I have a Hitachi 120 that dies out from cold when you operate the hydraulics. It is definately not a fuel problem, so that is ruled out. Looking at other forums on here, I thought it might be the angle sensor, so I replaced the angle sensor. I think that I adjusted the voltage right, but it made no difference. In fact, in thinking that I had adjusted the sensor incorrectly, I just moved it to random positions and there was no change whatsoever. The machine cuts out when you operate hydraulics from start up. It doesn't have to be hot to cut out. The sound that the pump is making is almost like it is running low on fluid, but it has plenty going to the pump. Any idea on what is going on here?
Hi there, Sounds like pump solenoid. Swap solenoid's around and see if hydraulics go slow instead of stalling engine. Be sure to swap wires too.
I'm having the same problem my hydraulics are slow if I swap out the wires on the solenoid the hydraulic s work fine but if I do more than one function it stalls out the system we have replaced one solenoid and a PVC controller with no help we have ordered a DP sensor. Any help is appreciated
Would be interested to learn the resolution to this problem. My hydraulics become slow after about 30-40 minutes of run time; engine still runs fine/normal, just slow hydraulics. (Hitachi EX120-2).
I will hopefully
Have you looked at the pressure sensors on the pilot hydraulics? They could be cracked and shorated or broken circle u it keeping the pump in full wash. Also, like was mentioned, check the pump solenoids. Swap the plugs around and see what happens. Additionally, are you positive it is not fuel related. I had an issue where I thought it was not fuel related and it ended up being that the throttle cable was getting hung up starving the engine for fuel.
@knightgang - Do you think my issue could be related to fuel? See symptoms at this link. Currently I'm the last post.
Dsharp ,it sounds to me like your oil is getting hot and thinning out. This might be causing a bypass problem some where in the system
@Bls repair - Any idea what would be causing the hydraulic oil to heat up?
Just using the machine will heat up the oil
hey guys, theres a small control Valvebox that controls the pilot circuits and its got a bunch of solenoids. Make sure you change the o rings on these solenoids and the seals. Theres one there which can cause various issues with slow hydraulics to oil heating up cuz it makes the pump angle more and more heat is dumped from the excess pressure. We tried everything with a 120-2 and in the end only thing that fixed it was once we completely resealed the small control Valvebox. All the o rings and seals had had it in that.. Other things that almost always leads to heating up is the DP sensor. get a box cuz the Chinese made ones last 1-6mnths and some are dead on arrival!
@digger_hunter - I attached a diagram of the hydraulics for the EX120-2. Are you referring to the "Solenoid Valve Assembly" in the diagram?
yeah thats the one!
basically theres a bit of a giveaway not sure if I am 100% correct. But you can kind of feel the pilot line pulse like 1 x each second due to the pilot solenoid in that Valvebox relieving the pilot pressure. But the machines that heat up tend to have this pulses more widely spaced or not at all.
let me know if you want the service manual
Can you send manual for hitachi ex120-2 my email is [email protected] pls thanks
Did anyone check the controller fuses? If one of the PVC fuses is blown it will stall hydraulics when operated. You may lose engine rpm control with that as well?? Also when the DP sensor was replaced was the little spring in there that keeps the DP shaft from flopping around in the pump feedback shaft? Like sk120 said, swap solenoids or wiring to see if there is a change. Those solenoids have a history.
One thing that most people overlook is the pilot pump it self. When they wear they continue to pump pressure but the flow drops off. The lack of oil causes the valving to only partly open and the engine to labor
Hey there, do you by chance still have the service manual for the hitachi ex120-2? Having some hydraulic issues. After about 2hours of running fine it starts to loose power and hydraulics (all functions) start cutting out. Lots of chatter around the valve control area. Did you have similar issues with yours before making the repairs? Thanks
Hey there, do you by chance still have the service manual for the hitachi ex120-2? Having some hydraulic issues. After about 2hours of running fine it starts to loose power and hydraulics (all functions) start cutting out. Lots of chatter around the valve control area. Thinking the issue may have to do with the pilot
@LACHAU posted a link to a EX120-2 service manual in the thread below, see post #9 .