1996 HITACHI EX120 will not travel

[Hammer49]

I have a EX120.It was working fine then one day it would'nt move.Either track, no forward or reverse.And when i work the foot pedals the engine speeds up and the machine tries to move but only moves like one inch.After reading a lot here and with the technical Manual.I would like to know how to check the Signal Pilot Pressure Circuit.I'am thinking this could be the problem.When trying to travel it sounds like hyd fluid is trying to flow but something or some valve is not opening.Also could it be electrical like a fuse.And what tools wood i need to check it out.
Thanks for your help.

 

[rgl726]

how about the upperstructure. are they normal?

 

[Hammer49]

Seems a little slow.Now that you mentioned that I could'nt even move the excavator while working the travel pedals and the boom/dipper to drag it forward or back almost like the brakes where not released.

 

[rgl726]

if all the function is slow. here what to check.

1. check the pilot pressure. it should be at least 750 psi.
2. replace the dp sensor with a new one.
3. check the angle sensor.

do this this steps and tell me the results.

 

[Hammer49]

Thanks
Differential Pressure Sensor what 2 pressure does it check between.and the same for the angle sensor.where is it located,what does it do too.I guess i need a 1000psi gauge to check the pilot pressure.does any one have pictures of where the 2 switches are and a procedure on how to check them.my manual doesn't show me how to check them. your help is much appreciated.

Thanks

 

[Anto Modded]

On our pc130, (i know its not hitachi) but it stopped tracking and the computer said it was solinoids i think. We were told to take out like screw in fuses and clean them and put them back in and it worked perfect. Sorry my part discriptions arent great

 

[rgl726]

Thanks
Differential Pressure Sensor what 2 pressure does it check between.and the same for the angle sensor.where is it located,what does it do too.I guess i need a 1000psi gauge to check the pilot pressure.does any one have pictures of where the 2 switches are and a procedure on how to check them.my manual doesn't show me how to check them. your help is much appreciated.

Thanks

DP sensor , is the can shaped sensor on the top and in the middle of the control valve. This tells the computer the difference in pressure between what the pump is putting out and what the valve bank is using.

Angle sensor, the small can shaped sensor on the side of the hyd pump, this monitors the angle of the swash plate inside the hyd pump to tell the computer how much oil the pump is tying to put out.

dp sensor is located at the main control valve and the angle sensor is in the main pump.

 

[Hammer49]

Thanks very much for that information.Now that sheds more light on the problem.I will check those sensors.Thanks to raymond for sending me the diagrams too.

 

[Hammer49]

Can anyone explain to me what the pilot pressure actually does.

 

[cps]

I hope you dont think im talking crap here, but is it cold with you at the minute? The reason i ask is i had a customers machine a few weeks ago that had so much muck around the tracks that had froze and was giving the same systoms as yours!

May not be the case with you but just a thought!

Aiden

 

[Hammer49]

yes its cold here,but the tracks have no muck on them and they are clean.thanks away

 

[rgl726]

Pilot pressure is the one driving all your control stick signal, pump swash angle and solenoid valves.

 

[Hammer49]

ok I think I got it now.its like the hyd link to the controls.Like a gas pedal linkage is to a carburetor.


Thanks Guys

 

[Hammer49]

A little update to the problem i had with the travel.i finally got this do to move. by moving the boom and dipper levers back and forth and letting them go to the neutral position it would start to move but seems jerky like it has no power.when it would stop moving i would move the levers again back and forth fast and let go to neutral and it would start to move again.and would move on level ground.Seemed like i play with with boom/dipper levers it would stop moving sometimes,if i stepped on the left or right forward pedal it wouldn't turn.If I used both to start then use one and it still wont turn unless your going down hill.seems like all hyds have no power,dipper and boom also slow.I can use the bucket to help me turn but will not turn without the bucket help.changed the travel pressure switch and hyd filter and that didn't help.do you need special tools to check for trouble codes.

 

[digfaster]

check th relief on the boom and swing function. its on the bottom of the valve body second from the left i believe. i had a similar problem, turns out it was a broken spring in the relief

 

[Hammer49]

Thanks I will check that out tomorrow.have nothing 2 lose.Also Does anyone know where to get a diagnostic code list from for a EX120-2.

 

[tool_king]

Hammer49
Download this link and check out page 125 .And the meanings are page 156.Hopefuly it helps.
http://www.4shared.com/document/YpCqdWo0/TTLA0463_Performance_Check.html

 

[Hammer49]

WOW,Thanks Tool_king that is AWESOME.Great document.Once again Thanks

 

[Hammer49]

Hi Tool King,
I switched the wires on the solenoids on the main pump.and the machine had awesome power and moved great,but the engine would start to choke out,black smoke out of the exhaust,when tried to do 2 functions like {boom/travel}probably because the pump is at full power.I checked the both solenoids with a ohm meter and got the same reading for both 18 ohms. Is it a solenoid thats bad or is it something else that would turn on that solenoid.So what do those solenoids do??.checked for codes and have none. when i listen by control valve it sounds like a loud hissing almost like one valve is open and one is not.like the fluild is trying to move but a valve is half way open.Maybe a solenoid on the on the control Valve?Something is not kicking in that solenoid or its bad. How to do you check the solenoids. Thanks Again for your help.

 

[Hammer49]