(Purging Function - GF47.30-P-3015MMK)
Engine 276.9 In Model 222
Schematic diagram of fuel tank aeration and ventilation
Purging function requirements, general points
- Circuit 87M (Engine management ON)
- Engine started for 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 the following sensors:
- Coolant temperature sensor (B11/4)
- Intake air temperature sensor (B17)
- Intake manifold intake air temperature sensor (B17/1)
- Pressure sensor downstream of throttle valve (B28/7), engine load
- Crankshaft Hall sensor (B70), engine speed
- LH and RH oxygen sensor elements upstream of catalytic converter (G3/3b1, G3/4b1)
Function sequence for purging
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 here flow to the activated charcoal canister, where they are stored and from where they are extracted into the 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.
The purging switchover valve is actuated by the ME-SFI [ME] control unit at the ground end to regulate the purging quantity by means of an electric signal between 0 and 500 mA.
The purging quantity is determined through regulation of the opening cross-section of the purging switchover 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 vapor load in the activated charcoal canister.
| Electrical function schematic for purging function | PE47.30-P-2052-97SEC | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MMK |