Purging function - GF47.30-P-3015MIS

MODEL 221.0 /1 with ENGINE 272.9 as of model year 2009 /YoM 08 

MODEL 216.3, 221.0 /1 with ENGINE 273.9 as of model year 2009 /YoM 08 

Schematic diagram of fuel tank aeration and ventilation 

Purging f unction 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 valves (rollover valves), the fuel retention valve 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 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 216		PE47.30-P-2052-97CAB
		Model 221		PE47.30-P-2052-97SAB
	ME-SFI [ME] control unit, component description	N3/10	Engine 272 except 272.974 (hybrid)	GF07.61-P-6000MIS
		N3/10	Engine 272.974 (hybrid)	GF07.61-P-6000MEH
		N3/10	Engine 273	GF07.61-P-6000MLS