How to Fix a Hydraulic Dump Trailer System

DumpLine4 - Hydraulic Dump Trailer SystemFelling Trailers manufactures hydraulic dump trailers ranging in capacities from 4,500 – 30,000 lbs. Each trailer has a hydraulic pump system that operates the raising and lowering of the hydraulic cylinder or hoist that raises/lowers the dump box. If your Hydraulic Dump Trailer System is not working properly, we are here to help. We recently talked to our Warranty Coordinator, Scott Brown, to get his expertise on fixing hydraulic dump trailers. Below are some troubleshooting tips for issues that may occur with the regular operation of a hydraulic dump unit.

Trouble Shooting Hydraulic Dump Trailer Systems

My hydraulic dump trailer is leaking fluid, what should I do?

Safety Prop in Place-Felling - Hydraulic Dump Trailer System

Always have the safety prop in place before inspecting the dump trailer.

Before inspecting for leaks, make sure that the box is up. Always use the safety lock bar to hold the box up. View the Operating Instruction Felling Hydraulic Dump (PDF).

What is the leak caused by?

Typically any leak is caused by a battery with a low charge. The weight of the box is putting pressure on the system so as the box is lowered, the pump can’t keep up with that pressure due to the low battery. Then it creates excessive pressure causing the oil to blow out of the breather on the tank. We have seen some cases that the breather is plugged with so much dirt that it creates excessive pressure and cracks the tank. It is advised prior to the use of the hydraulic system to look over the unit and ensure it is free of debris and dirt.

I am having issues with keeping the battery charged. What battery chargers do you recommend?

There are some very useful battery chargers that can help. Be aware, however, that to charge your dump trailer system, the tow vehicle has to be running and the headlights need to be turned on. Both examples below can be purchased through Felling Trailer’s Parts & Service Department at 866-335-5464 or email at [email protected].

Email Felling Parts & Service

Trickle Charger – Trickle chargers are very convenient because they allow you to always start the day with a fully charged battery. Click here for more info on a trickle charger.

Solar Panel Charger – The solar panel charger is also a great choice. If you don’t use the trailer every day, you can be assured that when you do use it, it will have a fully charged battery. Click here for more info about how the solar panel battery charger works.

How many cycles can an average dump trailer run before the battery is depleted?

If you are doing short runs between cycles – approximately four to five. If you are driving 100 miles between cycles, then you would probably get more, since the additional distance would allow for more charging time for the battery.

Order Parts Here

The hoist is stuck in the dump position, what should I do?

Square Coil - Hydraulic Dump Trailer System

Square Coil

Round Coil - Hydraulic Dump Trailer System

Round Coil

Looking down on the pump there is a square-shaped coil (down) and a round-shaped coil (up), generally, you can loosen the nut onto each coil and swap them around, which then allows you to lower the box. It is possible to continue to haul with the trailer this way by swapping the coils around until the new one arrives. Note: This is a temporary fix until new parts are received to replace the defective parts and/or pump.

After my unit is fixed, what type of hydraulic fluid should I fill it with?

Fill the tank to approximately half full. The type of hydraulic fluid should be automatic transmission fluid.

If you have more questions regarding the hydraulic pump system, or maintenance or operation of another Felling Trailers product, please don’t hesitate to contact us at 1-888-335-5464 or fill out this simple form. Thank you for putting your trust in Felling Trailers!


  1. I had no idea a leak with the hydraulic system could simply be caused by the battery not being fully charged. I guess it makes sense, if the battery isn’t charged enough to support the press, then the pressure will build till the oil gets pushed out. I will have to tell my friend who has a dump trailer about this so he can keep it running smoothly. Thank you for the information!

    • Jose aguado says

      I have a trailer the battery seems is sufficiently charge but when I try to lift it the pump will not run,any idea of what the problem could be?

      • Good Morning Jose,
        The pump should have a relay mounted on the outside of the motor. I would try jumping that by taking a wire and touching both large terminals. This will bypass the relay which if the pump works then the relay will need to be replaced.

        Hope this helps,
        Felling Trailers

  2. my trailer will not raise and I’m have a lot of oil coming out of the rear in of the cylinder. I did notice that I had a low battery at the time. What is going on here ?

