Purging Function - GF47.30-P-3015MRD
Engine 274.9 in model 213, 238
up to model year 2021
Schematic diagram of fuel tank aeration and ventilation (except code 494 (USA version))
Function requirements, general
- Engine start before at least 60 to 80 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 signals from the following sensors:
- Pressure in wide open throttle purge line (with code 494 (USA version))
Purging pressure sensor (B4/4)
- Coolant temperature
Coolant temperature sensor (B11/4)
- Charge air temperature
Charge air temperature sensor upstream of throttle valve (B17/7) Charge air temperature sensor downstream of throttle valve (B17/9)
- Engine load
Pressure sensor downstream of throttle valve (B28/7)
- Engine speed
Crankshaft Hall sensor (B70)
- Nitrogen oxide and oxygen concentration in exhaust gas Oxygen sensor downstream of catalytic converter (G3/1)
- Oxygen sensor, sensor element downstream of catalytic converter (G3/1b1)
Oxygen sensor upstream of catalytic converter (G3/2)
- Oxygen sensor, sensor element upstream of catalytic converter (G3/2b1)
Ventilation of the fuel tank (operational ventilation) takes place over the aeration/vent valves, the aeration/vent lines and the activated charcoal canister. The fuel vapors flow to the activated charcoal canister where they are stored and drawn off into the charge air distributor when purging is enabled.
When the engine is running, the fuel vapors stored in the activated charcoal canister are extracted through the purging switchover valve and combusted in the engine. The purge quantity is controlled by the ME-SFI control unit operating the purge control valve. The quantity of intaken fuel vapors is determined via the regulation of the opening cross-section of the purge control valve.
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.
The purging is divided into the following subfunctions:
- Purging when idling
- Wide open throttle purging
Purging when idling
In idle, the fuel vapors stored in the activated charcoal canister are drawn off by the existing vacuum via the purge control valve, the partial load operation check valve and the idle purge line behind the throttle valve and burnt in the engine.
Wide open throttle purging
In wide open throttle operation the fuel vapors are suctioned off through the wide open throttle operation check valve and the wide open throttle purge line. The vacuum required for this is generated by a Venturi nozzle. The fuel vapors are then routed over the wide open throttle purge line, the exhaust gas turbocharger and the charge air cooler to the charge air distributor.
Schematic representation of purging
| Electrical function schematic for purge control | PE47.30-P-2052-97DBD | ||
| Overview of system components for gasoline injection and ignition system with direct injection | Engine 274.9 in model 213 (except 213.050/053/153), 238 up to model year 2021 | GF07.70-P-9998MRD | |
| Engine 274.9 in model 213.050/053/153 up to model year 2021 | GF07.70-P-9998MRP |