How to deal with the phenomenon of the plunger of the diesel engine fuel injection pump getting stuck
Jamming of the diesel engine fuel injection pump plunger is a common fault. It may be caused by reasons such as the plunger being bent, impurities entering, the positioning screw being too long, the pump body base being uneven, or the new plunger pair being stored for too long. The following are the specific handling methods

Plunger bending
The reason is that the plunger pair was not handled with care during transportation, storage and assembly, causing the plunger to bend slightly.
Handling: The plunger should be replaced in a timely manner to prevent the work from combing or getting stuck due to bending.
Impurities enter the plunger pair
Reason: The plunger was not cleaned thoroughly during assembly, or impurities entered between the plunger pairs. Due to carelessness during assembly, the plunger was scratched and damaged.
Processing
When assembling, install it carefully to avoid damaging the plunger.
Thoroughly clean the plunger pair to prevent impurities from entering between the plunger pairs.
If the plunger has been scratched and damaged, for minor scratches, it can be washed and ground with cleaning engine oil. If the strain is severe, the plunger needs to be replaced.
The sleeve positioning screw is too long
The reason is that if the set screw of the plunger sleeve is too long or the washer is forgotten when installing the set screw, the sleeve will be crushed, causing it to shift.
Processing
If the set screw is too long, it can be appropriately shortened.
When installing the set screws, don't forget to install the washers.
The base of the pump body is uneven
The reason is that the base for installing the pump body plunger sleeve shoulder is uneven or dirty, which affects the assembly accuracy of the sleeve and causes the oil pump plunger to be skewed during assembly.
Processing
Inspection method: Pull the fuel injection pump off the pump body, connect the low-pressure fuel line and turn on the fuel tank switch. Fill the pump body with diesel and wipe the outside of the pump body. If oil leakage is found at the roller, it indicates that the base of the pump body is not level.
Repair method: An old plunger sleeve can be used. Apply a frosted coating on the shoulder, insert it into the pump body, and continuously rotate and gently tap the sleeve for cleaning. After grinding it flat, reassemble it and check for any oil leakage.
The new plunger pair has been stored for too long
The reason is that the new plunger pair has been stored for too long, which can easily lead to oil loss and oxidation reactions, causing the plunger to rust.
Processing
Soak the plunger pair in kerosene or diesel for a period of time.
Then rotate and repeatedly pull the plungers to wear them in with each other until the plunger pair rotates smoothly.
It can be assembled and used only after careful cleaning.
Other situations and their handling
The top edge of the plunger is dented and burrs are produced:
Phenomenon: It is difficult to observe with the naked eye. When the top of the plunger retract into the plunger sleeve, it will feel rough and jammed.
Handling: Do not repeatedly rotate or pull the plunger to avoid burrs scratching the plunger sleeve. The top edge of the plunger should be pulled to be level with the center of the oil inlet hole of the plunger sleeve. Then, slowly rotate the plunger. When the obstruction sensation disappears at a certain position, it indicates that the impact part of the top edge of the plunger is exactly at the oil inlet hole of the plunger sleeve. Mark the position accurately, push the top edge of the plunger out of the plunger sleeve, and use a fine sandpaper to grind the dented area. When grinding, the plane of the fine sand strip should be at a 45° Angle to the axis of the plunger. Gently push and pull it a few times to eliminate the burrs at the edges and corners. However, do not grind too much to avoid affecting the consistency of the starting Angle of fuel supply for each cylinder and the uniformity of the fuel supply volume.
Stuck new fuel injection pump
Processing
Inject an appropriate amount of gasoline or diesel into the fuel injection pump and the governor. Repeatedly rotate the camshaft to ensure that components such as the fuel injection pump twill and the governor fly ball move freely, preventing rust and jamming, which could cause the diesel engine to stall.
For fuel injection pumps with disassemblable upper and lower parts (such as Type I, II, and III fuel injection pumps used in models like 485, 695, 4125, and 6130), place the pump body flat, open the side cover plate, remove the pump head fastening nut, take off the pump head, and use a hand clamp to hold the root of the plunger. Slowly pull out the faulty cylinder plunger and spring (be careful not to damage the plunger) Clean repeatedly with clean gasoline or diesel. After cleaning, reinstall it (note that the plunger adjustment arm must be inserted into the adjustment fork), and alternately tighten the pump head nut. Rotate the camshaft and turn the oil pump control handle to recheck. After the plunger moves back and forth freely and the two racks move forward and backward sensitively, drain the cleaning oil and inject an appropriate amount of clean lubricating oil into the governor housing.