Ever done a fuel pump kill switch?
- Thread starter 4turboho
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93 LX
Founding Member
well just use a switch to kill the fuel pump relay under your drivers seat.... It may be better just to kill the ignition at the switch as many alarms do...
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.
91-93 model cars:
Cut the Red 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 wire going to the fuel pump relay. When you are done the switch should be in the middle of the spliced Red 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.
diagram of the wiring for 91-93 cars.
AutoZone wiring diagrams
For 79-88 model Mustangs
AutoZone.com | Vehicle Selection - Year
For 89-93 model Mustangs
AutoZone.com | Vehicle Selection - Year
For 94-98 model Mustangs
AutoZone.com]AutoZone.com | Vehicle Selection - Year
For 1999-2005 model Mustangs
AutoZone.com | Vehicle Selection - Year
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.
91-93 model cars:
Cut the Red 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 wire going to the fuel pump relay. When you are done the switch should be in the middle of the spliced Red 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.
diagram of the wiring for 91-93 cars.
AutoZone wiring diagrams
For 79-88 model Mustangs
AutoZone.com | Vehicle Selection - Year
For 89-93 model Mustangs
AutoZone.com | Vehicle Selection - Year
For 94-98 model Mustangs
AutoZone.com]AutoZone.com | Vehicle Selection - Year
For 1999-2005 model Mustangs
AutoZone.com | Vehicle Selection - Year
Hey guys I have used this example and started to install a kill switch to the fuel pump relay. I have the wires run and switch setup I just wanted to confirm the wire colors before I put it in-line. The relay has these colors, Red, Green w/ Orange stripe, Green w/ Yellow stripe, and Yellow w/ green strip. I will be putting the kill switch in line with the red wire correct? I have a 93 and I thought my wire colors were different than what i have seen listed. Thanks
93 LX
Founding Member
why dont you just kill power to the coil? On my 90 its a white with pink wire coming off the ignition switch
You always say that 93 LX, lol.
But lets just say I have already set up to do the Fuel pump relay. What I need is to make sure is that I'm using the right wire to put the switch in. I'm thinking the red one but my wire colors seem different than the diagrams I have seen.
The Shape
Founding Member
This makes me think about back when I was a police officer. Before they started letting us take our cars home we had to leave them parked at the station after shift. In order to keep other officers from using/abusing my squad car while getting my gear out of the trunk I would always whack the inertia switch with my maglight. Many times I would have e-mails the next day from some officer that tried to use my car telling me it was broken down 
I know this doesn't help the OP, but that was my theft deterent system.
I know this doesn't help the OP, but that was my theft deterent system.
This got me to thinkin' about something. I don't think I have an inertia switch on my '84. I have the fuel pump relay under the driver's seat (it's a CFI car), but I've never seen a switch back there in the hatch area on the driver's side where it normally would be... 
LiquidGT
Member
I just spliced into the relay under the seat, I spliced into the trigger side of the relay and not the power side so the switch doesnt burn up. With the switch activated the car will idle like crap and die.
LiquidGT
Member
Yeah, it's the red wire.
The pink/blk and orange/blue wires are for power to the pump... don't want to use those.
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
The pink/blk and orange/blue wires are for power to the pump... don't want to use those.
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
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