In the following paras, I am making an attempt to bring home some basics of what all make a Car tick and what can possibly go wrong. So let’s begin from the beginning…….

How does an Engine Start

For starters, it's just like a Bike which starts when you kick it - with its Ignition AND Fuel supply switched on !

As regards a Car with a 'multi-cylinder' 4-Stroke engine, not that a 2-stroke would make any difference, let's look at the following fundamentals :

1) We all know that an ICE has pistons inside its cylinders 'connected' to the 'Crank-shaft' by means of connecting rods. This way, the reciprocating motion of the pistons is converted into a rotary one of the Crankshaft - just like the exposed ones of a Railway Steam Loco. The image below should help get a clearer picture –

2) The top-end of a piston's stroke is known a 'top-dead-centre/TDC' and like wise the bottom/BDC.

3) A 4-Stroke/ICE has to have a minimum of 1-Inlet Valve and 1-Exhaust Valve. These valves are opened/closed at the designed 'timing' by the 'Camshaft', which is driven by the Crankshaft at 1/2 its rpm by means of either a 'timing-chain' or a 'toothed rubber belt' - as in most Cars today.

4) Stroke 'one' of a 4-S/ICE is called the 'suction stroke'. This happens when the piston moves downwards from its TDC with the inlet valve open. This allows it to 'suck-in' appropriate mixture of Air and Fuel - either via a Carburettor OR by 'injection' as in Mpfi Cars today. When the piston reaches the BDC, the inlet valve closes.

5) On its return stroke from such a BDC, the piston begins to 'compress' the A/F mixture it drew-in in the previous stroke AND during this stroke, both its Inlet and Exhaust valves are closed. This/'Stroke-2' is called the 'Compression stroke'.

6) Just before it reaches the TDC - a point calculated by design/experience - the Electrical Ignition System of the Car sends a high voltage pulse to its Spark Plug. The pulse is strong enough to enable it 'jump across' the SP's calculated/pre-set 'gap' inside the Cylinder under such conditions – usually at a pressure of 15 kg/cm.

7) Such a spark ignites the explosive A/F mixture within the cylinder, which is already compressed to around 15 times the Atmospheric pressure by now, and it goes off like a bomb inside the cylinder. Both the I/E valves are still closed.

8) Since such explosive gases are so 'contained' within the cylinder, the piston gets pushed back to its BDC with all their force. This/'Stroke-3' is called the 'Power Stroke'. After it reaches the BDC, its return stroke to TDC commences.

9) Just when the piston so hits its BDC, only the Exhaust valve is opened via the Camshaft and on it's such upward stroke - #4 - called the 'Exhaust stroke' - the burnt/expended gases are 'driven out' of the cylinder via the tail pipe by the time the piston reaches its TDC. At this point, the Camshaft closes the exhaust valve and soon thereafter - opens the Inlet Valve for the suction stroke to commence as per (4) above.

Hereafter, having been so 'cranked' either by a pedal kick or an Electrical Starter Motor - provided it's revved to atleast half its idling speed and A/F mixture + Electrical Spark is available as per its needs - the engine can continue to run by itself. In other words, it has 'started'.