I have an old Kobelco K903B with some issues. First problem: The engine stalls pretty easy when lifting heavy, using several functions at a time, or just when crawling slightly uphill. Even with the engine on full throttle it wil easily stall if i am not being carefull with the load or speed on the hydraulics. Is there an easy fix to this? Could it be as easy as a clogged filter somewhere, or is it worn out/weak hydraulic pump or engine? Second problem: When moving the arm/bucket towards the cabin, about halfway the arm stops for a few seconds and then suddenly continues. Even if the control is held in the same position. Also when moving the arm against the cabin, it will take some time after hitting resistanse (rocks/earth etc) before it has pressure to continue to push. The arm cylinder has been checked, and has gotten new gaskets everywhere. What is causing this problem? Is there anyone that has a theory on these problems that could help me out? (I am not really experienced with excavators and engines, so please be patient if there is something i dont understand.)
Good day Problem No.1 I would suggest the majority of this common post relates to the engine, often the fuel system has suffered water or ingress from low quality fuel. I would recommend that you service the engine if it smokes under load the color of the smoke can give a clue. Change filters, including the air cleaner, if the fuel system has a strainer in the tank be sure it is clean and not restricting fuel flow. Problem No.2 If you are digging fresh air it is not so unusual that the arm hesitates, there is a specification for how long it should take. It may be that the two problems are connected if you are not meeting full revolutions. If you can confirm which engine you have i may be able to help some more.(Note C model is that I have information) Kind regards Uffex
Thank you for your answer. I will order a full set of filters and airfilter. How do i access the strainer in the tank, if there is one? I have not noticed any particular smoke under load, so it is hard to say if there is any color to it. Grey smoke maybe? The arm does stop for a few seconds when digging fresh air, and then suddenly continues. But it does also do it when digging dirt or rocks, but maybe when it is a bit closer to the cabin. This makes it irritating when for example wanting to pick up a rock against the dozer blade, because it stops, and then suddenly continues the last piece. Sometimes when it stops when digging fresh air, it seems like it is almost just dangling in the air, if i would go out i would be able to move it back and forth by hand almost. I am not sure if i understand what you mean with which engine. It says Kobelco K903B and has the Isuzu engine fitted.
Good day I suggest you time the arm in the air lets see what the result is, be sure to time from the cylinder movement not when you pull the lever. Follow the fuel hose from one end to the tank be sure there are no kinks or nips, where it goes into the tank is where any strainer filter will be. Im not sure if you can access this from the bottom or tank top. Drain the tank before you try. I asked which engine so I may check those performance details. Kind regards Uffex
Hi again. Having a small service on the machine now with changing filters and engine oil. The dealer sendt med a full filter package and there is one small filter i am not sure what is for. Is this the strainer filter in the diesel tank? Check picture. I also got two wrong filters. The air filter, and a filter that goes in the bottom of the hydraulic tank. (Hydraulic strainer filter?) Does anyone know what part number these two filters should be? I haven't timed the arm movement yet, but i suspect that it uses more time than in the specs you sent above. I also wonder what revs the engine should be on when timing the movement. Anyway, i will change the diesel filter, and also the strainer filter (if that's what it is) as soon as the tank is as good as empty, and we wil see if it has any effect on the engines performance. I also noticed that the airfilter is really dirty. Would that also cause the engine to struggle under load? If so i will have to wait untill i recieve the correct filter to see if it helps.
A quick check you should do is check engine for "blow by". As a diesel runs, there can be a small amount of compressed air that sneaks past the piston/rings, down into the crankcase, where that air is then vented. You will find a vent hose somewhere on that engine where this is vented. There may be a small amount coming from the vent but if it is pushing a large volume of air, that is indicative of engine wear. Basically many people chase their tail with fuel and injection fixes when the core of the issue is a tired engine. How many hours on machine? Indications of an engine rebuild? I agree with above, I would not chase hydraulic concerns until the engine stuff is sorted. Nearly all excavators use special "variable displacement" hydraulic pumps in which there are devices in the system that reduce oil flow to match the output of the engine so when the engine is weak or not performing right, the hydraulics will slow way down.
