Purging Function - GF47.30-P-3015MMG

ENGINE 276.9 in MODEL 166 up to model year 2016 

Schematic diagram of fuel tank aeration and ventilation (except code 494 (USA version)) 

Purging function requirements, general points 

• Circuit 87M (engine management ON)
• Engine started for at least 45 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.

For enabling of purging, the ME-SFI [ME] control unit (N3/10) reads in signals from the following components:

• Coolant temperature sensor (B11/4), coolant temperature
• 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 rpm
• Left and right oxygen sensors upstream of catalytic converter (G3/3, G3/4)

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 extracted through the purging switchover valve and combusted in the engine.

To control the purge quantity, the ME-SFI [ME] control unit actuates the purging switchover valve at the ground end with a pulse width modulated signal at a frequency of 10 to Hz.

The purge quantity is determined by continuously opening and closing the purging switchover valve with on-periods of varying durations.

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.

	Electrical function schematic for purge control		PE47.30-P-2052-97NAE
	Overview of system components for gasoline injection and ignition system with direct injection		GF07.70-P-9998MMG