Fuel cutoff switch - Whats the best/easiest way?

bloopbloob · Mar 27, 2008

Well i think its about time i did something to make it harder to steal the stang.... whats the best way to disable these cars from being started and driven without a key? Fuel cutoff switch? any info towards what to do would be appreciated. thanks

BK_CAULEY · Mar 27, 2008

if your car has the relay under the seat just splice a switch into one of the wires to cut power. if the relay is under the hood run longer wires.

Fett · Mar 27, 2008

Personally, I wouldn't use the fuel pump as a theft device. Granted it is a VERY slim chance, but what if a connection you make becomes loose or the switch you use fails when driving?

In my opinion, the best way to make a kill switch is by splicing into the constant 12v to ignition switch and putting a flip switch inline. I have mine hooked up like that with a switch that must be triggered in order to start the car.

BK_CAULEY · Mar 27, 2008

splice it into the 12v on the coil same concept i guess

bloopbloob · Mar 27, 2008

ok thanks. so what kind of wire (like what Ga) and switch will i need to do either of these ideas safely?

BK_CAULEY · Mar 27, 2008

12 guage wire and any decent size toggle switch should do

Fett · Mar 27, 2008

BK_CAULEY said:
splice it into the 12v on the coil same concept i guess

Wouldn't a failure in that splice also stop power to the coil while driving?

I'm sure it would be safe, but I am just leery of screwing around with anything that is vital to vehicle operation while the motor is running.

Nova · Mar 28, 2008

i plan on splicing into the control side of fuel pump relay under the drivers side seat. im not sure where im gonna put the switch yet. but i want it to be out of the normal checking places.

Informant736 · Mar 28, 2008

Not trying to Hijack this thread but, I'm about to do a battery relocation and am using the moroso disconnect switch. Would this be an option for you to disconnect the battery so it wouldn't start up, not sure where you would mount this if you haven't relocated your battery. Just putting out an option.

ChopSuey · Mar 28, 2008

On my old LX i used a GT headlight/foglight switch and wired the fuel pump relay to the foglight switch. To start the car the foglights had to be on. Factory look so who is going to think about it.

Informant736 · Mar 28, 2008

I like the above post, always thought about doing that for a nitrous toggle but it could deffinatly work with a fuel cut-off

LiquidGT · Mar 28, 2008

I have a kill switch on my fuel pump, I put the switch on the trigger side of the relay and not on the fuel pump power side, I cant remember the wire color right now. When its activated the car will still start, but it will run like chit then it will run out of gas quick so the theives wont get far.

Now that I think about it I should've spliced into the clutch safety switch, but I didnt have a clutch back then so I didnt think about it.

bloopbloob · Mar 29, 2008

LiquidGT said:
Now that I think about it I should've spliced into the clutch safety switch, but I didnt have a clutch back then so I didnt think about it.

can you please explain this more? that sounds like a better idea than cutting fuel...
but i really don't know for sure what you're talking about? is that what makes the car not start if the clutch isn't depressed? how hard is it to do this?

Rick 91GT · Mar 29, 2008

The clutch switch is very easy to disable, I wouldn't use that for a anti theft device. The fuel relay which BK mentioned is the best option.

The battery cut off is easily identified, not a good anti theft.

jrichker · Mar 29, 2008

Follow this tech note for the best way to wire a fuel pump kill or anti-theft switch...

On 86- 91 cars the fuel pump relay is under the driver’s seat, 92 and later cars, the fuel pump relay is under the Mass air duct on the passenger fender well.

Note that the wire colors changed in 1991, so there are two different descriptions.

86-90 model cars:
Cut the red/black wire going to the fuel pump relay. Splice a 16 or 18 gauge wire into the wire and connect it to one side of the switch. Connect the other side of the switch to the other end of the red/black wire going to the fuel pump relay. When you are done the switch should be in the middle of the spliced red/black wire that goes to and comes from the fuel pump relay. Using the control side of the circuit allows you to use light gauge wire and light duty switches. There is less than 1 amp going through the circuit, so you don’t have to worry about voltage drop across the wiring depriving the fuel pump of electrical power.
See http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model wiring diagrams.

91-93 model cars:
Cut the Lt Blue/Orange wire going to the fuel pump relay. Splice a 16 or 18 gauge wire into the wire and connect it to one side of the switch. Connect the other side of the switch to the other end of the Lt Blue/Orange wire going to the fuel pump relay. When you are done the switch should be in the middle of the spliced Lt Blue/Orange wire that goes to and comes from the fuel pump relay. Using the control side of the circuit allows you to use light gauge wire and light duty switches. There is less than 1 amp going through the circuit, so you don’t have to worry about voltage drop across the wiring depriving the fuel pump of electrical power.
See http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model wiring diagrams.

LiquidGT · Mar 29, 2008

bloopbloob said:
can you please explain this more? that sounds like a better idea than cutting fuel...
but i really don't know for sure what you're talking about? is that what makes the car not start if the clutch isn't depressed? how hard is it to do this?

I never put any deep research into it, it just came across my mind when I saw the jumper wire when I did my pedal swap. I guess it would be possible to put a switch in between the clutch wires, therefore making two clutch safety switches. So the car wont start even when you press the clutch, but dont quote me on that I havent looked at any wiring diagrams or tried it on my own car.

Rick 91GT said:
The clutch switch is very easy to disable, I wouldn't use that for a anti theft device.

I dont know much about how to steal cars, but how would the clutch switch be any easier than disabling a fuel pump switch? I think it would be harder since its way up in the dash.

If the clutch switch theory is true then do both, it would make it just that much harder to steal the car.

S&B · Mar 29, 2008

its nice having a switch so when your relay overheats from running too big of a pump you can shut it off before your car burns down as well

Fuel cutoff switch - Whats the best/easiest way?

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