    • Felling Trailers says

      Hello Dennis,
      If its leaking at the cylinder I would guess a blown seal on the cylinder.
      The other thing to watch is if the battery is low and you are lowering the box down, the pump is turning so slow that with the weight of the box pushing down on the pump it creates pressure, which typically the oil will spray out of the tank fill cap which is also the breather. But if the breather is plugged it looks for a spot to relieve the pressure, sometimes I have seen it actually crack the plastic tank.
      If you have additional questions feel free to call our Parts & Service Department at 1-866-335-5464

      Felling Trailers

      • I have a dump trailer it raises and lowers just fine but when it’s all the way up it leaks down slowly what is the cause for this and how much would you charge me to get it fixed

        • Hello Clark, It could be a hydraulic cylinder or even bad o-rings in on the valve body. If you have more info we could troubleshoot it a bit more for you.

          Hope this helps,
          Felling Trailers

          • I’m having this same issue. Did you figure out or know how to jack it up safely.

          • Felling Trailers says

            Hello Crystal,

            To lift the dump box you can try lifting it up with a loader or jacking it up, which you may need to remove a hose to do so.
            For more information or parts assistance please call 1-866-335-5464 or visit our Parts’ website

            Have a good day,
            Felling Trailers

          • My dump trailer is sending power to both up & down solenoids at the same time…. brand new less then 10 dumps on pump – beyond frustrating can you all help me?

          • Hello Jeff,
            Could be a bad contact in the switch, can he send a trailer vin?

            Hope this helps,
            Felling Trailers

  3. Can I connect my trailer to my trucks charging system with a splice of the large power wire that power my electric hydraulic plow? Since I would never be using them at the same time I figured this would solve the constantly read or under powered battery problems. If I can splice this should I remove the battery in the trailer or connect it together with it?

    • Felling Trailers says

      Hi Eric,
      To answer your question, yes you would be able to do so. This would allow you do dump your trailer without draining your battery. But, I would suggest leaving your battery connected in case something with your charging system would fail.
      Felling Parts & Service Department

  4. Tom Wilfong says

    i have a 10 ez dump trailer and sometimes it will dump just fine and other times it will not it puts presure on it but will not dump. it was working just fine the other day & the next day it was setting at the same place & in would noty dump

    • Felling Trailers says

      Hello Tom,
      I will refer your question on to our service department and get back to you soon.

      thanks much
      Felling Trailers

  5. Kevin Cotterchio says

    Can you give advise? My dump trailer very slowly lowers if I leave it up for any length of time. The battery was low, but I have since fully charged it, but it is still lowering. The rate of lower is about 1/2″ in an 8 hour period. I see no leaks of any kind? What could it be? Thanks

    • Felling Trailers says

      Hello Kevin,

      In reply to your question on your hydraulic dump trailer, I suspect that you may have an internal leak in your hydraulic cylinder or in the pump both of these would allow the oil to pass through with not external leak.

      Felling Parts & Service Team

      • Mine goes up just fine but powers down at about 1/2 speed, it sounds like gobs of air is coming from somewhere when I lower it, everything is tight,

        • Felling Trailers says

          Hello Jeremy,

          Assuming that the battery has a good charge, I would then pull the valve and check the O-ring condition. The square coil on top of the pump controls the down function, you can remove the coil and then the valve will turn out of the housing. Something to keep in mind is that if the battery has a low charge and you lower the box this can cause pressure in the system because of the weight of the box and a pump that is barely turning the system will build pressure and usually shoots oil out of the vent cap.

          Felling Trailers

          • Lorne Gillard says

            I have a dump trailer (my first), and the battery is located underneath and is dead. The battery is in a case, so how do I raise the dump enough to either charge the battery or replace?

          • Felling Trailers says

            Hello Lorne,

            To lift the dump box you can try lifting it up with a loader or jacking it up, which you may need to remove a hose to do this.

            Felling Trailers

  6. Jeff brady says

    Hi, I have a homesteader dump trailer. It has been sitting for a year or so before it was given to me. I put a set of cables from my diesel to the battery because it was dead and wanted to see what it would do. When I hit the up or down button on the the controle the pump motor will run and I can hear what I believe to be the solenoid click, but all that happens is the body will shift a very small amount and that’s it. What could be the issue?

