When moving the boom and bucket up looks like engine getting overloaded and trying to stop. What can be the reason please suggest.
Not enough fuel? Check fuel filters and fuel screens for blockage.
First of all thanks for your valuable reply. I will check what you said. But Engine is running normally without any problem even when excavator moving in any direction. Fuel pump, fuel valve and turbo overhauled. But still same problem. Engine starts to gasp/trying to stop when boom started to move up only. Is it possible that during boom up, hydraulic pump getting overloaded due to defective relief valve?
When you make the engine do more work, it needs more fuel and air. If your fuel supply is restricted, then the engine will struggle under load. Or perhaps you have a hydraulic function that is blocking the oil flow? Is it only one function that slows the engine?
Yes during only function (during boom up) engine trying to get slow. During other function engine works normally. Even during boom down from up condition, that time also no problem with engine. It was also observed that if boom up slowly, engine works normal. But if boom up quickly, then only engine starts to get slow.
You might have something going on with your boom hydraulic circuit, but still your Power Shift or TVC or torque limiter ( it has many different names) should not allow engine to overload. We really don’t have Sumitimos here in the US, here they rebranded Case. Is that any way you can find out to which Case model your machine similar to?
SUMITOMO have 2 kinds of SH225X . SH225X-3 with ISUZU BB-6BG1T engine and SH225X-3B with ISUZU AI 4HK1X engine. What type is your machine??