Engine fuel system consists of fuel tank, fuel lines, fuel pump, fuel filter,
carburetor or fuel injection unit, air cleaner, air filter, and intake manifold.
Fuel is drawn from the tank through the fuel lines by the fuel pump, and
is forced through the fuel filter and to the carburetor or fuel injection
unit. At the same time, air is sucked through the air filter by engine
vacuum. The air and fuel are mixed together in the intake manifold
and then distributed to the cylinders. The ideal air-fuel ratio is
14.7:1 by weight.