1. Pilot control oil circuit diagram and cut-off part table during measurement
The pilot control oil circuit is shown in Figure 1-3. The cut-off parts during measurement are shown in Table 1-15.
2. Trouble diagnosis and troubleshooting steps
(1) First check whether the overflow pressure of the pilot pump is normal (the engine is running at high speed without load, the overflow pressure is 3.281MPa), if the measured value is lower than the specified value, refer to Figure 1-3 and follow the table 1-15 The indicated cut-off location measures the overflow pressure step by step. If the overflow pressure is within the specified range, it means that the internal leakage of the truncated component is too large and should be repaired or replaced; if the overflow pressure is still lower than the specified value, check the pilot pump outlet filter screen for foreign objects.
(2) If there is foreign matter in the oil outlet filter of the pilot pump, it means that the pilot pump is faulty; if there is no foreign body, it means that the pilot pump overflow valve is faulty, and the fault can be eliminated after replacement.
(3) If the overflow pressure of the pilot pump is in the range of 3.2 & 1MPa at the beginning of the inspection, check whether the overflow pressure of the front and rear hydraulic pumps is normal (in the mode of H, the working mode is HO, and the engine is measured at no-load high-speed operation , During normal overflow, the overflow pressure is 31 ~ 34MPa; during the secondary overflow, the overflow pressure is 32.5 ~ 36.5MPa).
(4) If the relief pressure of the front and rear hydraulic pumps is lower than the standard value, adjust the main relief valve, and then measure the relief pressure of the front and rear hydraulic pumps after adjustment. If the overflow pressure returns to normal, it indicates that the fault has been eliminated; if the overflow pressure has not reached the standard value, it indicates that the main overflow valve is faulty. After repair or replacement, the fault can be eliminated.
(5) If the overflow pressure of the front and rear hydraulic pumps is in the range of 31 ~ 34MPa, continue to check whether the set pressure of the TVC valve (torsion control valve) is normal (working mode is H.0, mode is H, engine No-load high-speed operation, No. 1 hydraulic pump overflows, the set pressure is (1.4 ± 0.1) MPa).
(6) If the set pressure of the TVC valve is not within the specified range, adjust the IVC valve. If the adjustment returns to normal, the fault is eliminated; if the adjustment does not return to normal, it means that the TVC valve is faulty. After repair or replacement, the fault is eliminated.
(7) If the set pressure of the TVC valve is within the specified range, observe whether the engine speed is normal when the hydraulic pump overflows with the cancellation of the CO valve (working mode is HO, mode is H, and the engine runs at high speed without load, The stick overflows, the CO valve is cancelled, and the engine speed is (2050 ± 60) r / min).
(8) If the hydraulic pump overflows with the cancellation of the CO valve and the engine speed is within the specified range, the cause of the failure is that the internal leakage of the hydraulic pump is too large. After repair or replacement of the new pump, the failure can be eliminated; if the engine speed If it is not within the specified range, it may be explained that the engine fuel system is faulty, and the relevant excavator should be repaired.
