13B-12V12 MR-372-J84-13B300$030.mif
DIESEL INJECTION
Fault finding – System operation13B
EDC16CP33
Program No.: C4
Vdiag No.: 04, 08, 18, 1C,
20, 24, 26, 28, 34, 38, 44,
4C, 54, 58, 5C, 60, 62, 74
a. The computer:
Determines the injection pressure value necessary for the correct operation of the engine; the pressure can reach
1600 bar in the rail and it must be constantly regulated.
Checks that the pressure value is correct by analysing the value transmitted by the pressure sensor located on
the rail.
Determines the injection duration required to deliver the right quantity of diesel fuel and the moment when injection
should start. Controls each injector electrically and individually after determining these two values.
The quantity of fuel injected is determined by:
– Engine speed (Crankshaft + Cam for synchronisation).
– Accelerator pedal.
– Turbocharging pressure.
– Coolant temperature,
– Inlet air temperature.
–Air flow
– Pressure in the rail.
– Vehicle speed.
The computer manages:
– idling regulation,
– exhaust gas flow reinjection to the inlet,
– fuel supply check (advance, flow and rail pressure),
– the fan assembly control,
– the air conditioning (cold loop function),
– cruise control/speed limiter function,
– pre-post heating control,
– indicator lights control via the multiplex network,
– the operation of the catalysed particle filter,
– turbocharging pressure.
The high pressure pump is supplied at low pressure by an integrated low pressure pump (transfer pump).
It supplies the rail, the pressure in which is regulated by:
–the pressure regulator on the rail (DRV) for starting phases, starting the engine when cold (increase in
temperature to heat the diesel circuit) and when throttling-off,
–the pressure regulator on the pump (MPROP) for all other phases (90% of cases).
As natural leaks in piezoelectric injectors are very low, opening the pressure regulator (DRV) is the only quick
method of dumping the rail pressure and it prevents overpressure when injection is restarted.
The pressure regulator on the pump (MPROP) enables the high pressure pump to supply just the exact quantity
of diesel fuel required to maintain the rail pressure. This component minimises the heat generated and improves
engine output.
Note:
Each piezoelectric injector is connected to the return rail. The injector return rail is kept pressurised by a
mechanical valve at the end of the return rail with a 10 bar calibration (by comparison, solenoid injectors used to
return directly into the common fuel return circuit). This feature is linked to the operation of piezoelectric injectors.
