Purging function - GF47.30-P-3015MMC

MODEL 216.3, 221.0/1 with ENGINE 157.9

MODEL 216.3, 221.0/1 with ENGINE 278.9

Fig 1: Fuel Tank Aeration And Ventilation - Schematic Diagram

Courtesy of MERCEDES-BENZ USA

Schematic diagram of fuel tank aeration and ventilation

(except Code (494) USA version)

Purging function requirements, general points

Circuit 87M ON (engine control 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 the following sensors:

Coolant temperature sensor (B11/4)
Intake air temperature sensor (B17)
Pressure sensor downstream of throttle valve actuator (B28/7), engine load
Crankshaft Hall sensor (B70), engine speed
O2 sensors on the left and right, upstream of CAT (G3/3, G3/4)

Function sequence for purging

Ventilation of the fuel tank (operational ventilation) takes place over the aeration/vent valves, the aeration/vents 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 purge control valve and combusted in the engine.

The purging switchover valve is actuated by the ME-SFI [ME] control unit at the ground end by means of an electric signal between 0 and 500 mA to regulate the purge quantity.

Regulation of the opening cross-section of the purging switchover valve determines the purge quantity.

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 diagram for purging function	Model 216	PE47.30-P-2052-97CAH
Electrical function diagram for purging function	Model 221	PE47.30-P-2052-97SAH
Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MMB