Eli5: Why does pressing the accelerator helps when the car engine is not turning on?
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Depending on the vehicle, there may not be enough fuel. Pressing the gas is much like priming and engine that won’t start. You force a bit more fuel into the motor in hopes a spark will cause ignition.
If the motor is getting more fuel and some of the cylinders are firing but it won’t turn over, the extra fuel in the cylinder helps warm the vehicle up further. Atomizing fuel and causing an easier reaction.
Anymore, as soon as you turn the ignition to accessory…on but not started, the car will prime the motor with the correct amount of fuel. Some prime the motor when you unlock the car.
For the most part, fuel injection and computer software of vehicles nowadays prevent you from adding too much fuel. Typically it’s a bad spark plug, fuel filter, or plug(connects to spark plug and ups the voltage to get a good spark).
In short, it dumps more fuel in hopes of an easier ignition, too much fuel will flood the motor and a spark will not be made.
This is especially true of older cars with a carburetor.
A car engine requires a specific mixture of fuel and air to start and run efficiently.
When a car engine is warm, the air that it pulls in to mix with the fuel tends to also be warm. Warm air is less dense than cold air. This means that when the engine is warm it needs less fuel mixed with the air than when the engine is cold. This air fuel mixture is what is detonated inside the engine eventually to make power.
Stepping on the gas pedal on one of these older cars connects to a mechanical linkage in the carburetor that squirts more fuel into the engine which can help with that air fuel ratio when the engine is cold.
You have to be careful though, because you can squirt too much fuel into the engine, which is sometimes called “flooding it”
Stepping on the gas pedal while starting the car probably doesn’t make a difference in a fuel injected car (one made after the 80s.) Fuel injected cars have a computer that controls the air fuel ratio during start up. The computer is paying attention to things like air pressure, air temperature, and engine temperature and automatically squirts the appropriate amount of fuel into the engine.
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