2009 Volvo EC 290 CL excavator engine problem

I am facing a problem. When I start my 2009 Volvo EC 290 CL excavator, it does not start until I press the manual fuel pump for the diesel filter, and after the engine rotates for a few 800 revolutions, it gives me a signal, “Engine error turn off engine . and when I turn it off, it only works again. After I pressed the hand pump for the diesel filter, I replaced the diesel return coil and the diesel pressure sensor, and renewed all the nozzles, and the problem still did not go away. A note to those interested: If the engine runs at high revolutions from the beginning, 1300, and I work on 1,500 revolutions, I notice during work that the engine’s revolutions decrease with effort by an amount of 180 to 200 revolutions, and it remains stable without work or effort on the engine, but I cannot reduce the number of revolutions, otherwise I will face the same problem , please all experts,,, help me, thank you