Fuel injection pump

The utility model discloses a fuel injection pump, and belongs to the high-pressure common rail technology. The plunger pump comprises a pump body and a plunger assembly, the plunger assembly comprises a plunger sleeve, a stud and a nut, the stud comprises a first threaded section and a second threaded section, the first threaded section is connected with the pump body, and the second threaded section extends out of the pump body and is connected with the nut. The fixing part of the plunger sleeve is located on the outer side of the pump body, arranged on the stud in a sleeving mode and pressed and fixed to the surface of the pump body through the nut. The nut is provided with a pre-tightening position and a working position relative to the stud, in the pre-tightening position state, the nut is loaded with first pre-tightening torque, the nut is tightened by a first angle on the basis of the pre-tightening position to reach the working position, and when the fuel oil injection pump works, the nut is located a