When you first start driving, your engine might make that unmistakable clicking sound when you turn it off. It’s a sound that doesn’t seem to come from anywhere, and it’s not actually making any noise at all: the car is just turning off its fuel pump and relay. The relay is in your car between the engine and the body.
You can feel it click because there are wires going through it, but it doesn’t actually do anything except turn on the fuel pump and relay when you first start up… except for one thing: sometimes, if something isn’t plugged in properly or if something has been unplugged for some time, that relay might burn out. When this happens, your fuel pump won’t work anymore. If this happens to you, the best solution is to get a new relay instead of replacing the entire fuel pump.
These things can make a clicking sound in your car
It’s a fuel pump
Let’s tackle the question first: why does your car click when you turn it off? It’s because of a part called a fuel pump relay. A fuel pump is what helps move gasoline from the tank to the engine, and it needs electricity to operate. A fuel pump relay is what gives power to the fuel pump in order for it to work properly—when you start the car, this part switches itself on; when you shut off your motor, it switches itself off.
So that clicking noise after you’ve turned off your engine? That’s just the sound of a switch turning itself back into its original state. This process of resetting takes longer than switching on, but don’t worry: there’s no danger here! If your vehicle is making other noises besides this one or if its electrical system seems faulty in any way, though, be sure to bring it in for a checkup.
It’s a relay
You’ve probably heard the click of a relay before, even if you didn’t know what it was. In fact, your car has hundreds of relays that it uses in order to operate properly.
Relays are electromagnetic switches that allow a low-current circuit to control a high-current circuit (like turning on your car). The clicks you hear when starting your car come from slight vibrations that occur as the contacts open and close.
It’s an EGR valve
If you own a vehicle that tends to make click-click sounds after you shut it down, it is likely related to your engine’s EGR valve.
EGR stands for Exhaust Gas Recirculation. The purpose of your vehicle’s EGR valve is to recirculate a specific amount of your engine’s exhaust gas back through the combustion process. In doing so, this recirculated gas lowers the amount of NOx (a harmful pollutant created from the burning process) that is released into our atmosphere through your vehicle’s exhaust system. This helps us keep our air clean and breathable!
The clicking sound you hear after turning off your car or truck is simply the opening and closing of this valve.
It’s a solenoid
Solenoids are commonly used in control circuits for relays, electric motors and heating elements. They are used to “control a large amount of power with only a small amount of power”. A relay is like a light switch that runs on electricity instead of your hand. When voltage is applied to the solenoid inside the relay, the actuator is pulled up, switching on the device connected to it (like an engine starter).
For example, when you turn your ignition key, a small current flows through a wire winding around an iron core and generates an electromagnetic field—this closes a set of contacts to let the battery supply current to the starter motor. When you release the key, another set of contacts breaks the circuit. The coil’s magnetic field collapses and creates an electric spark — this makes a clicking sound as collapsing magnetic fields often do.