Ignition Cut Off Switch?

[Quarterwave]

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!

[Gary Lewis]

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.

[Quarterwave]

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.

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]

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?

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.

[1986F150Six]

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.

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]

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.

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

[Quarterwave]

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.

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]

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!

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.

 

[Dyn Blin]

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.

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.

[Gary Lewis]

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.

Oops! Sorry!

Did you get the magic smoke back in?