20 would probably work. The wire to the tach, the dark green/yellow is probably a #16, so that's what I'd use but it isn't critical. And, you are tapping into that wire. But, if it was me I'd prove the theory by taking a jumper wire and shorting the dark green/yellow wire to ground and trying to start the truck. You can easily get to that wire on the coil - the terminal marked "Tach".

You can place the switch anywhere that is convenient. However, there will be some electrical "noise" in that wire so I wouldn't bundle it tightly to the input of the subwoofer as you might be able to hear the noise in the sub.

As for the ground, and ground will do and the seat bolt should work fine. Or the one for the sub will be fine.

Gary, AKA "Gary fellow": Profile

Dyn Blin

Re: Ignition Cut Off Switch?

Some additional advice :

Make sure you have the correct DG/Y combination.

There are two sets of dark green / yellow wires going into the cluster. One has DG/Y the long way. The other is a DG/Y with the yellow "dashed".

The tach is the dashed yellow on dark green.

Ground the other/wrong one and you'll have all the magic smoke escape after the insulation burns.

DAMHIK.

Sonoma County,CA
1982 F150 Flareside XLS
NP435 4x4
351W Motorcraft 2150

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

Oops! Sorry!

Did you get the magic smoke back in?

Gary, AKA "Gary fellow": Profile

Dyn Blin

Re: Ignition Cut Off Switch?

Heh.

All is well here.

I have the dash off for other reasons and since I had my EVTM close by, I double checked before I tapped.

I haven't always been so careful in the past. Once (wires) burned, twice shy.

Figured I would pass it on while it was on my mind.

Sonoma County,CA
1982 F150 Flareside XLS
NP435 4x4
351W Motorcraft 2150

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

Good. So, did grounding it kill the ignition?

Gary, AKA "Gary fellow": Profile

Dyn Blin

Re: Ignition Cut Off Switch?

This post was updated on .

Oh yes. It just spins, & sounds like it's about to catch, but never does.

I used 18 guage wire & it doesn't get hot. Ring terminal (grounded) to the switch and a blue Positap for the tach wire.

It'll be good for the lazy thieves. The smart ones will disconnect the shaft and tow it. I don't know many young bucks that even know how to drive a clutch, unless they are off the farm.

Sonoma County,CA
1982 F150 Flareside XLS
NP435 4x4
351W Motorcraft 2150

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

I thought that would be pretty effective.

Gary, AKA "Gary fellow": Profile

Dyn Blin

Re: Ignition Cut Off Switch?

Indeed. Kudos to you! Simple & effective.

Sonoma County,CA
1982 F150 Flareside XLS
NP435 4x4
351W Motorcraft 2150

Quarterwave

Re: Ignition Cut Off Switch?

In reply to this post by Gary Lewis

Hi Gary,

I'm going back to this thread as most of my interior is now in the truck and I'm at the point of adding in the kill switch.

As I was re-reading this thread, there was a mention of grounding the cut off switch and it didn't make sense to me - in that the switch that I have is a simple, on-off type of switch that has two connections on the rear of it. Here is a link to the exact switch:

https://www.amazon.com/gp/product/B00ZWWZ0GK/ref=oh_aui_detailpage_o02_s01?ie=UTF8&psc=1

Currently, I have this mounted and hidden with two wires coming off it - ready to be added into the ignition circuit... should one of those wires be grounded?

By my understanding (and please, correct me if I'm wrong), I need to find the green/yellow wire (is that in the column?) cut it, connect one side of the cut wire to the wire that is connected to the "off" terminal on the cutoff, and then connect the other side of the cut wire to the wire that is connected to the "on" terminal of the cut off.

Is that correct?

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

Yes and no, in that order.

Yes, you have a switch that will work. But no, don't hook it up that way.

You want the dark green/yellow wire that is coming from the coil, as shown here, and is going to the tach, as shown here. I don't think it will be on the steering column, but it will be going to the instruments, and you could get to it fairly easily by pulling the instrument cluster out and disconnecting it from the harness. That would give you pretty good access to the wire.

But you want to tap into that wire, leaving the wire intact, and take the wire that you've connected to the dark green/yellow wire to one side of your switch - and it doesn't matter which side. Then, take a wire from the other side of the switch to ground. Presto, when the switch is On the engine cannot run.

Why you might ask? Because the coil is grounded and nothing the ignition module does can create a spark.

Gary, AKA "Gary fellow": Profile

Quarterwave

Re: Ignition Cut Off Switch?

Thank you for the education, Gary.

I have no tach in the cluster but from what I've read in the threads here, the wiring should be all there, so I'll pull the cluster out this weekend.

Much appreciated!

Gary Lewis

Re: Ignition Cut Off Switch?

Administrator

Welcome. If you can install the switch so that it is open when the lever is pushed forward and closed when it is pulled back then you could think "forward to go, backward to stop" - or somesuch.

Gary, AKA "Gary fellow": Profile

Quarterwave

Re: Ignition Cut Off Switch?

Yeah, at the moment, I have it as "up" is on and "down" is off.