Overrun Mode Fuel Shutoff, Function - GF07.10-D-1014TSA

Engine 651 in model 907 

Block diagram 

Function requirements for deceleration fuel shutoff, general points 

• Circuit 87 (engine management) ON.
• Engine running.
• Vehicle rolling.
• Accelerator not actuated.
• Selector lever position "D" or "R".
• Vehicle not in cruise control or DISTRONIC PLUS mode (with code ET4 (DISTRONIC PLUS)).

Deceleration fuel shutoff, general 

The overrun mode fuel shutoff causes the engine to transmit a braking torque to the drive gears via the transmission.

The CDI control unit (N3/31) performs a overrun mode fuel shutoff depending on the following signals:

• Coolant temperature sensor
• Accelerator pedal module, accelerator pedal position
• Crankshaft position sensor, engine speed
• Clutch travel sensor (manual transmission with code MJ8 (ECO start/stop function)) via the drive CAN and powertrain control unit
• Clutch pedal switch (manual transmission without code MJ8 (ECO start/stop function)) via drive CAN and powertrain control unit
• Top clutch pedal switch (manual transmission without code MJ8 (ECO start/stop function)) via the drive CAN and powertrain control unit
• Fully integrated transmission control (VGS) electric controller unit (with code G42 (7G-TRONIC PLUS)), drive range via drive CAN

Deceleration fuel shutoff, function sequence 

If the accelerator pedal is not actuated (zero quantity delivery), deceleration mode is triggered. The CDI control unit switches off the fuel injectors in overrun mode dependent on the coolant temperature, the engaged gear, and at an engine speed of > 600 RPM.

The CDI control unit also lowers the fuel pressure in the rails via the pressure regulating valve. If the accelerator pedal is actuated or the engine speed decreases to < 1,600 RPM, the CDI control unit actuates the fuel injectors again. It also increases the fuel pressure in the rails via the quantity control valve or the pressure regulating valve, depending on the type of regulation.

If the clutch pedal is actuated for vehicles with manual transmission, the overrun mode fuel shutoff is then canceled or suppressed.