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Thread: Excavator lack of power- hydraulic issue or engine?

  1. #1
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    Excavator lack of power- hydraulic issue or engine?

    I just bought a 96 PC50uu2 excavator that seems to have a lack of power issue. We noticed it when trying to push our stuck dump truck out of a ditch, the truck is a small ford f800 five yard that was empty at the time, and the excavator couldn't do it, it would not spin the tracks, just seemed to not have enough power. This size machine should push that small truck out of that situation no problem. We tried putting the bucket against the truck and pushing with the tracks, no dice, then we tried pulling the machine close to the truck and pushing with the boom, no dice,..... so the power issue does not seem to be isolated to the tracks or boom. Also noticing it does not have the power it should when digging. It is an older machine but it should have more power than this.

    First thought was hydraulic filter, changed that along with fuel and air filters. No luck. We are running the machine at full throttle. Does this sound like a hydraulic problem or engine output? No dealer in my area to take it to. Any ideas could I get the hydraulic pressure tested?

    thanks very much

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    It sounds more like a problem with unreal expectations. What frame of reference tells you that the machine should have more power?

    All you can do is check the hydraulic pressures and cycle times. I don't have either specification here with me but many times you can check other machines of the same size for a general statement on cycle times. I know for instance that standard cycle time for boom up in larger excavators is around 4 seconds. If your cycle times and pressures are at factory specification there isn't a problem with the machine.

    Your machine is pretty old speaking in mini excavator terms. It is also a gray market machine. I haven't looked at one of those in years but as I recall they even had gear pumps.

  3. #3
    Senior Member Hendrik's Avatar
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    Your relief valves may be out of whack.
    Can the machine lift itself off the ground?
    Is the engine bogging down as you are doing heavy work?
    A 5 tonne machine should have a fair bit of grunt but the tracks are protected by relief valves to prevent damage to the tracks.

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    Senior Member Chris5500's Avatar
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    I somewhat agree with what John has to say.

    Since you havenít really given us a definitive path to go down or any conclusive evidence that it is actually under powered then all you can do is check some values and compare against the specs to determine if there actually is any problem with the machine's operation.

    For example, engine rpm @ high and low free idle, engine rpm @ full load, main relief pressure, secondary relief pressure, ppc pressure etc

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    Yeah It may be unreal expectations, but our operator who runs these things all the time says it is way underpowered compared to the bobcat 8k lb machine he normally runs, and this thing should out power a bobcat 8k lb machine. Also when trying to push the dump truck out of the ditch it would not spin the tracks, it just bogs, the machine even stalled a couple times when digging rock, is this normal? Maybe the pressure relief valves are out of whack? How can I check this? What should the hydraulic pressure be? Yes the machine will lift it self up off the ground. Where can I find a repair/shop manual for this grey maching?

    thanks for all the help

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    Junior Member in_the_field's Avatar
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    well if it stalled the hydraulics are fine, maybe even to much pressure. i would look at the engine.

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    OK, what should I look for, I guess I need a mechanic.

    Thanks

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    What would make you think a 10,000 pound machine would have more ground power than an 8,000 pound machine. They are basically all designed so they don't have enough power to spin tracks as that wears them out.

    Excavators are not dozers. The travel function is set up to move the machine from place to place. The phony blades they put on them are designed to fill a ditch back in and nothing more.

    Operators are generally not the most reliable people to believe when it comes to the production of the machine. The factory has specifications which are specific benchmarks on machine performance. In this case pressures and cycle times.

    Find a good mechanic. He will become your most important asset in the future.

    Good Luck!
    Last edited by John C.; 04-28-2010 at 08:58 PM.

  9. #9
    Junior Member Lloydsdesignz's Avatar
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    most likely an engine problem. check the fuel lines, diesel filters and banjo's.(that is if the engine stallsand the machine docked for a long time?)

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    Yeah I am just going off what my operator said, he normally runs the 8k lb bobcat and says it would have pulled the truck out no problem, I guess I will use it for a while and see what I think.

    What are the Banjos?

    Thanks

  11. #11
    Senior Member Wardiker's Avatar
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    I had a similar problem with my 1991 Hitachi EX60, It turned out to be a clog in my fuel line, I did check the banjo fitting 1st though. there were several banjo fittings and the one with the filter was hardest to get at (but not that hard). Ive also been told that in some cases they have found a rag in the bottom of the fuel tank, so I removed the tank and pressure washed it to make sure there wasnt dirt at the bottom were the fuel lie connects (and there was) . it was upon replacing the fuel line that I found the clog. Check my posts for more details. And google bajo fittings to see what they look like.
    Dont waste 20 minutes to figure out how to do a 10 minute job 5 minutes faster.

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    Senior Member Hendrik's Avatar
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    Quote Originally Posted by 707pc50 View Post
    Yeah I am just going off what my operator said, he normally runs the 8k lb bobcat and says it would have pulled the truck out no problem, I guess I will use it for a while and see what I think.

    What are the Banjos?

    Thanks
    They are musical instruments played by hill billys, they may also refer to fluid fittings used in fuel systems and others.
    Banjo type 1 https://catalog.foothilloffroad.com/...id=nrlzpdwpknp


    Banjo type 2 YouTube - Deliverance - Banjo Duel

  13. #13
    Senior Member Hendrik's Avatar
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    Quote Originally Posted by 707pc50 View Post
    Yeah It may be unreal expectations, but our operator who runs these things all the time says it is way underpowered compared to the bobcat 8k lb machine he normally runs, and this thing should out power a bobcat 8k lb machine. Also when trying to push the dump truck out of the ditch it would not spin the tracks, it just bogs, the machine even stalled a couple times when digging rock, is this normal? Maybe the pressure relief valves are out of whack? How can I check this? What should the hydraulic pressure be? Yes the machine will lift it self up off the ground. Where can I find a repair/shop manual for this grey maching?

    thanks for all the help
    By 1996 most excavators have evolved enough to have enough engine grunt to work the hydraulics and open the relief valves.
    Hitachi are pretty good at building an excavator and I would say with some certainty that you have a lack of power from the engine.
    Is the engine smoky/hard to start?
    Last edited by Hendrik; 04-30-2010 at 07:25 AM. Reason: can't spell

  14. #14
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    it is a pc50uu2 komatsu not hitatchi, engine starts easily, a little smoke when working it hard?

  15. #15
    Senior Member Hendrik's Avatar
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    Quote Originally Posted by 707pc50 View Post
    it is a pc50uu2 komatsu not hitatchi, engine starts easily, a little smoke when working it hard?
    What colour is the smoke?
    If it is black that is pretty normal but other colours are not.
    Not really sure why I thought the machine was a Hitachi, perhaps I was thinking of another thread however design wise they are all pretty much the same.
    Has it been suggested that the strainer in the fuel tank is blocking up (if it has one).
    Many years ago I had trouble with a 1075 JD harvester, all season it felt like it lacked power, changed the main fuel filters, put on a new main drive belt but she still didn't feel right. Towards the end of the season I found that someone had put on an aftermarket fuel pump, right down the bottom and behind the tank (in order to pump more fuel up to the engine). This aftermarket pump had an integrated filter built in and it was all clogged up.
    Once that was cleaned the machine ran like a Deere should.

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