Once I put my key in the ignition and turn the car on what are the sequence of events that take place?
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The key is just electrical switch. Trough relay it turns on starter, that starts the engine.
As the engine moves, it works like normal… Sucking air/gas mixture until it starts the 4stroke cycle…
From thet point your engine is on… And you stop your starter
The battery is turned on in the first key position and the accessory position allows the electrical system to power things like the radio and wipers. When the key is further turned to the start position the starter motor meshes a gear with the flywheel gear attached to the engine crankshaft. The starter motor then engages and uses its gear to turn the engine over which moves the pistons to start the four stroke cycle. These four strokes are intake, compression, combustion, and exhaust. As the engine turns, fuel and air enters the engine cylinders as the intake stroke. Then the piston moves upward to compress the fuel air mixture as the compression stroke. When it is fully compressed the spark plug fires to ignite the fuel air mixture and the hot expanding gasses force the piston back down as the combustion stroke. And finally the gasses are exhausted from the cylinder as the exhaust stroke. All of the cylinders will do these four strokes in sequence and the engine will now be self sustaining. Then you release the key and it springs back to the on position where the engine is running and charging the battery.
When you turn your key to the start position it completes a circuit with the starter. The starter moves a little gear into place to match up with a very big gear that is attached to the spinning parts of your engine. The starter will use electricity from the battery to spin the big gear, starting the process of your engine moving. Once the engine parts are moving, igniting gasoline can take over the process to keep the engine moving.
If you have accidentally turned the car over while it was already running that awful noise is from the starter trying to move the little gear into the big gear, but the big gear is already spinning.
Key goes in, car detects key and some minor electrical functions start.
Key rotates to first click, whole electrical system starts up.
Key rotates second click, ignition turns on and the car is electrically ready to go.
Key rotates past second click. Starter motor swings gear into contact, spins engine shaft. Engine is turned over, sucks in fuel and air, starts the combustion process.
Key is released back to second click. Starter gear disconnects and motor stops. Car is running normally.
The starter motor is engaged and it spins the crankshaft of the engine. Simultaneously, the ignition is set to ‘on’ which allows the ignition coils to be powered by the battery. As the crankshaft turns it articulates the pistons which start getting fed fuel / air mixture from an electronically controlled injector (most modern cars) or a carb. Once the cylinders fire they create enough power to maintain idle and the starter motor is turned off.
My confusion is push to start… why do you need to put your foot on the brake and what happens if you don’t?
Most of the other answers omit: the computer in the car talks to the chip in the key to make sure the key is the real and proper key, before allowing the engine to start.
Unless you have a US Kia, that is. Many of them don’t have that feature, making them much easier to steal.
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Brain Processes Car Ignition

When you turn the key in the ignition to start your car, several processes occur that enable you to perform this action. Let’s break down the sequence of events:
Intent and Motor Planning: Initially, your brain generates an intention to start the car. This intention activates a network of brain regions involved in motor planning, which includes areas such as the prefrontal cortex, supplementary motor area, and primary motor cortex. These regions coordinate the movements required to turn the key.
Sensory Processing: As you reach for the key and grasp it, sensory information is sent from your hand to the somatosensory cortex, the region responsible for processing tactile sensations. This allows you to feel the key’s shape, texture, and temperature, providing feedback to your brain.
Motor Execution: Once you have a firm grip on the key, your brain sends signals to the motor neurons that control the muscles involved in rotating your wrist, hand, and fingers. This signal originates from the motor cortex and travels through the spinal cord to reach the appropriate muscles in your hand.
Proprioception and Feedback: As you turn the key, your brain receives proprioceptive feedback from receptors embedded in your muscles, tendons, and joints. Proprioception provides information about the position, movement, and tension of your body parts, allowing your brain to monitor and adjust the force and direction of your movements.
Visual Processing: Simultaneously, your brain processes visual information from your eyes, enabling you to see the key and the ignition switch. Visual cues help you accurately guide the key towards the ignition and align it correctly.
Coordination and Control: Your brain continuously integrates sensory feedback and adjusts the motor commands to ensure precise control of your hand movements. It monitors the position and rotation of the key, making necessary corrections until the key fits into the ignition switch.
Activation of the Car’s Systems: Once the key is fully inserted and turned, electrical signals are transmitted from the ignition switch to the car’s electrical system. At this point, the brain’s involvement becomes minimal, and the car’s internal processes take over to initiate the starting sequence, including fuel injection, spark ignition, and engine cranking.
It’s important to note that the above explanation simplifies the complex neural processes involved in starting a car. Multiple brain regions work in harmony to coordinate the fine motor control, sensory integration, and cognitive processes required to accomplish this task smoothly.
Assuming a basic car:
There’s a little contactor that closes that energizes all the switched 12 V circuits: things like the radio, the AC system, engine ignition, and the fuel pump.
That’s about it. That answers your question.
If you want more information related to your question, but not specifically asked:
If your turn to ACC instead of ON, then the the engine and fuel pump does not get power, but the other accessories do.
If your turn the key to Start. another contactor closes to spin the starter motor, and start the engine.
Most people don’t turn a car to ON unless then also want to start it. That’s what ACC is for.
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