1. The common rail fuel injection system has low-pressure and high-pressure circuits to transport fuel and generate high injection pressures, controlled by an ECU and sensors. 2. The low-pressure circuit cleans and moves fuel to the high-pressure circuit where a pump pressurizes the fuel up to 1,350 bar in a rail tank for storage. 3. The ECU uses sensor readings to calculate injection values and trigger the injectors to inject precise amounts of fuel at optimal times from the constant-pressure rail tank.

1. COMMON RAIL DIRECT INJECTION
SYSTEM

2. Demand On Modern Diesel Engine
Development
 Low fuel consumption
 Low pollutant emissions
 Quiet running engines
 Improved engine performance

3. Common rail fuel injection system and its
function
 Provide the diesel engine with fuel
 Generate the high pressure needed for fuel
injection and distribute the fuel to the
individual cylinders
 Inject precisely correct amount of fuel at
exactly the right moment in time.
 In contrast to other injection system Common
rail fuel injection system is an accumulator
injection system.

4. How does a CR system function?

5. Low –pressure circuit comprises of:
Fuel tank ,Pre-supply pump, Fuel filter, And the
respective connection lines.
The Common Rail Sub functions

6. Low –pressure circuit
The low –pressure circuit is responsible for
transporting the fuel to the high –pressure circuit

7. High –pressure circuit comprises:
High – pressure pump with pressure – control valve
The high – pressure accumulator (Rail )with the rail –
pressure sensor
Injectors, and
The respective high – pressure connection lines.
The Common Rail Sub functions

8. The high – pressure circuit
It is the responsibility of the high
pressure circuit to generate a constant
unvarying high pressure in the high
pressure accumulator (the rail) and to
inject the fuel through the injectors into
the engine’s combustion chambers.

9. ECU and sensors
The common rail ECU evaluates the signals from the
following sensors.
Crankshaft – speed sensor, Camshaft sensor,
Accelerator-pedal travel sensor
The Common Rail Sub functions

10. The common rail ECU evaluates the signals from the
following sensors:
Boost – pressure sensor, Air temperature sensor,
Air – mass meter, and Rail pressure sensor.
The Common Rail Sub functions

11. The Common Rail Sub functions
ECU and sensors
The sensor are responsible for measuring important
physical quantities. The ECU calculates injected fuel
quantity, start of injection, duration of injection, and
rate of discharge curve, as well supervises the correct
functioning of the injection system as a whole.

13. High- pressure accumulator (Rail)
Store fuel
Prevent pressure fluctuations

14. Rail is a forged-steel tube.
ID is approx.. 10mm
Length is between 280 and 600mm
The volume must be “ as small as possible,
as large as necessary”
High- pressure accumulator (Rail)

15. The injector is equipped with:
2/2 electromagnetic servo valve
Nozzle
Valve control chamber
Return line
Injector

16. The essential forces for correct functioning are:
 Nozzle-spring force
 Valve spring force
 Electromagnet force
 Force due to the pressure in the valve-control
chamber
 Force due to the pressure in the nozzle needle
Injector

17. ECU with sensors
Common Rail is an EDC controlled injection
system
The ECU controls & monitors the complete
injection process
The sensors delivers all the measured values
which are required in the process

18. Summary
Components of CRFIS
are:
 Pre-supply pump
 High-pressure pump
 High-pressure
accumulator(rail) Pressure-control valve
Rail-pressure sensor
Injectors
ECU with sensors
COMMON RAIL FUEL INJECTION SYSTEM

19. COMMON RAIL FUEL INJECTION SYSTEM
SUMMARY
1.The basic functional groups of the common rail are : low
– pressure circuit , high – pressure circuit ECU and
sensors.
2.In the low – pressure circuit, the fuel is cleaned by a filter
and then transported to the high – pressure circuit
COMMON RAIL FUEL INJECTION SYSTEM

20. SUMMARY
3.In the high – pressure circuit , the maximum
pressure of 1,350 bar is generated in the high –
pressure accumulator (Rail).
The pressure is maintained at a constant
level , and the fuel is taken from the rail every
time an injection takes place.
4.The ECU controls and monitors the complete
injection system. Using the signals from the
sensors, the ECU calculates all the values for
the injection process and triggers the
components in high-pressure circuit (pressure –
control valve, injectors).