Wear characteristics, identification and repair of plunger oil pumps

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Wear characteristics, identification and repair of plunger oil pumps 1. Wear characteristics, identification and repair of plunger and coupling parts 1. Wear characteristics of plunger and coupling parts The wear of plunger coupling parts is mainly concentrated on the plunger head, lintel, stop supply side and the oil inlet and return hole of the plunger. (1) The wear characteristics of the plunger head are the largest. There are groove marks that are deep at the top and shallow at the bottom, thick at the top and thin at the bottom on the contact surface. The worn area is milky white, which is especially obvious under light. The maximum depth of the groove mark can reach 0.023-0.025 mm, the maximum width is 4-5 mm, and the length is about 10 mm. (2. Wear characteristics of the plunger head lintel. The wear here is smaller than that of the plunger head. Most of them are comb-shaped and not deep fine grooves. They are also deep at the top and shallow at the bottom, thick at the top and thin at the bottom. (3) The wear characteristics of the stop and supply edge of the plunger gradually decrease from the upper edge of the chute upward. The wear width is about 5 mm and is milky white. At the same time, the edge of the stop and supply edge is blunted and rounded. (4) Wear characteristics of the lower shoulder of the plunger. The wear here is very small, with only short fine lines on the shoulder circumference. (5) Wear characteristics of the plunger sleeve The wear is mainly near the oil inlet and return holes, and the oil inlet hole is larger than the oil return hole. The wear part of the oil inlet hole is near the center line of the hole. The upper wear extends upward from the upper edge of the hole by about 6-7 mm and is about 0.024-0.027 mm deep. The lower wear extends downward from the lower edge of the hole by about 4.5 mm and is about 0.015-0.017 mm deep. The wear width is approximately larger than the hole diameter. The surface wear near the oil return hole is mainly on the left side, about 2-2.5 mm wide, extending upward by 2-3 mm, and downward by 4-5 mm. The wear on the right side of the hole is very small. 2. Identification of plunger parts For the identification of plunger parts, first conduct a general visual inspection to see if there are any obvious defects. For those that are qualified or cannot be determined, further identification is carried out through testing. (1) Visual inspection: Use the naked eye to see that the head of the plunger, around the stop edge or around the oil hole of the plunger sleeve are milky white due to wear, and there is a clear feeling when scratched with a fingernail. The plunger or sleeve has rust and cracks, and there is peeling on the top of the plunger or the stop edge. If there is any of the above defects, the plunger assembly will be scrapped. (2) Use the simple vacuum method to identify the top hole of the plunger with your right index finger, and slowly pull the plunger out with your left hand. At this time, your right index finger should feel suction. When it is pulled to about 2/5 of the total length of the plunger, quickly release the plunger. At this time, the plunger will quickly return to its original position under the action of vacuum suction. ； Indicates that this plunger can continue to be used. Otherwise, it should be replaced with new parts or repaired. (3) The sealing test can be tested with an injector tester. Install the plunger couple into the fuel injection pump body, install the oil delivery valve seat and other parts. Do not install the oil delivery valve and oil delivery valve spring. Tighten the oil delivery valve tight seat, and connect the oil delivery valve tight seat end of the fuel injection pump to the injector. Put the plunger at the maximum oil supply position at the high-pressure oil pipe joint of the injector tester, press the hand lever of the injector tester to raise the oil pressure to 22540 kPa, stop pumping oil, and measure the time required for the oil pressure to drop from 19600 kPa to 9800 kPa. Its value should be between 16-29 seconds. Otherwise, it is considered unqualified. 3. Repair of the plunger couple (1) If the upper end face of the plunger sleeve is uneven, you can use abrasive paste with a particle size of more than 600 to apply it on the thick glass and grind the upper end face. When grinding, the plunger sleeve should be kept perpendicular to the glass plate, the force should be light and even, while turning and moving, and constantly changing the direction of rotation, until the end surface is smooth and without scratches. (2) Blockage of the plunger in the plunger sleeve is generally common in newly replaced plunger pairs. You can apply engine oil to the plunger guide part and grind it with the plunger sleeve. If the tightness is too great, polishing paste should be applied and rubbed together. When grinding, you can use a bench drill or hand drill to clamp the plunger, and use your right hand to hold the plunger sleeve and move it back and forth to grind it. For the plunger with burrs on the top, you can use a fine oil stone with a grain size of 800, apply engine oil, tilt the plunger about 30 degrees, and gently turn the plunger to remove the burrs. (3) For severely worn plunger parts, new parts should be replaced. 