Purging function - GF47.30-P-3015MI
ENGINE 272.9 (except 272.982) in MODEL 204.0/2 as of model year 2009
ENGINE 272.9 (except 272.983) in MODEL 212
ENGINE 272.9 (except 272.984) in MODEL 207
ENGINE 272.9 in MODEL 204.9
ENGINE 273.9 in MODEL 207, 212
Schematic diagram (except code (494) USA version)
Purging function requirements, general points
- Circuit 87M ON (engine control ON)
- Engine started for at least 45 s
- Coolant temperature > 40°C
- Engine not in deceleration mode
- Engine not in the lambda adaptation phase
Purging, general points
When the fuel tank is being ventilated, no fuel vapors should escape into the outside air.
The fuel vapors are stored in the activated charcoal canister and burnt later in the engine.
In order to enable the purging, the ME-SFI [ME] control unit (N3/10) reads in the following sensors:
- hot film MAF sensor (B2/5), engine load
- intake air temperature sensor (B25b1)
- coolant temperature sensor (B11/4)
- crankshaft Hall sensor (B70), engine speed
- Left and right oxygen sensors upstream of catalytic converter (G3/3, G3/4)
Function sequence for purging
The fuel tank is ventilated through the aeration/vent valves, the aeration/vent line and the activated charcoal canister.
The fuel vapors flow to the activated charcoal canister where they are stored, and drawn off into the variable intake manifold when purging is enabled.
When the engine is running, the fuel vapors stored in the activated charcoal canister are drawn off through the purging switchover valve and combusted in the engine.
To control the purge quantity, the ME-SFI [ME] control unit actuates the purging switchover valve at the ground end with a pulse width modulated signal (PWM signal) (with a frequency of 10 Hz).
The purge quantity is determined by continuously opening and closing the purge control valve with on-times of varying duration.
The idle speed control prevents the purging from causing a change in rpm when the engine is at idle. The fuel-air mixture is leaned out according to the level of fuel vapor charge in the activated charcoal canister.
| Electrical function schematic for purging function | MODEL 204 | PE47.30-P-2052-97FAB | |
| MODEL 207 | PE47.30-P-2052-97EAB | ||
| MODEL 212 | PE47.30-P-2052-97DAB | ||
| Overview of system components motor electronics (ME-SFI) fuel injection and ignition system | GF07.61-P-9997MI |