Made in China Fuel Injection Pump Plunger 2 418 455 407 2455-407 Pump Elements Engine Accessories

Appearance inspection
Observe the plunger surface directly to check whether there are obvious scratches, abrasions, wear grooves or discoloration. Focus on checking the cylindrical surface where the plunger and the plunger sleeve fit and the part where the head contacts the oil outlet valve. If there are obvious signs of wear on the plunger surface, such as bright wear bands and deep scratches, it means that the plunger may have been severely worn.

Measure the size
Use precision measuring tools, such as micrometers and calipers, to measure the key dimensions of the plunger, including the diameter of the cylindrical part, the size of the head, etc., and compare them with the original design dimensions or the standard dimensions in the maintenance manual. Since wear will cause the plunger size to become smaller, if the deviation between the measured value and the standard value exceeds the allowable tolerance range, it usually indicates that the plunger is worn. Generally speaking, the allowable range of wear of the plunger diameter is between a few microns and tens of microns, which varies from vehicle model to vehicle model and oil pump model.

Check the fit clearance
The fit clearance between the plunger and the plunger sleeve can be checked using a special gauge or by calculation. A simple method is to put the plunger into the plunger sleeve, and then gently shake the plunger in the vertical direction to observe whether the gap between the plunger and the plunger sleeve is too large. If you feel obvious shaking or abnormal gap, it may be that the gap is increased due to wear. You can also calculate the fit clearance by measuring the inner and outer diameters of the plunger and the plunger sleeve, and compare it with the standard clearance value. The normal fit clearance is usually between a few microns and more than ten microns. If the actual clearance exceeds the standard range, it indicates that the plunger and the plunger sleeve may be worn.

Pressure test
Use a fuel pressure gauge to connect to the fuel system and measure the pressure of the fuel system when the engine is running or the oil pump is working. If the oil pump plunger is worn, it will cause increased fuel leakage, thereby reducing the pressure of the fuel system. Compare the measured pressure value with the standard pressure value specified in the vehicle maintenance manual. If the actual pressure is significantly lower than the standard value, and other factors that may cause the pressure drop (such as fuel filter blockage, oil outlet valve failure, etc.) are excluded, it is likely caused by wear of the oil pump plunger.

Observe the engine running status
When the oil pump plunger is worn, it will affect the supply and injection of fuel, which will cause some abnormal phenomena in the engine. For example, the engine may have difficulty starting, insufficient power, slow acceleration, unstable operation, increased vibration, etc., and may also be accompanied by black smoke from the exhaust pipe and increased fuel consumption. If the engine has these phenomena and other components have been checked and ruled out, it is necessary to consider whether the oil pump plunger is worn.

Oil pump test bench inspection
Remove the oil pump from the engine and install it on the oil pump test bench for comprehensive inspection. The test bench can simulate various working conditions of the engine and accurately test the performance of the oil pump. On the test bench, the oil pump's oil supply, oil supply pressure, injection timing and other parameters at different speeds and loads can be measured and compared with standard values. If problems such as insufficient oil supply, unstable pressure or inaccurate injection timing are found, and the influence of other components is ruled out, then the oil pump plunger is likely to be worn.