The smell of gas when starting a car is commonly caused by a few key issues. The simplest and most frequent reason is a loose or damaged gas cap that allows fuel vapors to escape. Another serious but common cause could be a fuel leak in the fuel lines, fuel injectors, or fuel tank, which is a safety hazard. Faulty fuel injectors or a malfunctioning fuel pressure regulator can also cause excess fuel to leak or not burn properly, creating a gasoline smell. Additionally, problems with the engine not burning fuel efficiently, such as worn spark plugs or issues with the oxygen sensor, can result in unburned fuel causing the smell. Problems with the evaporative emissions (EVAP) system or a damaged charcoal canister can also lead to gasoline fumes in the car. It is important not to ignore a gas smell as it can indicate dangerous leaks or engine issues, and it’s recommended to have the vehicle inspected by a mechanic immediately to ensure safety and proper repairs. Checking the gas cap for tightness and damage is a good first step before considering other causes.