Fuel System

DESCRIPTION

The fuel system mixes the fuel (gasoline) from the
fuel tank with air, and delivers the mixture, in the
form of droplets of fuel suspended in air, to the
engine.
The most important component of this system is
the carburetor, but besides this, the following
components are also important:
• Fuel tank
• Fuel line
• Charcoal canister
   (some models only)
• Fuel filter
• Fuel pump

The EFI (Electronic Fuel Injection) system is another
means of supplying gasoline to the engine

FUEL TANK

The fuel tank is constructed of thin sheet steel. It

is usually located in the rear of the vehicle to prevent
the leakage of gasoline in case of a collision.
The inside of the tank is plated to avoid rusting.
The tank is equipped with separators to avoid
changes in the fuel level when the vehicle is moving.
The mouth of the fuel inlet tube is located 2 to 3
cm above the bottom of the tank to prevent sediment
and water in the gasoline from being
sucked into the tube.

FUEL LINES

There are three fuel lines: the main fuel line, which
carries fuel from the fuel tank to the fuel pump;
the fuel return line, which carries fuel back to the
fuel tank from the engine; and the fuel emission
line, which carries HC gas (vaporized gasoline)
from the inside of the fuel tank back to the charcoal
canister. They usually run under the floor pan
or the frame. To avoid damage to the lines by
stones flying up from the surface of the road, a
protector is also provided.
Due to engine vibration, rubber hoses are used
where the fuel line connects with the carburetor
and the fuel pump.

FUEL FILTER

A fuel filter is located between the fuel tank and
fuel pump to remove any dirt or water that there
may be in the gasoline.
The element inside the filter reduces the flow
speed of the fuel, causing the water, and the dirt
particles that are heavier than gasoline, to settle
to the bottom; the particles of dirt that are lighter
than gasoline are filtered out by the element.

FUEL PUMP

There are two types of fuel pump, the type with a

return pipe and the type without a return pipe.
However, the basic construction and operation of
these two types are the same.
In most previous engines, the fuel was returned to
the fuel tank from the carburetor. Now, however, it
is usually returned from the fuel pump via the fuel
return line.

CHARCOAL CANISTER
(some models only)

The charcoal canister temporarily absorbs fuel
vapors (HC) from the carburetor float chamber,
and fuel vapors exhausted from the emission tube
when the pressure in the fuel tank rises due to increases
in the temperature into it internal canister
to prevent them from being exhausted.
The fuel vapors which are absorbed by the charcoal
canister are directed from the intake manifold
to the combustion chamber for burning when
the engine is running. Decreases in the ambient
temperature also result in lowering of the pressure
inside the fuel tank, causing the fuel vapors in the
canister to be drawn back into the fuel tank to
prevent them from being exhausted.