The reason for the poor rotation of the gear pump:

① Axial clearance or radial clearance is too small. Re-adjust the repair.

② There are dirt in the pump. Disintegrate to remove foreign matter. 

③ Assembly is wrong. The machining datum of the pin hole of the gear pump is not fitted with the datum plane. If the pin is driven first, then the screw is tightened and the pump will not turn. The correct way is to turn the gear pump while tightening the screw, and finally with a drill hole and into the pin. 

④ Pump and engine coupling coaxial difference. Coaxiality should be guaranteed within 0.1mm. 

⑤ Pump parts are not demagnetized. All parts must be demagnetized before assembly. 

⑥ Needle roller sleeve quality failure or needle roller break. Repair or replace.

⑦ The oil output port is blocked. Clear foreign matter.