* To increase the air-fuel mixture. When the engine is cold, it needs a richer air-fuel mixture to start than it does when it is warm. The extra fuel is needed to help vaporize the gasoline and make it easier to ignite. Pumping the gas pedal increases the amount of fuel that is injected into the engine, which helps to create a richer mixture.
* To increase the RPMs. When the engine is cold, the oil is thicker and the battery is weaker. This can make it harder for the engine to turn over at the normal starting speed. Pumping the gas pedal increases the RPMs, which helps the engine to overcome the increased resistance and start.
* To clear the spark plugs. When the engine is cold, the spark plugs can become fouled with debris. This can prevent the spark from jumping across the gap, which will prevent the engine from starting. Pumping the gas pedal helps to clear the spark plugs and make it easier for them to ignite the fuel.
