Fuel Pressure Regulating - DECOS

Fuel Pressure Regulating - DECOS

The fuel pressure regulating for demand controlled fuel pump (DECOS - DEmand COntrolled fuel Supply), means that the fuel pressure is infinitely variable by vary the power of the fuel pump. The systems construction implies among other things that a larger maximum pressure (approx. 5.5 bar) is allowed in the fuel pump. This pressure is used in extreme situations, for instance at high engine load. Following components are used for fuel pressure regulating:
- Engine Control Module (ECM)
- Fuel pump control module
- Fuel pressure sensor with Fuel temperature sensor
- Fuel pump

The time for start process of the engine can be decreased by quickly raising the pressure in the fuel distribution pipe, when ECM receive a signal from Central Electronic Module (CEM) about position of the ignition switch. ECM can easier calculate the injection time for the injection valves, because the signal from the fuel pressure sensor provides information about current fuel pressure. Especially cold start properties of the engine are improved. Advantages which receives when not all power of the fuel pump is used continuously are:
- The total current consumption of the fuel pump decreased which bring about the power-supply system being discharged.
- The fuel pump durability will increase.
- Noise from the fuel pump is decreased.

The Engine Control Module (ECM) calculates which fuel pressure that shall be reached. After that a signal will be sent to the Fuel pump control module with a request for desired fuel pressure. This is performed via serial communication between ECM and the Fuel pump control module. By changing the PWM-signal the fuel pump can be infinitely variable. Only the needed pressure will be delivered to the Fuel distribution pipe/Injection valves. The value of the PWM-signal is a measure on workload of the Fuel pump (% duty, 100% = maximum pressure).

The ECM is continually monitoring the fuel pressure by means of a signal from the Fuel pressure sensor. Thereby, desired fuel pressure can be reached and on condition a signal will be sent to the Fuel pump control module with a request to adjusting the fuel pressure.

If the control module in Supplemental Restraint System (SRS) detects a collision the Engine Control Module, by reasons of security, will cut off the fuel pump.