what causes a vehicle not to start except when you pour gas in the carburetor?

If a vehicle only starts when gas is poured into the carburetor, it typically indicates a problem with the fuel delivery system. This could be due to a clogged fuel filter, a malfunctioning fuel pump, or a blocked fuel line preventing gasoline from reaching the carburetor. Additionally, issues with the carburetor itself, such as a stuck float or dirty jets, may also prevent it from properly drawing fuel. Overall, it suggests that the engine is not receiving the necessary fuel for normal operation.