Simple Fuel Pump Kill Switch! [BEWARE] Episode 1

How to install a basic kill switch (Fuel pump) in your car. What are the problems? What are the benefits? What can we do better? - Comment with your suggestions!
Car used: Abarth 595

[@falsedragon33]

My issue with a switch is the pump is an inductive motor. When the power is cut off, the pump motor will do what any inductor will do. Resist the change of current causing voltage to spike to a very high level. So you need a flyback diode on it, if it doesnt have one built in. To test, connect a oscope to the power then cut power to tye pump. Observe the voltage jump. Or turn the stereo on and see if it pops the speakers. The large voltage spike (EMP), couples onto the speaker wires, casuing the pop.

[@richardcrowell284]

It's not currents it is amperes (amps) the best way to wire a kill switch is pick it up under the dash, a fuel pump would draw a maximum of about four to six amps. Use a decent switch preferably a push pull switch as they are usually rated at twenty five amps and have a smaller mounting hole making it easier to fit under the dash. Use some 4 or 5 mm square automotive cable to make the connection. I prefer to solder the joins as this will prevent overheating the connection. I have fitted hundreds over my time as an auto electrician.

[@Henry.Riccato-Smith]

Thanks for the pointers Richard. Good to note about soldering the connections for better heat dissipation. What are your thoughts on wiring up a switch to the fuel pump VS the from the ignition?

[@tconners1758]

Hello, sorry to bother, for those of us that can’t solder, would you think a suitably rated wago block would be ok?

[@Henry.Riccato-Smith]

@@tconners1758 Richard can confirm but I would imagine so - using a wago would make it slightly more difficult to hide.

[@tconners1758]

@@Henry.Riccato-SmithI think I’m going to remove the rear door cards and access the wiring there as opposed to directly above the fuel pump, that way the wagos will be behind the door card and unable to be seen. Thankfully. Cheers for the response. 🙏🏻

[@falsedragon33]

Current is measured in amps. It's okay to use then interchangeably. If you had to use only one, you would use current, so you are consistent. You would never call an inductor a Henry, or a capacitor a Farad.