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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It will vary by car (diesel v gas, fuel injection v carburetor, etc…). For a modern 4-cycle gas engine:
1. Immobility sensor detects chip in key.
2. Turn to first click. Basic electric circuits energized (windows, radio, etc…)
3. Turn to second click. Engine sensors activate, fuel pump pressurizes line, engine systems are ready to run (which is why this is the position the key is in when you’re driving).
4. Turn to third click. Starter motor engages, cycling the engine.
* A fuel/air mixture is injected into each cylinder as the piston is drawn down by the rotating crankshaft.
* The piston rises in the cylinder, compressing the fuel/air mixture.
* The ignition system fires the spark plug, igniting the fuel/air mixture.
* The expanding ignited gasses force the piston back down. (This is what you feel when you accelerate – the forces of that contained explosion channeled through the crankshaft, transmission, and on to the wheels.)
* Once this process begins, you return the switch to the second position (see 3.)
There are many other things going on while the engine begins to spin and then runs. A belt or chain attached to cam shafts open and close the intake and exhaust valves (that fuel/air mixture – and the burned gasses – have to get in and out of the cylinder/combustion chamber). A water pump turns to cycle coolant through the engine. An oil pump turns to supply lubrication to the moving parts. You can get down to all sorts of levels of specificity.
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