Purging function - GF47.30-P-3015MIG

MODEL 251.054/154 with ENGINE 272.945 as of model year 2009/CY 08 

MODEL 164.186 with ENGINE 272.967 as of model year 2009/CY 08 model refinement package 

MODEL 251.056/065/156/165 with ENGINE 272.967 as of model year 2009/CY 08 

MODEL 164.871 with ENGINE 273.923 as of model year 2009/CY 08 

MODEL 164.172 with ENGINE 273.963 as of model year 2009/CY 08 model refinement package 

MODEL 164.886, 251.072/172 with ENGINE 273.963 as of model year 2009/CY 08 

Purging function requirements, general 

• Circuit 87M ON (engine control 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 

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:

• Hot film MAF sensor (B2/5), engine load
• Intake air temperature sensor (B2/5b1)
• Coolant temperature sensor (B11/4)
• Crankshaft Hall sensor (B70), engine speed
• LH and RH O2 sensors upstream of ME-SFI [ME] control unit(G3/3, G3/4), oxygen sensor signals

Purging function sequence 

The fuel tank is ventilated through the safety valve (rollover valve), the aeration/vent line 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 (Y58/1) 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 (PWM signal) (with a frequency of 10 Hz). The purge quantity is determined by continuously opening and closing the purge control valve with on-times of varying duration.

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 164		PE47.30-P-2052-97MAA
		Model 251		PE47.30-P-2052-97RAA
	ME-SFI [ME] control unit, component description	N3/10	Engine 272	GF07.61-P-6000MIG
		N3/10	Engine 273	GF07.61-P-6000MLG