Hello all I have read a lot of old posts about this but still need some help. I have a gray market Hitachi ex120. It runs fine at idle but as soon as any hydraulic function is activated it drags the engine down and just about stalls it. I have cleaned all banjo screens, replaced all fuel filters, and changed the lift pump. It has a new turbo. The air filter is new and intake tube clear and not collapsing. The EC motor and control circuit has been replaced with a hand throttle. I disconnected the fuel tank from the engine and ran it off new fuel in a 5 gallon can with all new hoses. I have doctor EX and at idle and hydraulics in neutral everything seems ok. Once and hydraulic circuit is activated the requested pump angle goes to 23.5, almost maxed out, and actual is a dead match. It seems it's doing what it's asking for. My question is should the pump be maxed or is something giving the P.V.C. bad info and it's calling for it when it should not be? any and all info would be appreciated.
I have a John Deere 490e, which is basically the same as an ex120 other than a JD engine. I am kind of a newbie, but I can share the causes the manual says to check when having the engine bog down easily: Do you have manual control over your engine? On my machine, I can switch the engine to max power prior to using any function, are you able to do that? If so, how does it sound? I read through the manual a bit for your specific question on what angle the pump should be at and was unable to find an answer, sorry about that. It sounds like the pump angle sensors are supposed to rapidly adjust the angle based on loads and gives troubleshooting processes for doing that.
This is the full wiring diagram if that helps with the post above.
Also, I am continuing to read the manual and just found this for the connector... I am unsure how to interpret it yet though...
Scary theory: everything was working properly before I screwed with it and the fault code was from the battery disconnect switch I installed a while back. See below theory of operation which mentions after a battery disconnect max power needs to be selected again to reset the power settings:
Did this problem start after E C Motor was replaced with hand throttle?
Steve I'm not sure how I added my reply to your question lol. It worked fine all last summer with the hand throttle. It sat for about 3 months over the winter, and then when we ran it for the first time this spring it started doing it.
Thank you so much for this info. This machine is grey market and hard to get info on. I have a manual for it but it doesn't have any of this info in it.
Any sigh of any Rodents making a winter home in your machine they like chewing on wiring harness?
not any in the pump control wiring. I traced it all out and looks ok. I have DR EX and can watch pump functions and controls. There are no codes in the computer.
Pressure Relief Valve: Check the pressure relief valve in the hydraulic system to ensure it's not malfunctioning or set too low, causing excessive load on the engine. Load Sensing System: Inspect the load sensing system, including the pressure compensator, to ensure it's functioning correctly. It should adjust pump output to match the required load, preventing overloading. System Calibration: Consult the equipment's service manual or a hydraulic specialist to recalibrate the load sensing and pressure compensation systems if necessary. Professional Diagnosis: If issues persist, it's advisable to consult a qualified hydraulic technician to diagnose and repair any faulty components accurately. Incorrect pump settings can indeed lead to excessive load and engine strain.
Did you solve this?
Did you ever figure out what was wrong with your ex 120 I have one doing the same thing and it has a manual throttle also
I did, it was due to a wire to a sensor on the hydraulic pump being broken. If the sensor didn't report info, the hydraulic pump would default to fully open and bog down the engine. Fixing the wire fixed the bogging issue.