Fuel tank

From Futurepedia, the Back to the Future Wiki

"Damn, I ripped the fuel line."

—Marty

The fuel tank of the DeLorean time machine was a standard unleaded gasoline tank that was manufactured with the DeLorean DMC-12. Since the vehicle had an internal combustion engine that ran on ordinary gasoline, it was necessary to keep the tank intact as any total loss of fuel would leave the time traveler stranded. It is not to be confused with the fuel chamber which produced energy for temporal displacement.

When Marty McFly entered 1885, his encounter with the Pohatchee ripped open the car's fuel line and the tank went empty. Furthermore, Marty could not patch it in time since he had pulled into a bear cave which was still inhabited at the time.