Rail Pressure Control DDE 4.0

The following components belong to the common rail system and influence the rail pressure control:

• High pressure pump (HDP)
  
• Rail pressure control valve
  
• Rail pressure sensor
  
• High pressure lines
  
• Fuel injectors
  

Rail pressure monitoring

The rail pressure is monitored during engine start and engine operation by way of setpoint/actual value comparison. The rail pressure sensor supplies the actual value to the DDE. The setpoint is calculated by the DDE depending on the operating status. Fault code 1190 ”Rail pressure control” is stored if the DDE determines an impermissible deviation in the rail pressure from the setpoint.

An impermissible deviation of the rail pressure from the setpoint can be caused by the following:

• External leaks at components in the common rail system
  
• Internal leaks in common rail system, e.g.
  
  • In the high pressure pump (e.g. worn piston)
    
  • At the rail pressure control valve (too little or too much volume in the return flow)
    
  • At the fuel injectors (too much volume in the return flow)
    
• External influences such as defective fuel supply, clogged fuel return system, air in fuel system
  

As from DDE software version B1 (phase-in as from 07/2000), the DDE warning lamp will be activated if fault 1190 occurs. In addition, fault code 1612 ”DDE warning lamp activated” will be stored. This fault code only indicates that the DDE warning lamp has been activated due to a fault in the rail pressure control system.

Troubleshooting

Engine start will not be possible or the engine shuts down if the DDE recognizes an impermissible rail pressure deviation.