Diesel quality issues leading to excavator malfunction case two

A certain customer has two unitsKobelco excavatorWorking on the same construction site and on the same day, there is a slow movement of the entire vehicle (both compound and individual movements are relatively slow), and the walking and rotation are not very obvious, and there is no deviation phenomenon. No alarm display. The engine is easy to start, the smoke color is normal, and there is no abnormal noise. According to the feedback from the operator, the speed is gradually decreasing.

Testing process:

1. After checking the after-sales diagnosis, abnormal data was found for item NO9: During operation, E-1 \ E-2 detected a reduction in engine power of 25mA (normal is 0MA) and a hydraulic oil flow rate of 45L (normal is 80-95L). Based on this, it is estimated that the engine power is insufficient. The adjustment of mechanical and electrical components A, B, and C can be completed smoothly. The test drive malfunction persists.
2. The intake system (turbocharger, intercooler, pipeline, filter element) shows no abnormal phenomena, the oil system shows no air leakage, and the filter element is dirty. After replacing with a new one, the fault still persists during the test drive.
3. The pilot pressure can reach 50 kilograms (the pilot filter element is not clogged), and the low-pressure sensor can monitor 30 kilograms of pilot pressure
4. When the boom rises and overflows, the engine speed is adjusted to about 50 revolutions per minute and then rises to the normal speed of 2150 revolutions per minute. At low idle, the boom rises and the overflow engine speed drops to around 500 revolutions per minute.
5. No abnormal sensor or solenoid valve data was observed during individual and composite actions.
6. Check that the return oil filter element is clean and not clogged.
7. The high-pressure sensor and solenoid valve on the pump are still malfunctioning.
8. Create performance and cylinder compensation curves for the engine. After analysis, it was found that the suction pressure was low (170kpa) and the injection volume was large at 130mm3/stcyl, while other curves were basically normal. The compensation value for cylinder 1 is 0.4, the compensation value for cylinder 2 is 0, the compensation value for cylinder 3 is 0.4, and the compensation value for cylinder 4 is 0.4.

Solution:

Preliminary assumption: Due to the same fault phenomenon at the same construction site, the most likely hardware failure is caused by the quality of diesel oil.
1. The fault persists even after replacing the SCV solenoid valve.
2. After contacting the company's technical department, it has been decided to replace a set of injectors. After the replacement, the QR code and learning value were corrected, and the test action and engine performance were restored to normal.

Repair conclusion:

1. If the cylinder compensation value is within ± 8, the fuel injector may not be normal.
2. According to the performance curve, it is found that when the injection volume increases compared to the standard value and the suction pressure is low, the injector may be damaged.
3. Require customers to perform daily maintenance and use oil-based diesel. Otherwise, the consequences will be borne by the customer, and the diesel is contracted by the local contractor, so the oil quality is poor. The customer is required to replace the front and rear diesel filters within 250 hours.