Purging Function - GF47.30-P-3015MNA
Engine 177.9 in model 205, 253
Engine 177.9 in model 213
up to model year 2021
Schematic diagram of fuel tank aeration and ventilation
Function requirements, general
- Engine start for at least 60 to 80 s
- Coolant temperature above 40°C
- Engine not in deceleration mode
- Engine not in the lambda adaptation phase
Purge control
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 later taken for combustion in the engine.
In order to enable the purging, the ME-SFI [ME] control unit (N3/10) reads in signals from the following components:
- Coolant temperature sensor (B11/4)
- Left charge air temperature sensor (B17/14)
- Right charge air temperature sensor (B17/15)
- Pressure sensor downstream of left throttle valve (B28/22)
- Pressure sensor downstream of right throttle valve (B28/23)
- Crankshaft Hall sensor (B70)
- Left oxygen sensor upstream of catalytic converter (G3/3)
- Left oxygen sensor sensor element upstream of CAT (G3/3b1)
- Right oxygen sensor upstream of catalytic converter (G3/4)
- Right oxygen sensor sensor element upstream of CAT (G3/4b1)
The fuel tank is vented (operational venting) via the aeration/vent valves, appropriate lines and the activated charcoal canister. The fuel vapor flows into the activated charcoal canister, where it is stored. When the engine is running, the ME-SFI [ME] control unit enables purging, and actuates the purging switchover valves. The purging quantity is defined via the opening cross-sections of the purging switchover valves. The ME-SFI [ME] control unit actuates the purging switchover valves with a current of 0 to 500 mA. The fuel vapor to be purged is then taken for combustion.
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 depending on the level of fuel vapors load in the activated charcoal canister.
Purging when idling
When the vehicle is idling, the fuel vapors stored in the activated charcoal canister are suctioned off by the existing vacuum via the purging switchover valves, the partial load operation check valves and the idling purge lines downstream of the throttle valves and combusted in the engine.
Wide open throttle purging
During wide open throttle operation, the fuel vapors stored in the activated charcoal canister are suctioned off via the wide open throttle operation check valves and the wide open throttle purge lines. The vacuum that is required for this is generated by a Venturi nozzle. The fuel vapors are routed via the wide open throttle purge lines, the turbochargers and the charge air coolers to the charge air distributors.
Schematic representation of purging
| Electrical function schematic for purge control | Engine 177.9 in model 205, 253 | PE47.30-P-2052-97FBD | |
| Engine 177.9 in model 213 up to model year 2021 | PE47.30-P-2052-97DBG | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 177.9 in model 205, 253 | GF07.70-P-9998MNA | |
| Engine 177.9 in model 213 up to model year 2021 |
GF07.70-P-9998MNE |