Purging System

TASK
Checking the evaporative emission control system for function of the components and leakages.

Design:

75 Fuel tank
77 Activated charcoal filter
A Activated charcoal filter - purge control valves line
B Purge control valves - EA/CC/ISC actuator lines
D Fuel tank - activated charcoal filter line
E Air admission pipe
B4/4 Purge monitoring pressure sensor
M16/3 Right EA/CC/ISC actuator
M16/4 Left EA/CC/ISC actuator
N3/11 Left ME-SFI control module
N3/12 Right ME-SFI control module
Y58/2 Left purge control valve
Y58/3 Right purge control valve

FUNCTION
The check of the evaporative emission control system is carried out if the following conditions are met simultaneously:
- No fault in electrical actuation of purge control valves
- Actuation of purge control valves with an ON/OFF ratio between about 40-60%.

If all the conditions are met, the ME-SFI control module (engine 120: N3/12) detects the pressure in the pipe from the activated charcoal filter to the purge control valves from the purge monitoring pressure sensor (B4/4).

The pressure pattern in the pipe varies in accordance with the pulsed actuation of the purge control valves.

The ME-SFI control module monitors these variations in pressure for about 4s. If the pressure levels are less than about 50 bar apart, a fault is detected.

At higher elevations an altitude correction is conducted (e.g. pressure variations of about 11 bar are permissible at more than 2400 meters).