2. Wear characteristics, identification and repair of oil delivery valve parts 1. Wear characteristics of oil delivery valve parts The wear of oil delivery valve parts is mainly on the sealing cone surface, pressure reducing ring belt and guide part. (1) Wear characteristics of the sealing cone surface The wear is greater here, which increases the width of the valve seat sealing ring and reduces the smoothness ； An annular groove appears on the cone surface of the oil delivery valve, with a depth of approximately 0.05 mm. (2) The wear characteristics of the decompression annular belt are also relatively large here. After wear, the decompression annular belt is tapered, larger at the top and smaller at the bottom. ； The surface of the cylinder is covered with grooves, shallow at the top and deep at the bottom. ； The lower edge of the decompression ring is rounded due to wear. (3) Wear characteristics of the guide surface. The wear here is small. After wear, the upper part is larger than the lower part. There is also wear on the guide part where the oil outlet valve seat and the oil outlet valve seat decompression ring match. 2. Identification of oil delivery valve parts (1) Generally, the identification is done by visual inspection. If the oil delivery valve parts have one of the following defects, they can no longer be used. ①The decompression ring has serious signs of wear, with milky white axial scratches that can be clearly felt when scratched with a fingernail, or the axial scratches on the circumference of the decompression ring are so dense that the original surface finish cannot be seen. ②The sealing cone surface is too worn, the sealing ring is too wide or there is collapse in the sealing ring. ③When the oil delivery valve and valve seat are corroded, or have metal peeling or deep abrasive scratches. ④When the lower plane of the oil outlet valve seat is severely corroded. ⑤There are obvious annular groove marks on the sealing cone surface of the oil outlet valve seat, which can be felt when scratched with a fingernail. (2) Simple test and identification of the sealing performance of the oil delivery valve assembly ① Simple test and identification of the sealing cone surface Hold the oil delivery valve seat with your thumb and middle finger, press the oil delivery valve against the valve seat with your index finger, suck out the hole on the lower plane of the oil valve seat with your mouth, and move it to your lips. If it can be sucked by the lips, it means the sealing performance is good. You can also install the oil outlet valve assembly into the oil pump body without installing the plunger, and pass 294-490 kPa compressed air from the high-pressure oil pipe joint for inspection. If there is no air leakage, the sealing performance is good, otherwise it should be repaired or replaced with new parts. ②Simple sealing performance test identification of the decompression ring: Use your thumb to press the hole on the lower plane of the oil delivery valve seat, place the oil delivery valve into the valve seat, and gently press down with your index finger. When the decompression ring enters the valve seat, you will feel the upward rebound force of the compressed air. When the index finger is released, the oil outlet valve can rebound up, then it is said. It is clear that the sealing between the pressure reducing ring and the oil outlet valve seat hole is good, otherwise it is unqualified. For newly replaced oil delivery valve parts, a sliding test must also be carried out. Take out the oil delivery valve assembly that has been soaked in diesel oil, hold the valve seat, and keep it in a vertical position. Then pull out the oil delivery valve by about 1/3 of the curve of the valve body, that is, let go. The valve body should be able to fall to the valve seat under its own weight. Then rotate the oil delivery valve at any angle and test. The results should be the same. 3. Repair of oil delivery valve parts The key part that determines whether the oil delivery valve can continue to work is the sealing cone surface. When the sealing cone surface is slightly worn or has poor contact, you can evenly apply abrasive paste on the sealing cone surface, then insert it into the valve seat and rotate it for grinding. After grinding several times, switch to another direction for grinding. Be careful not to let the abrasive paste stick to the pressure relief ring. After grinding for a certain period of time, clean off the grinding paste, then dip it in diesel oil and grind it with each other, and tap the oil outlet valve on the valve seat several times. Grind, clean, and then conduct sealing performance test.