    • Felling Trailers says

      Hello Jeff,
      This is a good question, with your trailer having sat idle for that amount of time there are several factors that may be coming in to play. Read below for some trouble shooting checklists.

      In the case where the start Solenoid just clicks and the system is not engaging, check the following:

      1. Carbon buildup on contacts in start solenoid
      2. Rust inside motor
      3. Loose wire from start solenoid to DC motor
      4. Cracked housing on start solenoid

      For the case where the cylinder won’t extend, you can check the following:
      1.Check Voltage at Start Solenoid when trying to run Power Unit (Voltage May be below 9.5 volts)
      2.Check to see if power unit is bypassing over the relief valve
      3.Improper fluid in reservoir (viscosity to high)
      4.Check Directional Valve Section D/A
      5.Check Packing on Cylinder Section

      Another set of check points if the dump struggles to lift the load:

      1. Low battery
      2. Poor ground
      3. Gear pump sucking air
      4. Directional valve half shifting D/A
      5. Debris in relief valve

      We hope this has been of help.
      Felling Parts & Service Team

      • Thanks for. The great tips on your web site my dump trailer had a bad ground from the solenoid to the frame on the up side.

        • Michael Goodrich says

          Installed new remote for dump trailer, just keeps on clicking.
          Tested battey have13v, tested start solenoid wire while pressing remote in up position, had 12-13v, tested lowering valve coil wire while pressing down button, had 12-13v.
          My remote is 3 wire, power up, gravity down.
          I have worn myself out trying to get my dump trailer to raise, does nothing but click, click, click at lowering coil.
          Motor simply does not engage.
          Dont know if i’m hooking up solenoid wrong, or coil is bad, etc.
          If you can help, would be greatly appreciated.

          • Good Morning Dan,
            If this is a KTI brand pump I would suggest calling the Service Department at KTI, they are very good to work with and should be able to help
            KTI Service Department 949-752-8818

            Hope this helps,
            Felling Trailers

      • How do u adjust the valve if it’s stuck?

        • Felling Trailers says

          Hello Brice,

          I’m not sure of any adjustable valve on the pump that we use here at Felling?

          What is the issue that you are experiencing? With a bit more information we may be able to figure out what you will need to do to get the trailer back in working order.

          Felling Trailers

  7. I have a flo n dump truck that snap’s the connection nut(from the hose to the operational valve) on the bottom of the lift piston while raising .I’m aware THAT THEIRS ROUGHLY 500 PSI DURING LIFT OPERATION YET I HAVENT FOUND A RESTRICTION IN THE SYSTEM TO CAUSE THIS DAMAGE

    • Felling Trailers says

      Good afternoon Kirk,

      The system for a dump truck, dump box is different than that of our dump trailer system. We would suggest to contact the manufacturer of your unit for troubleshooting.

      Felling Parts & Service Team

    • I have a big tex 7×14 dump trailer. It just started giving me problems. It dumps fine but keeps freezing up on the way down like it’s stuck but if I go up and down with the remote it will finally come down

      • Hello Jason,
        Could be losing power to the coil, I would check the connections and make sure they are clean.

        Hope this helps,
        Felling Trailers

      • I have the same problem, terminals are tight and clean. Did you find the issue?

        • Felling Trailers says

          Hi Logan,

          Depending on the brand of pump, there could be a loose or bad wire at the coil. Typically, there is a up and down coil on the top of the pump with two wires running to each.

          Hope this helps,
          Felling Trailers

  8. My trailer is not lifting, though it has no load on it. I thought it was the battery so I bought a new battery, it didn’t solve the the problem. Is there a way I can lift the trailer box so I can check the solenoid?

    • Felling Trailers, Inc. says

      Good afternoon Al,

      You question has been referred to our Parts & Service department and we will have an answer for your shortly.
      Felling Trailers

    • Felling Trailers says

      Good afternoon Al,
      It is suggested to put power to the opposite side of the solenoid and see if it engages. If it does then you will need to replace the solenoid.

