SSANGYONG KYRON 2007.04 Manual page 287

09-20
1491-01
▶ Detection of leaks in the cylinders
The accelerometer is also used to detect any injector which may have stuck open. The
detection principle is based on monitoring the ratio. If there is a leak in the cylinder, the
accumulated fuel self-ignites as soon as the temperature and pressure conditions are favorable
(high engine speed, high load and small leak).
This combustion is set off at about 20 degrees before TDC and before main injection.
The ratio therefore increases considerably in the detection window. It is this increase which
allows the leaks to be detected. The threshold beyond which a fault is signaled is a percentage
of the maximum possible value of the ratio.
Because of the severity of the recovery process (engine shut-down), the etection must be
extremely robust.
An increase in the ratio can be the consequence of various causes:
- Pilot injection too strong
- Main combustion offset
- Fuel leak in the cylinder
If the ratio becomes too high, the strategy initially restricts the pilot injection flow and retards the
main injection. If the ratio remains high despite these interventions, this shows that a real leak
is present, a fault is signaled and the engine is shut down.
Detection of an accelerometer fault
▶
This strategy permits the detection of a fault in the sensor or in the wiring loom connecting the
sensor to the ECU.
It is based on detection of the combustion. When the engine is idling, the detection window is
set too low for the combustion caused by the main injection. If the ratio increases, this shows
that the accelerometer is working properly, but otherwise a fault is signaled to indicate a sensor
failure. The recovery modes associated with this fault consist of inhibition of the pilot injection
and discharge through the injectors.
ENGINE D20DT
KYRON 2007.04