The document discusses the function and types of fuel injectors, detailing their components and operations for optimal fuel atomization and distribution. It highlights various injector types, including mechanical, electronic, and two-stage injectors, along with the specific designs of nozzles used for different engine requirements. Additionally, it addresses testing procedures for injectors and trouble-shooting methods for common issues encountered with fuel injectors.

1. INJECTORS

2. FUNCTION OF INJECTOR
• To (maintain) built up fuel high pressure.
• To inject the fuel in good atomized and uniformly shape.
• After injection clean cut off.
• Distribution of fuel for maximum mix with air.

3. TYPE OF INJECTORS
MECHANICALLY
OPERATED
HYDRAULICALLY /
AUTOMATIC
OPERATED
ELECTRONIC
(CRDI)
MICO BOSCH LUCAS INJECTOR
PT INJECTOR UNIT
INJECTOR

4. MECHANICAL ELECTRONIC HYDRAULIC

5. TYPE OF INJECTOR
NOZZLE
SINGLE HOLE MULTI HOLE
SHORT-STEM
MULTI HOLE
PINTLE TYPE PINTAUX TYPE
LONG-STEM
MULTI HOLE
VCO

6. HOLE TYPE PINTLE TYPE

7. INJECTOR HYDRAULIC
NOZZLE SEAT
FUEL INLET PASSAGE
NOZZLE VALVE
NOZZLE
NOZZLE
VALVE
SEAT
FUEL INLET PASSAGE
VALVE R. SPRING

8. INJECTOR NOZZLE FUEL FLOW:-
Injection nozzle are simply hydraulic valve operated by
fuel pressure. Fuel flow generated by the injection pump enters the
nozzle holder at the fuel inlet and proceed down the fuel inlet and into
the annular area of the valve. When the pressure of fuel against the
annular area of the needle valve exceed the preset pressure of the
pressure spring, the needle valve is raised from its seat then a metered
amount of fuel is injected through the orifice on a hole type nozzle or
by the pintle on a pintle-type nozzle and into combustion chamber.
During the operation a small amount of fuel will leak through the
needle valve to help lubricate and cool the injector nozzle. This fuel
accumulates in the pressure spring area and return to the fuel tank by
a fuel return line.

9. PINTLE TYPE

10. HYDRAULIC INJECTOR:-
According to injector nozzle shape hydraulic injector are
further divided into three parts :
SINGLE HOLE TYPE:–
These nozzle are used in an engine designed with pre
combustion chamber. Where the fuel is injected into a narrow
conical shaped chamber outside the main cylinder the pressurized
air fuel enter into the cylinder.

11. TWO-STAGE INJECTOR
INTRODUCTION:-
With some DI systems, significant engine noise is
generated during combustion. The two stage injector has been
designed to combat this problem. An initial low rate of fuel
injection, followed by injection at a higher rate, reduce the rate
of combustion pressure rise, and hence the peak cyl pressure.
This results in a significant reduction in noise, without loss of
power.
During injection, a conventional needle valve lifts until the
shoulder of the valve about the pressure face of the nozzle
holder or adaptor plate. With two stage injection, the needle
valve initially lifts to an intermediate position and hence stops.
Further movement to the full-lift position does not occur until

12. TWO-STAGE INJECTOR:-
1,SECONDARY SPRING 2, UPPER SPRING SEAT
3, SPINDLE 4, PRIMARY SPRING
5, LOWERSPRING SEAT

13. FUNCTION OF TWO-STAGE INJECTOR:-
The two-stage injector works in principle like a low-spring
injector ,except that are two nozzle springs in ‘series’ and set to
operate at different pressures. They are known as the ‘primary’
spring and the ‘secondary’ spring.
As pumping pressure rises, the pre-load on the primary spring
is exceeded and the needle valve lifts, together with the lower spring
seat and spindle, until the spindle abuts the upper spring seat.
During this period a small quantity of fuel is injected.
As pumping pressure continues to increase, the pre-load on
the secondary spring is exceeded and the needle valve rises to the
full-lift position, allowing the main charge of fuel to be injected at an
increased rate.

