Forklift tech

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    Forklift tech

    A friend of mine has a Mitsubishi forklift, a FGC25. Over time the lift and tilt have been losing power. Motion became jerky and motor had to be revved.

    Thinking the pump was bad, he pulled it. Internally it looked fine. No scoring in the gears or housing. Turns freely and smoothly. We could not find a filter for the hydraulic fluid, which is surprising. It did have fluid.

    Any suggestions?? Thanks.

    #2
    bypass valve getting stuck open?

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      #3
      air in the system?

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        #4
        What kind of pump? Gear variable piston vane? Get out your ir gun have your buddy run the fucker hot and see where the system is getting hot at?

        I would bet money there is a stainless screen on the suction side in the tank.
        Last edited by ThePanzerFuhrer; 06-30-2020, 04:16 PM.

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          #5
          Cylinders could be bypassing, probably start with the tilt, tilt it all the way out, crack the rod end line, give it more tilt and see what happens

          does the mast drift down with a weight on it?

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            #6
            Another vote for suction screen in tank clogged

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              #7
              Originally posted by SLOWPOKE693 View Post
              bypass valve getting stuck open?
              In on of the cylinders? This happens at all times. Once the lift or tilt cylinders move, they stay where they are.

              Thanks.

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                #8
                Originally posted by RUGER View Post
                air in the system?
                How can I check? Thanks.

                Comment


                  #9
                  Originally posted by ThePanzerFuhrer View Post
                  What kind of pump? Gear variable piston vane? Get out your ir gun have your buddy run the fucker hot and see where the system is getting hot at?

                  I would bet money there is a stainless screen on the suction side in the tank.
                  It's a gear type of pump. When we took it apart, the gears and the housing looked pristine. No sign of scoring anywhere. We didn't check clearances.

                  My friend was concerned that the pump spun too freely. I'm not sure how much drag or preload these things are supposed to have.

                  I haven't found any type of filtering for the hydraulics. I'm sure there is some sort of screen in the tank outlet, but for the life of me, we can't find it.

                  Thanks.
                  Last edited by Mikel; 06-30-2020, 07:37 PM.

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                    #10
                    Originally posted by Projectjunkie View Post
                    Cylinders could be bypassing, probably start with the tilt, tilt it all the way out, crack the rod end line, give it more tilt and see what happens

                    does the mast drift down with a weight on it?
                    No drift on either cylinder as far as I can tell.

                    My friend blew compressed down the inlet to the tank and the air does blow into the tank (I assume a clogged screen would allow air to go the other way).

                    Then he blew compressed air down the high pressure line (from the pump) and the air also went into the tank. I pulled on the levers while this was happening and there was no change - air kept going into the tank. I'm assuming these valves are direct acting, so wouldn't the air be going to the cylinders?

                    Thanks.

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                      #11
                      In order of what I would check. Suction strainer on feed to pump, relief valve most likely located on valve stack, and last the pump. If it's a gear pump don't just look for scoring and gear wear, but also inspect the thrust plates and try to find specs to measure against.

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                        #12
                        It was the pump. Thank you all.

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                          #13
                          Originally posted by Mikel View Post
                          It was the pump. Thank you all.
                          Your not supposed to reply with the solution, it's supposed to be open ended so future searchers with similar problems have no idea what it was and if it was ever fixed.


                          Anytime I search about an issue I'm stuck on it seems that way.

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