      Felling Trailers Parts & Service Department

  9. I have A 5 ton dump trailer, when I lift to dump it works fine but when I bring it down. and it gets to the last cylinder it starts shaking and vibrating while coming down. still comes down but it is very rough and noisy.

    • Felling Trailers, Inc. says

      Hello Jason,

      I have sent your question on to our Parts & Service Team and will have an answer back to you soon.
      thanks Felling Trailers, Inc.

  10. Check the wires in the plug in for the control.One of mine was broke not letting the dump box down because of a bad connection

  11. My trailer lifts up and lowers when it’s empty. But, when it has a load, it will not lift. Any suggestions to help troubleshoot would be great. Thanks.

    • Felling Trailers says

      Good afternoon Jeff,

      I have sent your question on to our Parts & Service Team and will have an answer back to you soon.
      thanks Felling Trailers, Inc.

    • Felling Trailers says

      Good morning Jeff,

      Assuming that this just started I would suspect that the pressure relief valve may be inoperable, and may need to be replaced. To check the valve you will need to hook a pressure gauge to the pump to check the actual pressure which should be 3000 psi. If parts are needed we do have an online parts store, see the following page link to our Hydraulic Dump Trailers
      If you need further assistance please contact our Parts & Service Department at [email protected] or 1-866-335-5464
      Felling Trailers Parts & Service Department

  12. i have a trailer replaced line now it has trouble going up and down and motor gets hot

    • Felling Trailers says

      Hello Jerry,
      Did you replaced 1 line or 2? If you replaced two lines it is possible that you hooked them up backwards, but if you only replaced the one, then I would put a pressure gauge on it to see what the pump is putting out. Assuming that this issue just started, it could be the pressure relief valve or could be a low or bad batter. The longer the pump runs the hotter it gets, so if its just barely lifting and you hold the button down the motor can get real hot.

      Thanks Felling Trailers Parts & Service

  13. My 14′ dump trailer just buzzes when I push up or down it did this often and I would wiggle the solenoid and it would start working the ground had got so hot over heavy use it melted off the plastic covering it now it is just bare wire and it got stuck in up position so I swapped the round and square up down and got it down when I was going to put a new up part on it would not work at all only buzz even when moving the solenoid and ground do you think it could be the ground solenoid or connection of ground to solenoid or possibly something else

    • Felling Trailers says

      Good morning Michael,
      I suspect that it may be the relay, if you jump between the two studs on the relay with a wire and then try it, if it works then the relay will need to be replaced.If you need replacement parts, we do have an online parts store, see the following page link to our Hydraulic Dump Trailers
      If you need further assistance please contact our Parts & Service Department at [email protected] or 1-866-335-5464
      Felling Trailers Parts & Service Department

  14. My trailer spilt all the oil when I tried bring it back down the battery was poor is there something I have to do before putting in more oil???

    • Felling Trailers says

      Good morning Mac,

      If the battery is low and you lower the box it will build pressure and spray out the breather. You will need to re-fill the tank to the mark on the reservoir tank with automatic transmission fluid.

      Thanks much Felling Trailers Parts & Service

  15. Jerald Richards says

    My dump trailer lowers crooked one cylinder is extended about 1 1/2″ longer then the other

    • Felling Trailers says

      Hello Jerald,

      The thing to do is run the box clear to the top in the dump position, then measure the amount of the shaft extended on each cylinder. If that measurement is the same there may be a restriction in the line or cylinder but if one cylinder is extended more than the other it could be a twisted box or hoist.

      Thanks Much,
      Felling Trailers Parts & Service Dept.

  16. My dump trailer lifts fine, even with a full battery it over flows the tank on the way down . If I lift it again it doesn’t have enough fluid to go all the way up. It’s a dual action system.

    • Felling Trailers says

      Good morning Matt,

      Have you checked the breather in the fill cap? You need to make sure that it’s not plugged, if plugged it could be the cause of your issue.

