Analysis of Fault Causes 1 Slow and weak excavator movements are commonly caused by a malfunction in the main relief valve.

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2 Modern excavators utilize pilot-operated relief valves; common reasons for their failure include:

① Abnormal pressure settings

② Wear on the poppet valve’s conical surface

③ Clogging of the pilot spool’s damping orifice

④ Broken springs, etc.

3 These are the common causes of this issue. So, what should an operator do when this fault occurs during operation? How can the cause be identified and the problem resolved? Our repair technicians offer the following advice.

4 If this fault occurs, first swap the suspected faulty main relief valve with a known good one and test the machine; if the fault moves to the other circuit, the main relief valve is confirmed as the culprit.

5 If the fault does not move after swapping, further troubleshooting is required. Further reading: Common causes for slow and weak boom movement:

1 Blockage in the hydraulic circuit.

2 Hydraulic leaks (caused by seal failure, improper assembly, loose fittings, seal degradation, etc.).

3 Internal leakage in the boom spool valve or cylinder causing slow/weak boom movement.

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4 Internal leakage in the boom cylinder.

5 Issues with the boom spool valve.