Turn the key or press your car’s starter button, and magic happens as the engine roars to life. (Okay, so we’ve all had those mornings when it doesn’t, but work with me here.) You know how to make the vehicle start, but do you know exactly how it does it?

It’s actually a pretty complicated process that depends on a number of components and sensors, all of which have to work together to make it happen.

First, it’s important to know how an engine works. Pistons move up and down to turn a heavy central crankshaft whose spinning motion eventually turns the wheels, similar to the way your legs power a bicycle. The pistons are powered by the explosive force of gasoline vapour. The fuel-air mixture comes in, and combusted exhaust gases go out, through valves that are opened and closed by the camshaft.

When the engine starts, the crankshaft is the first of those internal components to move. As it starts to spin, it moves the pistons in their cylinders. It also turns the camshaft, which is connected to the crank via the timing belt and spins in conjunction with it. That gets the valves moving, which lets in the fuel. The engine now runs on its own, but something had to initially start the crankshaft moving.

On the earliest cars, it was human power. Drivers had to insert a handle into the front of the engine to engage the crankshaft, and then manually turn it. Cranking the engine this way could be difficult and even dangerous. The handle could spin when the engine started, potentially breaking arms or jaws.

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Before you get all nostalgic, trust us when we say the look of mock-shock would’ve quite likely turned to actual horror once the engine caught

Cadillac’s introduction of the electric self-starter for 1912 changed automobiles forever. It also marked the beginning of the end for steam-powered and electric cars, which were inferior to gasoline vehicles in their range and complexity, but which didn’t need to be cranked.

The original electric starter just mechanized what drivers had to do by hand, and today’s cars still use that same basic principle. Attached to the crankshaft’s flywheel is a large, round, and toothed ring gear. When you turn the key or press the button, a small gear on the starter motor moves and meshes with the ring gear. The starter motor then spins this small gear. That gear spins the ring gear, and the crankshaft starts to turn.

Before all this happens, though, the car has to confirm that it can set the process in motion. The ignition “talks” to the key or remote fob to ensure it’s a match to the car. Transport Canada requires all new vehicles to use electronic chips, even those with key-operated ignitions, to help prevent theft. Once that’s confirmed, the powertrain control module (PCM) signals the relays that govern the starter, fuel pump, and ignition to start their sequences.

Once the starter turns the crankshaft, the system now has to supply fuel to the cylinders, as well as electrical impulses to the spark plugs to fire and ignite the fuel. If fuel or spark don’t arrive at the right moment, the engine will crank but won’t fire, resulting in that disheartening sound that’s saying, “You’re walkin’, bud!”

So if it doesn’t all happen smoothly, what’s wrong? It could be any number of things, which is why troubleshooting a “no-start” condition on a modern car can be a time-consuming and frustrating operation.

Some possibilities:

– The key fob isn’t communicating with the vehicle. The fob battery could be dead, or there’s a malfunction in the vehicle’s keyless receiver module.

– Low or dead car battery. The battery powers the starter motor, which must turn the crankshaft fast enough to initiate the start sequence. Most people replace their batteries only after they’ve failed, instead of when they’re on their way downhill. Have your battery load-tested regularly, especially as it gets older.

– Poor battery connection. Excessive corrosion on the battery posts and cable ends can act like insulation between the two, preventing the electricity transfer from the battery to the starter.

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A modern car starter motor

– Starter failure. They only fire up for a few seconds each time you start, but they put their heart and soul into it. The enormous amount of power they draw and transfer means they can wear out sooner than many other vehicle components.

– Fuel flooding. Gasoline only burns when it’s mixed with air to form a vapour, and if too much liquid fuel gets into the cylinder, it can prevent combustion. All modern vehicles are fuel-injected, and they meter in the correct amount of fuel as the engine starts and idles. Keep your foot completely off the throttle until you actually start driving, to prevent flooding the engine.

– Bad spark plugs. If the spark plugs don’t fire and combust the fuel at precisely the right moment, the engine will run poorly and may not start at all. Replace or perform maintenance on any worn, dirty, or improperly-gapped plugs.