      Felling Trailers Parts & Service

  17. My trailer will lift, but will not hold in the “up” position. It bleeds back down rather quickly, basically like it’s not holding the pressure. It is not a telescopic cylinder. Could this be due to a low battery? Thanks

    • Felling Trailers says

      Hello Mitchell,
      This should not be a battery issue, but without knowing what brand of pump system is on the trailer, it is tough to be sure due to the fact that each manufacturer uses different set-ups. The first thing I would check is to make sure that your oil level is at the recommended running level. Secondly, check all hoses and fittings to make sure they are all tight and that we do not have any leaks in the systems which would allow for oil to leak out. Third, check and see if there might be a backflow/check valve inline that might be bad and allowing oil to flow back through the system. If all of these scenarios look good, you might have to look more into pump issues.
      Felling Trailers Parts & Service

      • Mine does same thing it wont stay up…no leaks

        • Good Afternoon Cody, A couple of questions and I can pass this on to our service department for there advice. What is the brand of trailer. Also what is the brand of the pump that is installed on your dump trailer.
          If there is any other info you can provide that also would be helpful.

          Thank You
          Felling Trailers

  18. Chris Saylors says

    Good Day,
    I have a farm built, dual scissor ram, single pump system. Only one scissor system will work at a time. As the load shifts or if I disable one side the other scissor system works like a champ. How do get both sides to work in unison? Do I need some sort of priority flow control valve installed? If so where in the system and what type do I need? 14′ trailer. My system is a 5gal reservoir tank. It supplies dual 5in D rams(33″L) w/2in D rods each. HPU by Bailey 309-235A DSA1S1602S20H-25 12V 1.3GPM@2500PSI SGL ACT w/20ft remote. Pwr up/gravity down. Thanks, Chris

    • Felling Trailers says

      Good morning Chris,

      What we would recommend is a flow control valve similar to the ones we use on our bi-fold ramps, part number 1001792.

      Felling Trailer’s Parts Department

  19. My trailer will rise all the way up and stay there it will not go down!

    • Felling Trailers says

      Hello Jacob,
      If it’s a Felling trailer you can swap the two coils around on the top of the pump. The square coil controls the “down” and the round coil controls the “up” so if you swap the two around it should come down which if it does and won’t raise then the square coil needs to be replaced.

      Thanks, Felling Trailers Parts Dept.

  20. Glenn Deppe says

    My trailer has been working fine. I had problems last fall and replaced the solenoid and cleaned out the inside of the starter motor because everything had become covered in rust. But up until this morning, it had been running great. On my second load dumping, about 1 foot into the lift, the motor sounded like it had a dying battery. I could hear the motor slowing down. Not wanting to damage anything, I lowered the load and hooked up my battery charger. But my battery was putting out 12.7 volts. I tried to lift, and only got a clicking out of the solenoid. So, I disconnected every contact on both the positive and negative sides and polished them well, still only a click. I pulled apart the starter and cleaned the rust buildup on the inside contacts, still only clicking. I checked my connections and grounds again, still only a clicking out of the solenoid
    Please help me, am I missing something simple? Has my starter itself just finally gone? Is there a way to check it out?
    thank you very much for your time and con

    • Felling Trailers says

      Hi Glenn,
      A quick way to test the motor is to use a good battery and jumper cables. Hook the cables to the battery and then hook the positive cable to the positive post on the pump and then the negative cable to the ground post on the motor. This will bypass everything and just power the motor which should make a squealing sound (it’s not going to pump fluid but should bear down) which if it does then the motor should be good if it does not make a noise then it has an issue. If the motor is bad you can take it to a local electric motor repair shop or call Felling Parts & Service or order online at, a complete new motor/pump.

      Thanks Felling Trailers

      • Will DeLorey says

        The problem I’m having with my dump trailer is that all it will do is make squealing noise when u push up or down and this is when it’s hooked up properly. What could be causing this?

        • Good Morning Will,
          It sounds as if the pump is “deadheading”, possibly the valve is not opening on the pump so the fluid is unable to flow. I would check the coil on top of the valve to make sure that it’s still good. If your pump is a power up and power down, you can try swapping the two coils around, if the box then goes up you would know it’s a bad coil. If the box does go up, you will need to swap the coils around again to bring the box back down.

          Hope this helps,
          Felling Trailers

  21. Melissa Karaliunas says

    How can I lower a hydraulic trailer if it won’t go down and I need to take it for repair?

