What are the Precautions for the Assembly Process of the Excavator Fuel Injection Pump

by MOU YONG HONG on December 02, 2021

The assembly quality of the fuel injection pump plays a decisive role in checking and adjusting. The faults and rework caused during the verification are mostly caused by poor assembly quality. Therefore, the assembly process should be conscientious and meticulous, and it should be checked repeatedly.

1. Special tools for disassembly

Before disassembling and assembling, we must clean and prepare the required tools, especially the special tools. During the disassembly and assembly process, open-end wrenches, Torx wrenches, socket wrenches, and various special tools must be used. Universal tools such as adjustable wrenches are not necessary. Especially for tight-fitting parts, special tools should be used as much as possible, and tools that easily damage parts such as hammers and chisels should not be used.

2. Precautions and points for disassembly

2-1. The disassembled parts should be arranged in order according to the parts so that they can be matched with each other during installation.

2-2. The fuel injection pump should be disassembled on a special fixture to avoid the deformation of the casing. If it is disassembled on the vise, it is necessary to install copper plates and other software on the jaw to avoid damage to the parts. The clamping part must not be on the mating surface or the mounting surface.

2-3. Keep the parts, tools, and workbench tidy at all times.

2-4. Plungers and plunger sleeves, oil outlet valves and valve seats and other precision couples should be very careful during disassembly, cleaning, and storage, and should not collide with each other, nor can they be exchanged with each other. In diesel.

2-5. Before disassembling the fuel injection pump, the surface should be cleaned with gasoline, kerosene or diesel oil, and care should be taken not to use alkaline water for cleaning.

2-6. Some parts that require the same assembly position, such as gear bar, manipulator's arm, and adjustment screw, should be memorized with the original assembly position by marking when disassembling, in order to facilitate correct assembly.

3. Precautions and points for assembly

3-1. The whole assembly process must be kept highly clean. There should be no dust or smoke in the surrounding air. Workbenches, parts, tools, and assembler's hands must be clean.

3-2. During assembly, various seals, O-rings, oil seals, etc. are replaced with new ones.

3-3. Strictly follow the assembly process sequence and technical standards, and use the instruments and measuring tools to check item by item. The order of assembly should generally be carried out in the reverse step of disassembly, and many precautions are the same as those of disassembly.

4. The basic operation points of assembly

4-1. The plunger and plunger sleeve are matched together and cannot be replaced. Before installing the fuel injection pump body, you should check whether their model matches the fuel injection pump installed. The plunger sleeves with the same height adjustment of the roller transmission components can have different plunger diameters. If the plunger diameters are incorrectly installed, it is impossible to achieve normal oil supply. The plungers of the same diameter are installed on the left or right side of the diesel engine according to the fuel injection pump, and are divided into "left engine" and "right engine". The chute of the plunger head is also divided into "left-handed" and "right-handed", corresponding to "left machine" and "right machine". If it is installed incorrectly, it will cause the joystick to move in the direction of increasing fuel supply, but the plunger will move in the direction of reducing fuel supply. Such a fuel injection pump will not work. When replacing with a new plunger and plunger sleeve, it can be used with The original old parts are compared with each other to avoid mistakes.

4-2. When installing the oil outlet valve and valve seat, pay attention to the cleanliness of the upper-end surface of the plunger sleeve and the lower end surface of the oil outlet valve seat to make the joint surface tight. If mechanical impurities are trapped, the plunger will leak high-pressure oil during operation, making the uniformity of the oil supply of each cylinder impossible to adjust. There should be a slight gap between the inner diameter of the outlet valve gasket and the outer diameter of the outlet valve body. If it is too tight after the oil outlet valve seat is pressed tightly, the oil outlet valve seat will be deformed, and there is a risk of the oil outlet valve being stuck. The outer diameter of the gasket cannot be too small, otherwise, the seal is not tight, and low-pressure oil will leak from the gap of the screw hole of the oil valve compression seat on the pump body. When screwing in the oil outlet valve to tighten the seat, the torque of 49~68. SN.m is suitable. Overtightening will deform the plunger sleeve, and the plunger will become stuck in the plunger sleeve. When there is no torque wrench or lack of experience, tighten the oil valve compression seat, and you can install the plunger into the plunger sleeve for testing if the plunger moves freely. If it feels awkward, it means that the torque is too large, and you can slowly loosen the oil valve to tighten the seat until it is suitable.

4-3. When installing the plunger, it should be careful and accurate, and should not touch the hair or install it wrong. After loading, it should be able to move up, down, left, and right freely. On the fuel injection pump of the rack-type control mechanism, both directions of the lower end of the plunger can be installed into the straight cut groove of the control sleeve. Generally, the manufacturer has marked the tongue on the lower end of the plunger. The mark should face upwards.

4-4. When the hole on the pump body is deformed or has burrs, and the plunger set does not enter, the reamer should be used to ream the hole so that the plunger set can be installed loosely.

4-5. When installing the camshaft, the rotation direction and injection sequence of the fuel injection pump should be clarified before being installed in the pump body. The oil seals at both ends should seal the lubricating oil inside the pump body and cannot be installed incorrectly. After the bearing seats on both sides are installed, the rotation of the camshaft should be flexible, and the axial clearance should meet the requirements of the specifications.

4-6. After being repaired and installed, the roller transmission parts should be moved up and down flexibly when turning the L-J Dust Torx L camshaft after being installed in the pump body, and no stagnation is allowed. The adjustment screw on it should be adjusted in advance, not too high, otherwise, the plunger and other parts will be crushed during the subsequent assembly and tightening process.

4-7. When installing the plunger spring, the upper and lower plunger spring seats must not be reversed, otherwise, the fuel injection pump will be partially stuck. When installing the spring upper seat, check whether the adjusting ring gear has axial clearance. If the adjusting ring gear is dead, it means that the spring seat hole is worn, and the corresponding spring upper seat should be re-configured or a circular ring pad should be added on the spring upper seat to ensure the flexible rotation of the adjusting ring gear. The wire retaining ring of the lower spring seat should be installed into the groove, and no skew phenomenon is allowed.

4-8. Before the adjustment gear ring is installed, the adjustment gear rod should be installed into the pump body and the installation position should be determined. When there are engraved marks on the adjustment gear bar, the engraved lines should be directly opposite the end face of the pump casing. When there is a punching mark on the adjusting gear bar, the punching eye and the adjusting gear bar bush on the pump body should be aligned. Then keep the position of the adjusting gear bar unchanged, install the adjusting gear ring, and make it mesh with the adjusting gear bar. The opening side of the adjusting ring gear should be facing outwards. At this time, the matching position of the adjusting ring gear and the control sleeve can be temporarily ignored. After the pump body is installed, loosen the locking screw on the adjusting ring gear and align the marks (When the fuel injection pump leaves the factory, adjust the joint between the ring gear and the control sleeve, make a hard mark with a chisel, or mark painted with paint) and tighten. For fuel injection pumps that do not have a gear rod assembly mark or whose gear ring opening is not upward, the assembly should be strictly in accordance with the marks made during disassembly, otherwise, it will cause great difficulty in debugging and even cause all rework. When the fuel injection pump has been assembled, if the meshing position of the adjusting gear ring and the adjusting gear rod is found to be incorrect, there is no need to disassemble it again. You can pry the adjusting gear ring together with the control sleeve with a screwdriver to make them and the adjusting gear The rods are disengaged, then turn the ring gear or move the rods, and then loosen the screwdriver to get them in the correct meshing position.


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