Resolved slow moving issue on Caterpillar 320D Hydraulic Excavator

Here is a real case of my friend. His Caterpillar 320D is very difficult to operate and moves slowly. Even with no load, it takes more than 10+ seconds to turn around. How he solved this puzzle, read here!

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Before Repairing,here ask some question for the problem:
Question 1:Does your Caterpillar 320D engine rotate speed correctly during full load.
Answer 1:Yes,the engine rotate speed is correct,when it with full load.
Question 2:Is the engine smog color looked correctly when it will full load?
Answer 2:Yes,it is heath

Caterpillar 320D Move Slowly Diagnostics:

1.Caterpillar 320D excavator can work with 3 modes:Elaborate mode,common mode and heavy load mode.The 3 work modes work related load:75%,90% and 100%.If the CAT 320D is set under elaborate mode,maybe cause move slowly.(Customer check it work on heavy load mode)

2.Because the engine rotate speed and engine smog are correctly,so the engine is work fine.It maybe the hydraulic system get trouble.

1) Pilot system control oil line with low pressure
The pilot pump provides pressure oil for the pilot system called main control oil line,it can make excavator do related motion.If the pilot system fails and the pilot system pressure is too low,it will cause pilot oil can not control the main control valve or the main control valve spool travel will be shortly,so it will make excavator move slowly.
2) Main pump with low pressure
3) Hydraulic oil line is blocked or hydraulic filter air-logged.

Caterpillar 320D Move Slowly Repair:

1.Check hydraulic oil,it is normal
2.Measure the pressure of the reducing valve is 10kg/cm2,and the inner filter was blocked
3.The hydraulic oil tank was duty and there is a lot of impurities.
4.Pilot pump work fine


Clean the hydraulic system 3 time and replace the hydraulic oil and filter.

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