The Hill and the Carburetor

RAY: Here's the answer:

The car could climb short steep hills, but not long steep hills. A carbureted car has the ability to store gas for future use. The float chamber was being used up and by the time the car got to the top of a short hill, there was still gas in the reserve. But a long steep hill used up all the gas. The fix was a new fuel filter.

[ Car Talk Puzzler ]