Purging Function - GF47.30-P-3015MNL
Engine 176.9, 177.9 in model 217
Engine 176.9, 177.9 in model 222
Engine 177.9 in model 290
up to model year 2021
Schematic diagram of fuel tank aeration and ventilation
Purging function requirements, general points
- Circuit 87M (Engine management ON)
- Engine start before at least 60 to 80 s
- Coolant temperature > 40°C
- Engine not in overrun 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:
- Coolant temperature sensor (B11/4), coolant temperature
- Left and right charge air temperature sensors (B17/14, B17/15), charge air temperature
- Pressure sensor downstream of left and right throttle valve (B28/22, B28/23), engine load
- Crankshaft Hall sensor (B70), engine speed
- Left and right 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 vent/bleed valves, the vent/bleed 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 charge air distributor when purging is enabled.
When the engine is running, the fuel vapors stored in the activated charcoal canister are drawn off through the left and right purging switchover valves and combusted in the engine.
The left and right purging switchover valves are actuated by the ME-SFI [ME] control unit at the ground end to regulate the purging quantity using a current signal between 0 and 500 mA.
The volume of suctioned fuel vapors is determined through closed-loop control of the opening cross-section of the left and right purging switchover valves.
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.
Function sequence for purging
- Function sequence for neutral purging
- Function sequence for wide open throttle purging
Function sequence for neutral purging
In idling, the fuel vapors stored in the activated charcoal canister are suctioned off by the existing vacuum via the left and right purging switchover valves, the partial load operation check valves and the partial load purge lines behind the throttle valves and burned in the engine.
Function sequence for wide open throttle purging
In wide open throttle operation, the fuel vapors are suctioned off through the wide open throttle operation check valves and the wide open throttle purge lines.
The vacuum required for this is generated by a Venturi nozzle. The fuel vapors are then routed over the wide open throttle purge lines, ATLs and the charge air coolers to the charge air distributors.
| Electrical function schematic for purge control | Engine 177.9 in model 290 up to model year 2021 | PE47.30-P-2052-97XBA | |
| Engine 176.9, 177.9 in model 217 Engine 176.9, 177.9 in model 222 | PE47.30-P-2052-97SEL | ||
| Overview of system components for gasoline injection and ignition system with direct injection | GF07.70-P-9998MNL |