14. • MULTI HOLE NOZZLES
In cylinder head design because of the small tip
diameter. Low emission types have been designed for use with
direct injection engines, these are divided into two further
categories : long stem and short stem. These nozzles inject the fuel
directly into the cylinder, with a combustion chamber formed in the
top of the piston. The range of multi – hole nozzles includes:
1,SHORT–STEM MULTI HOLE :-
Traditional nozzle construction. Mainly used with
high spring holders.
2,LONG–STEM MULTI HOLE :-
These are used on current engine constructions and
allow more flexibility introduced to meet future requirements.

15. Valve covered orifice nozzle (vco):-
This is a version of the low emission long-stem
nozzle where the needle valve covers the injection holes
when it closes, rapidly stopping the fuel flow. The “sac” in
previous designs is also eliminated, so preventing the
retention of fuel between the closed needle valve and the
injection holes, further reducing exhaust emissions.

16. INJECTOR TESTS
B- BREAKING PRESSURE TEST OPENING PRESSURE TEST
A- ATOMIZATION TEST
D- DRIBBLING TEST
L - LEAK OFF TEST

17. 1,BREAKING PRESSURE / OPENING PRESSURE TEST
Mount the injector on the test bench and open stop valve,
gradually operate the handle. Note the reading on pressure
gauge, when fuel just comes out from injector nozzle. Peak
reading shown on gauge is the breaking pressure.
In some injectors provision is made to adjust the breaking
pressure by increasing or decreasing the number of shims
located behind the pressure spring. While in some cases an
adjusting nut is provided for adjusting the breaking pressure.

18. 2. ATOMIZATION TEST
Close stop valve and operate the handle with the recommended
speed. The fuel will come out from the injector nozzle in
atomized shape and must be uniform.

19. 3.DRIBBLING TEST
Open stop valve and gradually operate the handle and build up
fuel pressure just below breaking pressure. Hold the operating
lever for the specified time given by the manufacturer and note
the number of fuel drops coming out from the nozzle. It must be
within the limit of manufacturer’s specification. Generally it
should be not more than one to two drops within ten seconds.
4.LEAK OFF TEST
Gradually operate the operating lever and build up the fuel
pressure just below the breaking pressure. Hold the operating
lever, note the fuel pressure drop in pressure gauge. It must be
not more than the makers specification.

20. IDENTIFICATION OF INJECTOR NOZZLE
Injector nozzles are identified by a series of letter and numbers on the body.
Example kbal100sc2/13 would mean :
Kb - type of nozzle holder (flange type)
A - spring location
L - long nozzle
100 - Installation length in mm
S - Shoulder diameter, which must match the
shoulder diameter of the nozzle
C - nozzle locating pin placement when used
2/13 - application information

21. TROUBLE SHOOTING IN INJECTOR
Fault Possible cause Remedy
Excessive
leak-off
Dust particle between pressure face
of the nozzle, spring retainer or plate
and nozzle holder
Clean nozzle
Loose nozzle holder Inspect
Nozzle
bluing
Faulty installation or tightening
insufficient cooling
Replace nozzle
Correct cooling system
Nozzle
opening
pressure too
high
Incorrect shim adjustment Replace nozzle
Nozzle valve dirty or sticky or
opening clogged
Clean nozzle
Seized nozzle Replace nozzle

22. TROUBLE SHOOTING IN INJECTOR
Fault Possible cause Remedy
Nozzle
opening
pressure too
low
Incorrect shim adjustment
Nozzle valve spring broken
Readjust nozzle
Replace spring and
readjust pressure
Nozzle seat worn Install new or
reconditioned nozzle
Nozzle drip Nozzle leaks because of carbon
deposit or sticking nozzle valve
Clean nozzle
Defective nozzle Replace nozzle
Spray pattern
distorted
Carbon deposit on tip of nozzle valve Clean nozzle
Nozzle hole partially blocked Clean nozzle
Defective nozzle Replace nozzle
Nozzle valve dirty or sticky or
opening clogged
Clean nozzle
Seized nozzle Replace nozzle