Thank you for that tip! I will check the airflow coming out of the crankcase vent today. I have no clue what is normal airflow, but maybe i get an indication. I dont know how many hours the machine has, because of a fault with the hourmeter. It says a little more that 2000 hours, but i know that is not true at all. I have no knowledge to say if it has been rebuilt or not, but i would think that its not. I am pretty sure the engine is tired anyways. And if so i guess the only fix is an engine overhaul? Would be expensive for one like me with no experience. I am still going to change the diesel filters and airfilter as i know this, no matter what, will still be good for the engine. Then i will check the airvent from the crankcase and see if there is more airflow than it should be.
A quick video of the air venting will be most helpful for those here familiar with engines. Yes, it is VERY common to sell equipment once it has a serious problem. Remember that for many, machines that are productive and mostly trouble free are usually kept in the fleet. This is why I always say "sold for a reason, find that reason"....
Didn't get to make a video of it, but to be honest i didn'n feel alot of air coming out of the hose. I assume that the hose on the first picture is the crankcase vent hose? I just barely feel any airflow, however there is a small amount of smoke coming out of it. Not sure if the following has a connection, but under the engine there is a small oil leak, see second picture. The oil seems to come from the hole above the bolt in the middle of the picture. From the same hole, there is a significant amount of airflow. This machine was bought from an old man that didn't have the health to even use machines anymore, and he was honest to say that the machine is old and worn, so it needs som love. And also when bying a machine from 1986 (i think) i am prepared that there is significant wear and tear on everything on the machine. It has to be said that the machine works fine for a "hobby" type of use, as i am using it for now. When my project is completed it will most likely be sold again. But if some of the problems are fairly easy to fix before i sell it, i will easy get my money back, or maybe more.
Uh, in that second pic, that really looks like the gear drive for the hydro pump unless I'm seeing that wrong. My concern is if that hole is threaded, it may be the drain hole for the drive oil. Figure that out asap! Running no oil is not good.
Hmm, i didn't think so much about that because when i was looking up through that hole i thought that i could see daylight coming through. Have to check this closer of course, but if it is what you say, then what oil does it run on? I can't find anything in the specifications about that.
I cannot be certain at all. Don't let me lead you down the wrong road. But on most excavators, the engine output shaft (crank) mates to a gear box that is filled with oil. Possibly better pics or even books would be helpful. In any case, does the engine breather come out the top as in your pic? If that is the case, it would be worth taking that hat and filter off so you can get a good perspective of how much air comes out. If it is minimal and you just see a little smoke there, that is totally normal and a good thing. Next with any diesel is to evaluate heavily on the exhaust smoke. Does the engine fire right up without delay? Is the smoke black or dark at start up or white-ish? Does the smoke clear? If at any point during running either at idle or load, the smoke is more white, that is telling of an engine issue. Could be lack of fuel, could be injectors, etc. Hard to say but the smoke is the first thing to examine. You need to open the bottom drain of the fuel tank and determine if and how much water is present. Then move to the fuel/water separator. If the engine is picking up some water, water does not burn and will create all the issues you are seeing. You should also smell the diesel coming from the tank drain. Bad fuel certainly has a different odor. Some people ask, "what does bad fuel smell like?".....Oh, you usually know.
About the hole where the oil is coming out, it is not a threaded hole. The picture below is taken from the top of the hydraulic pump towards the engine. There are three big holes, one above the pump, and one on each side, that leads to the same "space" as the small hole underneath... So i guess the oil leak is either from the engine, or from the hydraulic pump. I suspect the engine, as it looks like engine oil. In this video you can see that i opened the hat on the engine breather. There is some smoke coming out, but the airflow is just barely possible to feel with my fingers. The engine is a bit hard to start when it is cold. It always starts, but needs some time. When it is warm it starts straight away. With cold start there is some smoke, as seen on the video, but the smoke clears, and the only smoke that comes while running the machine, is the smoke from the engine breather. Haven't had the possibility yet to investigate more of the diesel. I heard someone say that they seemed to remember that theese machines had bad fuel pumps, could that be a reason for it to stall under load?