Purging Function - GF47.30-P-3015KJ

ENGINE 281.910 in MODEL 453.0/3/4 

Purging function requirements, genera) points 

• Circuit 87 (Engine management ON)
• Engine start before at least 120 s
• Coolant temperature >70°C
• Engine not in decel mode
• Engine not in the lambda adaptation phase

Purging, genera) 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)
• Pressure sensor downstream of throttle valve (B28/7), engine load
• Oxygen sensor downstream of catalytic converter (G3/1)
• Oxygen sensor upstream of catalytic converter (G3/2)
• Crankshaft position sensor (L5), engine speed

Function sequence for purging 

Ventilation of the fuel tank (operating ventilation) takes place over the activated charcoal canister shutoff valve (Y58). The fuel vapors flow for a running engine to the activated charcoal canister where they are stored and drawn off into the charge air distributor when purging is enabled and burnt in the engine.

The purge quantity is determined by constantly opening and closing the fuel tank bleed valve with on periods of varying lengths.

The frequencies of the bleed valve are 8 Hz or 20 Hz. This is dependent on the engine rpm.

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-2052-97BBA
	Overview of system components motor electronics (ME-SFI) fuel injection and ignition system		GF07.61-P-9997KJ