1. Pump axial clearance and radial clearance is too small: axial, radial clearance is too small, you should replace the parts, adjust the axial or radial clearance.
2 needle rotation is not flexible: replace the needle roller bearings.
3. The concentricity of the cover and the shaft is not good: replace the cover so that it is concentric with the shaft.
4. Pressure valve failure: check the pressure valve spring is malfunctioning, the valve hole is blocked by dirt, slide valve and valve body failure; replace the spring, clear the valve hole dirt or change the valve.
5. Coupling pump and motor concentricity is not enough: Adjust the pump shaft and motor coupling concentricity, so that the error does not exceed 0.20mm.
6. Pump impurities: may be left in the assembly of iron, or oil inhalation of impurities; with a thin copper mesh filter system of total loss of oil to remove dirt.