The top three reasons a car leaks gas are a damaged fuel line, broken O-rings or injector seals, and fuel tank ruptures. Fuel system leaks are the number one cause of vehicle fires, according to the experts at How Stuff Works.
Fuel injectors seldom leak, but their rubber components are susceptible to corrosion and breakage. Fuel tank leaks are easily detected as gasoline spots on the pavement and appear as a rusty, corroded, weeping tear or puncture hole in a gas tank. Rubber fuel lines are a common leak source, as they are highly susceptible to the corrosive effects of gasoline, weather and road debris.