1.
CHAPTER – 3
FUEL FEED SYSTEMS

2.
TYPES OF FUEL SUPPLY SYSTEM

3.
GRAVITY FEED SYSTEM :-
 In this system the petrol is supply to the engine by gravitational force.
 In this system the level of fuel is high than engine, due to the level tank the petrol will automatically supply by
gravitational force this system is having fuel tank, cock, filter, and carburetor .
 The cock is very important in this system because there is a possibility of leakage the cock is having three position
that is on, off and reserve.
 This system used in two wheeler and three wheeler.
PRESSURE FEED SYSTEM :-
 In this system the petrol is supplied with pressure by fuel pump.
 In this system the fuel tanks is fitted at lover level of engine so that petrol cannot flow automatically hence fuel pump
is used.
 The fuel pumps suck the fuel from tank and give the pressure to petrol and supply to engine.
 It this system the parts use are :- (1) fuel tank (2) fuel pump (3) filter (4) MPFI (5) pipe line.
 this system used in four wheeler.
TYPES OF FUEL SUPPLY SYSTEM

4.
FUEL
TANK
FUEL
FILTER
CARBURETTOR
FUEL
PUMP
COMPONENTS OF FUEL SUPPLY SYSTEM

5.
AC MECHANICAL FUEL PUMP

6.
ELECTICAL FUEL PUMP

7.
AIR CLEANER
The fuel system mixes air and fuel to produce a combustible mixture. A large volume of air passes through
the carburetor or fuel injection system and engine, as much as 100,000 cubic feet of air every 1,000 miles.
Air always contains a lot of floating dust and grit. The dust and grit could cause serious damage if they
entered the engine. To prevent this, mount an air cleaner at the air entrance of the carburetor or fuel
injection system. The two types of cleaners currently used are the wet and dry types.
•The wet-type. or oil bath, air cleaner consists of the main body, the filter element that is made of woven
copper gauze, Incoming air enters between the cover and the main body. The air is pulled down to the
bottom of the main body where it must make a 180-degree turn, as it passes over the oil reservoir.
•As the air passes over the oil reservoir, most of the particles will not be able to make the turn, and they
will hit the oil and be trapped.
•As the air continues upward and passes through the filter element, the smaller particles that bypassed the
oil will be trapped.
•The air keeps the element soaked with oil by creating a fine spray, as it passes the reservoir.
AIR CLEANER

8.
TYPES OF AIR CLEANER

9.
DRY TYPE AIR CLEANER
 The dry-type air cleaner passes the incoming air
through a filtering medium before it enters the
engine.
 The air filter contains a ring of filter material (fine-
mesh metal threads or ribbons, pleated paper,
cellulose fiber, or polyurethane, These types of filter
materials provide a fine maze that traps most of the
airborne particles.
 dry-type air cleaners may use a metal-
gauze or paper filter element.
 Swirling motions and sudden changes in the
direction of airflow separate the dust from the air.
 Air first enters an outer chamber around the
 filter element and is then filtered through small holes
in the element before entering the carburetor.

10.
The oil bath air filter pulls in outside air and
makes it turn 90 degrees over a pool of oil. This
helps to remove the large, heavy particles. The
air then travels over a filter element that rests in
the oil and wicks it into the fibers (often made
of steel mesh). Some early filters used horse
hair for the element, while some more modern
filters used foam.
WET TYPE AIR
CLEANER

11.
WET TYPE AIR CLEANER
OIL WETTED TYPE
It has a wire mesh as a filtering element which is coated
with an oil film. The filtering element is fitted at the
entrance of air coming passage and removes the dust
particles deposit in the oil film.This helps to remove the
large, heavy particles. The air then travels over a filter
element that rests in the oil and wicks it into the fibers
(often made of steel mesh). Some early filters used horse
hair for the element, while some more modern filters used
foam.

