When the excavator suddenly slows down, emits black smoke and fuel consumption increases sharply for a period of time, the maintenance personnel remind that it is necessary to check the fuel injector first. However, in the face of a fault problem, we should be careful in the process of maintenance, and check the fault phenomenon one by one. This article will explain how to judge and troubleshoot according to an example for reference only.
1. Fault phenomenon
A large amount of white smoke is emitted from the lower exhaust pipe of the excavator, and oil drops from the lower exhaust pipe can be obviously observed, about 5-6 drops per minute.
2. Troubleshooting process
1) The maintenance personnel found that the final injection volume of the second cylinder of the machine was 3.5mm3/st, while the final injection volume of the first, third and fourth cylinders was -0.8. Although the data deviation was small, the maintenance personnel thought that the second cylinder was abnormal according to experience.
2) The maintenance personnel passed the second cylinder disconnection test, and the phenomenon was not obvious. Because no specific reason was found at that time, the construction was resumed temporarily. However, the fault phenomenon is obviously aggravated.
3) After re inspection, it was found that the oil seal at the cylinder-2 injectors had been broken and the oil had been sprayed from there. When the valve cover was opened, it was found that the bolts of the cylinder-2 injectors had been loosened and the injector shook back and forth to wear the oil seal.
4) It is found that the front end of the injectors is obviously worn. Due to the looseness of the cylinder-2 injectors, the injected high-pressure diesel can not fully enter the combustion chamber, and some foggy diesel will be injected back into the valve cover. A certain pressure is formed in the valve cover, so that the oil will be discharged along the lower exhaust pipe, accompanied by some white smoke.
3. Troubleshooting
Replace the injectors and oil seal of the second cylinder, tighten the pressure block bolts of the injectors, and replace the engine oil and filter. After that, the white smoke and dripping of engine oil in the test run are eliminated and the operation is normal.
4. Check the injection status of fuel injector
Some fuel injector injection status checks are summarized, which can be compared and referenced to find faults in time.
1) injectors should not be able to see large grains of spray when the fuel injectors is sprayed, and there should be no intermittent spray.
2) In the initial injection stage of the fuel injectors, the injected particles should be fine, the injection is intermittent, and there should be no oil droplets.
3) The angle of spray distribution must be normal.
5. Adjustment mode of fuel injector
Loosen the lock nut and adjust the adjusting screw to adjust the injection pressure. Rotate clockwise to increase the pressure and counterclockwise to reduce the pressure. After adjustment, tighten the lock nut again.
