Overrun Mode Fuel Shutoff, Function - GF07.10-P-1014OGF

Engine 642.8 in model 166 

as of model year 2016 

Engine 642.8 in model 292 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87 (Engine management ON)
• Engine runs
• Vehicle rolling
• Accelerator not operated
• Selector lever position "D" or "R"
• Vehicle not in cruise control or DISTRONIC PLUS mode (vehicles with DISTRONIC PLUS)

Deceleration fuel shutoff, general 

Deceleration fuel shutoff in deceleration mode of the engine has the following tasks:

• increasing the braking effect of the engine
• reducing fuel consumption
• improving exhaust characteristics

The CDI control unit (N3/9) performs a deceleration fuel shutoff depending on the following signals:

• Coolant temperature sensor (B11/4)
• Accelerator pedal sensor (B37), accelerator pedal position
• Crankshaft Hall sensor (B70), engine rpm
• Fully integrated transmission control unit (Y3/8n4), gear range via drive train CAN (CAN C)

Deceleration fuel shutoff, function sequence 

If the accelerator pedal is not actuated (zero quantity delivery), deceleration mode is triggered. In decel mode, the CDI control unit switches off the fuel injectors for cylinders 1 to 6 (Y76/1 to Y76/6) as a function of the coolant temperature, engaged gear and at an engine speed > 1600 rpm.

The CDI control unit also lowers the fuel pressure in the rails over the pressure regulating valve (Y74). Upon operation of the accelerator pedal or a drop in the engine rpm to < 1600/min, the CDI control unit again actuates the fuel injectors and increases the fuel pressure in the rails over the quantity control valve (Y94) or the pressure regulating valve, dependent on the Model of regulation.

If the conditions for teaching in the injector zero quantities are fulfilled, the fuel pressure in the rail can, however, be increased up to 1, 000 bar in decel mode.