12.
CABURETTOR
•In S. I. engine, air and fuel are mix
outside the engine cylinder and then
supplied to cylinder for burning of fuel
with the help of spark plug for
producing power.
•Carburetor is device which mixes the
air and fuel, this device is fitted on inlet
manifold.

13.
FUNCTION OF CARBURETOR
 It maintained the constant head of petrol in float chamber that means is help supply the constant petrol to
engine.
 It provides mixture required at a different speed and load of the engine.
 It provides a mixture in starting condition.
 It provides a mixture idling condition.
 It provides required mixture at the time of acceleration.
 S.I. Engine requires varying mixture strength at different condition of engine.
 Example:- At the time of starting rich mixture is a required due to coldness of engine. That means the
mixture is having 12 parts of air part and one part of petrol at the time of idling lean mixture that starting is
required that may vary from 13:1 to 14:1 during partly throttle operation or normal running lean mixture is
required that is 15:1 to 16:1 like this engine run with different condition, so that carburetor designed in such
way that is can provided verging mixture strength at different condition of engine

14.
SIMPLE CARBURETOR
•The simple carburetor is a having a float
chamber and mixing chamber air from float
chamber is for supply the petrol at constant head
and supply it as per requirement of engine.
•It is a having float inside a float chamber that is
hallow, needle valve is fitted which maintains the
one way flow.
•It float chamber empty the petrol flows in side it
from fuel pump, as soon as petrol reaches
required level float come up and close the inlet
passage after some time when level of petrol
decreases float as well as needle comes down
with its self weight and inlet passage and petrol
stored in a float chamber like this constant level
is maintained by float chamber mixing chamber
or air horn is a simple tube which is having
reduced diameter at its center called venture in
that small tube is provided which is having a
nozzle jet at its one end and other end is
connected to the float chamber at the time of
engine starting when piston moves from T.D.C. to

15.
SOLEX CARBURETOR

16.
STARTING CIRCUIT
 The throttle valve remains in closed position during starting.
 The petrol is supplied to the starter petrol jet through the first
passage from the float chamber. And the air through the starter air
jet for starting operation.
 The position of various holes can be adjusted in front of starter
petrol jet by starter lever. Then air is mixed coming from starter air
jet.
 This air-fuel mixture passes through another hole of starter valve, in
a passage of the carburettor, below the throttle valve.
 The suction stroke of the engine sucks this mixture into the cylinder.
 This mixture is rich enough to start the engine. After the engine
starts and speed increases, a weak mixture is required.
 Hence a small hole of the starter valve is brought in front of the
starter petrol jet by means of starter lever.

17.
IDLING AND SLOW RUNNING CIRCUIT
 During the idling operation, the throttle valve is kept closed.
 While an engine receives the mixture through a port opening
below the throttle valve.
 Where area can be varied by an idle adjusting screw according to
the need of the engine.
 The petrol is supplied to a pilot petrol jet from the main jet fuel
circuit through a fourth passage and the air from a pilot air jet.
 The petrol and air thus supplied mix up in the idle passage.
 Then go to a port situated below the throttle valve from where
the mixture is sucked into an engine.
 During the slow running, the engine draws the mixture from the
idle passage through a hole.

18.
 At normal running speed, starting circuit is closed
and the throttle valve is opened.
 The normal running circuit consists of the main
jet which receives the petrol through the second
passage.
 This is done from the float chamber as the
throttle valve is opened sufficiently.
 The air is drawn through the venture where the
petrol mixes up with it.
 This forms a suitable mixture for the normal
running of the engine.
 In this case, only throttle valve governed the air-
fuel ratio.
NORMAL RUNNING CIRCUIT

19.
 The engine requires an extra rich mixture, during
acceleration period.
 To obtain an extra rich mixture, the fuel is pumped
under pressure into the main air passage.
 The diaphragm pump is used to create pressure,
which is actuated by a lever connected to the
accelerator.
 The pump sucks the petrol from the float chamber
through the pump valve.
 Then forces it through a third passage into the
main passage through an injector above the
venture of the carburettor.
ACCELERATING CIRCUIT