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human
[Back to the Future III] Why not combine parts from both DeLoreans?

The DeLorean Doc Brown possesses in 1885 has blown time circuits, while the one Marty arrives in has functioning time circuits but a ruptured gas tank and no fuel. So why not either take the time circuits from Marty’s DeLorean and install them in Doc’s DeLorean and go home? Or put the intact fuel tank w/ fuel from Doc’s DeLorean on Marty’s, and go home that way?
gpt
The one in the train tunnel has had it's fuel lines drained ready for long term storage - you can't leave half a tank of petrol in a car for 100 years it would turn to jelly and clog the engine.

The problem was not having any fuel, they could patch the fuel tank but not get any new fuel. Then they blew up something important in the engine (carburetor, maybe more) trying to run it on alcohol. They should have used coalgas, that might have worked.