Any ideas
I think we need more information than "getting weak" including serial number Mark
When you say "getting weak" you talking about the engine or hydraulic system? Keep in mind, on most excavators the pump control system will back off the hydraulic performance if the engine is not making power. Checking the engine power can often lead back to the fuel filters or air filter being plugged. Do you know how to get in the monitor panel to retrieve codes? This could be helpful. Like Mark250 asked... What is the serial number??? Gotta have it
Is this the serial# cat0312clcba02080
When i say weak i mean under a load its weak and is blowing black smoke pretty thick
This would indicate a lack of air to the engines air intake system. Start with the air filter if you haven't already. Make sure it is clean. Even try running the engine, just for a minute or so without the filter in it to see if it straightens up. Sometimes a filter can appear clean, but it is not. If it still runs poorly then check the entire air intake system from the pre-cleaner(where it draws air from the atmosphere) to the turbo charger. Make sure no obstructions. Clean and open air ways. If all is ok, then it is time to check the turbo charger. Quick and dirty here is to pull the air intake pipe off turbo then reach in and spin the compressor wheel. Engine shut down. Not running for safety. Turbo compressor wheel and shaft should spin nice and free. It may be necessary to pull the exhaust pipe off of opposite side of turbo at this point, so that you can reach in from both ends to make sure turbo shaft is not broken. You should not be able to spin both sides independently. This is a decent amount of work for now. Let me know how you make out. Good luck
Or it could be the hydraulic system pump control not responding correctly to the imposed hydraulic load on the machine. Having said that though, checking the basics on the engine as suggested above would be a good starting point.
OR, do a boost pressure test under load. Less writing that way
My long winded suggestion is based on the notion that possibly you are not familiar with checking turbo boost pressure and/or do not have the tooling to do so. A thorough inspection of the air intake system based on the complaint can be done with some basic hand tools.
Exactly, no argument from me. Either way does mostly the same thing. The original poster hasn't been back though, so we'll probably never know how this poor machine fared in life.
Yeah I think we may never know. Nige definitely had a good suggestion about the pump regulator. If it's not destroking the pumps to match with available engine hp then it is going to load up and bog down no matter what power is available.