What is a common cause for gasoline engines cranking but not starting?

A gasoline engine cranking but not starting often indicates that fuel is being introduced into the combustion chamber, but it may be present in excessive amounts, leading to what is commonly referred to as an "engine flooded" condition. In this situation, there is too much fuel relative to the air, which can prevent the engine from igniting and starting properly.

When an engine is flooded, the spark plugs can become saturated with fuel, inhibiting their ability to produce a spark needed for combustion. In this scenario, even though the engine cranks—meaning the starter motor is functioning and the engine's mechanical components are moving—the presence of excessive fuel creates a barrier to starting.

Understanding engine flooding is crucial because it can often be remedied by allowing the engine to sit briefly to let the excess fuel evaporate or by using a starting technique that minimizes fuel intake, such as holding the throttle open while cranking to introduce more air into the mix.