    • Felling Trailers says

      Good day Melissa,
      If you have a KTI pump, (this is the same pump that we have used for the past 10 years or so) you can remove the round coil, (this controls the up function) by loosening the nut on top and the two wires. Then swap the round coil with the square coil, (this controls the down function located next to the round coil). After the coil swap is done, you can then lower the box. Note: By continuing to swap the two coils, the trailer can be used until you receive the new square coil that is typically the reason why the box won’t lower. These parts can be purchased from our online parts store

      Thanks, Felling Trailers

  22. I hit the up or down bottom
    Motor solenoid just clicks
    Replaced solenoid same problem
    Jumped motor on pump w/ battery same problem
    Up & down solenoid both working
    What are the steps to replace the motor on hydraulic dump lift?

    • Felling Trailers says

      Good day Phil,

      If it’s a KTI pump which we have used the past 10 years or so I would try swapping the round coil and square coil around, the round coil controls the “up” function so it may be just a bad coil. As far as replacing the pump you would disconnect the wires and hoses, then remove the old pump and install the new which should be a fairly simple swap. After the pump swap has been made fill the tank up about half way and work the box up and down which will work the air out of the lines then make sure the tank is filled to the mark on the side of the tank.

      New coil $22.95
      New pump $435.95, order here

      thanks Felling Trailers

  23. Good Morning: I have an Easy dumper trailer that goes up fine, but won’t come back down unless I bleed a line.
    It is power up and gravity down with only one coil.
    Fenner 1787*AC
    12 Volt Pump

    I have changed the coil and changed the solenoid with no luck

    The original problem was I was at the dump, and the bed was all the way up.The hand control was broken, so I had to jump the terminals to get the bed back down( shorted something out?)
    This is after I let someone borrow it not knowing that they broke the controller.

    Possibly the wrong solenoid?

    • Felling Trailers says

      Hello Greg,

      I am not familiar with a Fenner pump, I would have thought that it was the coil, but since you already replaced it, I would suggest having a local hydraulic shop take a look at it or depending on their labor rate you may be better off replacing the pump which runs $435.95. This can be purchased online through our parts website

      Thanks, Felling Trailers

  24. Hi. I have a 2010 7×12 gatormade dump trailer. Its eorked great for me until the other day when at about halfway up, it stopped lifting and started making a horrendous noise. It went back down when I pushed the down button, but wont go back up. Does that sound like its the round coil thats the problem? Is the unusual noise typical in that situation?

    • Felling Trailers says

      Good day Jeff,

      Typically when the coil is the issue, the pump will do nothing. With the noise that you are hearing, I would look at the cartridge that the coils attach to. It would seem like the pump is trying to pump but it can’t push the oil through. To purchase the parts needed, visit our online store

      Thanks, Felling Trailers

  25. Jim O'Brien says

    The 12V wire from the battery to the solenoid heats up so much that the casing on the wire has melted. Also, the wire from the Up/Down controller that connects to the same 12V port on the solenoid also melted and caused the wire to burn off. The cable from the battery is a #2 and the connection is tight.

    Any thoughts?

    • Felling Trailers says

      Hello Jim,

      Typically we see this when the battery is low and the operator is trying to get that last cycle out of the battery before it completely goes dead. The charging wire ends up pushing a lot more amps than the wire is rated for thus heating it up and melting the wire.
      To order the needed replacement parts go to

      Best Regards,
      Felling Trailers

  26. Jake Hambleton says

    My trailer is new this year, works fine but just has a bit of a jiggle on the way down … is this something to worry about ? I typically just take it down extra slow so it doesn’t do it badly, it is a 5 ton dual Cylinder model


    • Hello Jake,

      Would you be able to take a short video of the trailer as is lowering so that it can be compared to other trailers? You can email the video or link to the video to [email protected].

      Felling Trailers

  27. shawn w thayer says

    I have a u-dump trailer that I have been working the bugs out of. If I raise it the entire amount up sometimes it sticks and will not come down until I apply pressure. It returns by gravity. I have cleaned the vent in the reservoir but have had no luck preventing the sticking when raised 100% high.