I have a Hitachi X 75 you are excavator I gave it a full tuneup the other day I have never had a problem with lack of power nor stalling. Just to give background I changed oil I change the oil filter the fuel filter the air filter and stupidly left the fuel wrench under the machine and it shredded the belt I went and replaced it by pulling the alternator so I could get to everything putting the belt around everything reinstalling the alternator and refilling the coolant because I had to take the hoses off to get to everything as well. After all this I did some work for my neighbor maybe six hours total. The day after that I was removing a stump I had just gotten it out of the ground and when I went to use any hydraulics it started to slowly stall. I immediately stopped using the hydraulics and stopped touching the levers and it stopped bogging down. Then I limped back to my driveway from my backyard just going really easy on the machine and didn’t have any trouble today I went to just go move a couple of trees I had taken down and for the first three or four minutes the machine was 100% fine then the second I really put it under load not just raking branches back but actually picking up some thing kind of heavy it started to bog down again. Again I stopped all controls and it came right back. The best I can tell is when it is under a very stressful load it starts to bog down and the engine starts to sound like it’s going to stall. Whenever I immediately stop controls it stops the engine from bogging down. I have read some stuff about fuel lines being clogged etc. and I thought maybe it could be some thing like that however I feel like if that was the case I wouldn’t have been able to really work the machine hard for six hours the day after I did the tuneup. I haven’t run it enough to see if it’s actually associated with the swing motor or what specific control it is. I will note however after having the machine for almost 2 years when I did the tuneup the other day I pulled the oil dipstick for the swing motor and it appeared to have double the oil that it was supposed to I also checked it cold and I checked it warm it read the same both times. I hadn’t done anything with that quite yet because I said to myself after two years maybe somethings wonky or maybe it’s not the original oil dip rod. I just started a business two months ago and things are finally starting to pick up I’ve actually won a really decent bid where I’m going to make a decent amount of money the day after tomorrow. Now I’m scratching my head wondering to myself why of course now does all of this happen. I am totally open for suggestions on where I should start looking I am usually pretty handy with a wrench coming from a default of course of not being able to afford to pay anyone. I’m wondering if it’s the hydraulic pump starting to fail I’m going to test it a little bit more tomorrow to see if I can isolate if it’s a specific movement that makes the engine start to bog down if it’s the swing I am assuming that prolonged excessive amount of oil in the swing motor could potentially be the cause and maybe I need a swing motor but at this point I’m not really sure where to start do I start with the hydraulic pump, the swing motor, The actual motor all I really know what this point is my business is finally starting to pick up and I’m making enough money to be a single dad and be present in my daughters life and now my machine decides to start acting funky. Any information or any ideas would be so greatly appreciated. I will make sure that I am diligent in checking this post afterwards to try and answer any questions I can for the people who constantly give me advice and in my opinion rock LOL. I appreciate you all on the form so very much! Thank you in advance.--
First thing I would be looking at is every electrical connection at the front of the engine and everywhere near there. When you lose a belt sometimes it can slap the wiring around and knock it loose, or even break a sensor. Have you stalled the engine over hydraulic relief to see if it attempts to stall? We need to determine if it is an engine or hydraulic problem.
how do I do that test? stall over hydraulic releif? I'm going out now to check wiring and see if I can isolate stall related to certin movment. will check back in soon.
so I jiust brought it up to normal operating temp and now its not acting up...... SMH. I took some picks and it appears that there is asensor that is not hooked up to the motor I wonder if it ever was? I took some pictures.
Looks like engine oil pressure switch disconnected but this would not cause stalling. To stall over relief bring the arm in all the way and then keep level pulled all the way to build pressure in the hydraulics. Your problem sounds fuel related to me. Seeing as you had just serviced it if it were me I would be double checking fuel filter seal, O ring, breed screw etc