Method and device for operation of a high pressure fuel pump

In a system for fuel injection in a combustion engine, a device for controlling functionality, wherein the system comprises:

• a feeding pump, controllable independently of the combustion engine, and configured for supplying fuel in a low pressure part of the system to the high pressure pump, an accumulator tank for fuel injection to the combustion engine, the high pressure pump comprises at least one pump element which is connected between the low pressure part and the accumulator tank, the pump element has one cylinder including a pump chamber with a moveable piston therein for pumping;
• the cylinder having a connecting opening to the low pressure part;
• an inlet valve arranged in the cylinder's connecting opening, the inlet valve being controllable to control a flow of fuel into the pump chamber;
• first measuring elements configured to measure a first fuel pressure (Pin) in a position in the low pressure part and at the inlet to the high pressure pump, second measuring elements configured to measure a second fuel pressure (PS) in the accumulator tank;
• a control device configured to control the feeding pump during stationary operating modes of the combustion engine with a constant requested reference value (PB) for the fuel pressure in the accumulator tank, the control device is configured to control the feeding pump to reduce the first fuel pressure
• Pin in the position in the low pressure part, the first and second measuring elements being configured to measure the first fuel pressure (Pin) in the low pressure part and the second fuel pressure (PS) in the accumulator tank during pressure reduction in the low pressure part;
• and
• a device configured to compare development of the accumulator tank second pressure (PS) with a reference value (PB) during the pressure reduction in the low pressure part, via control of the feeding pump and based on the comparison, the device generates information about the high pressure pump's functionality.