OPERATION
There a re several modes of opera tion for the Com-
mon Rail Diesel In ject ion System .
Pre-injection The pu rpose of th e pr e-injection fun c-
tion is t o r educe noise an d pollutants. The coolant
temper ature, charge a ir temper atur e a nd atmo-
spheric pressure a re use t o cor rect t he quan tity of
pilot injection. The qua ntity of pilot injection now
determ ined is deducted from the qua ntity of m ain
injection in or der to est ablish wh ether sufficien t
quan tity is a vailable for the followin g main inject ion.
The rail pressure is chosen sufficient ly h igh so t hat
a minimum qua ntit y is injected. If the quantity of
main injection is t oo small t he pilot in ject ion is
switch ed off by t he ECM.
The sta rt of a ctua tion of pilot injection is calcu-
lat ed dependen t on opera tin g point, the following
da ta being t aken int o accoun t:
Sh utting Off Pre-injection The pre-injection is sh ut
off when :
• Th e momen t of pre-in ject ion is exceeded
• Engine speed too high
• Pre-injected qu antity too low
• Ma in in jected quan tity too low
• Insufficient fuel rail pressure
• Engine is switched off
Calcu lat ing P re-in ject ion Quantity The pr e-injec-
tion qu antity is calcula ted on th e basis of:
• Engine speed
• Atmospher ic pressure
• Coolant temperatur e
• Boost a ir temper ature
• Fuel rail pressure
Main In jection Th e purpose of main injection fun c-
tion is t o en able the injection time an d injection
period calcu lated by th e ECM. The injection quan tity
required by th e engine is divided into the per-in jec-
tion a nd main injection quantit y. If th e main injec-
tion quan tity com pu ted by the ECM is too small, no
pr e-injection takes pla ce.
Start of Actuation
The st art of actu ation of ma in injection is depen-
dent on engine speed a nd qu antity. In a ddition , it is
correct ed dependin g on the following values:
• Coolant temperatur e
• Boost a ir temper ature
• Atmospher ic pressure
• Pre-injection correct ed YES/NO
Fig. 1 FUEL SUPPLY
1 - HIGH PRESSURE FUEL PUMP 8 - FUEL INJECTOR
2 - FUEL FROM LOW PRESSURE PUMP 9 - HIGH PRESSURE FUEL FROM HIGH PRESSURE PUMP
3 - FUEL FILTER 10 - FUEL PRESSURE SOLENOID
4 - LOW PRESSURE FUEL PUMP 11- FUEL RAIL
5 - FUEL TANK 12 - FUEL RAIL PRESSURE SENSOR
6 - RETURN FUEL 13 - FUEL QUANTITY CONTROL VALVE
7 - HIGH PRESSURE FUEL FROM HIGH PRESSURE PUMP 14 - FUEL TEMPERATURE VALVE
VA FUEL DELIVERY 14 - 7
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