A gas spill during fueling, a loose gasoline tank cap, a rupture in the gasoline tank or line or a leak in an engine combustion chamber can cause a car to smell like gas. Gasoline vapors are highly flammable and poisonous, and immediate attention is required to contain a leak.
Gasoline can be spilled during fueling due to improper alignment between the fuel nozzle and the gasoline tank receptacle. Holding down the fuel nozzle trigger before making contact with the tank receptacle or "topping off" the tank with excess gasoline can also cause spills.
Gasoline tank caps keep vapors contained within the gasoline tank and keep fuel from spilling out during vehicle movement. A loose or missing gasoline tank cap can cause gasoline fumes to escape from the tank, resulting in a gasoline smell.
A rupture in the gasoline tank or line can be located by searching for the source of dripping, pooling gasoline under the vehicle, or isolating the source of the smell to a general area of the vehicle. If the smell emanates from the rear of the vehicle, this could indicate that there is a rupture in the gas tank. If the smell emanates from the front of the vehicle, this could indicate that there is a rupture in the gas line, there is a leak in the combustion chamber, or the ignition timing is out of sync.