I have an EX120-2 machine. I bought it with a bad oil cooler, so I wasn't really able to warm it up and test it thoroughly. Now that the cooler is repaired I'm able to warm the machine up and now have a more elusive problem.. The machine is very sluggish after about 10 minutes of use. The machine does make a noticeable hissing from the valve bank, and the pilot pressure line clicks and pulses. It appears that someone has swapped the solenoid wiring as there are witness marks on them and they are swapped around. When I switch them back the machine is quick but is unable to work because it tries to stall under any load. Im interested to know if anyone can pinpoint one of the sensors, or the solenoids from this info? I have checked the fuses, and the wiring is intact from what I can see. All nicely loomed and still clipped. Ive been reading through all the threads on this issue, and Im interested to hear if anyone has had any luck with the mechanical regulator kits, from China, or Hitachi? If anyone has the info from Hitachi that would be great. Im kinda scared to buy any electrical parts because Im affraid the machine may short them. Its hard to replace electrical parts not knowing why they were fried.. Thanks! Been very helpful reading through all the stories on this issue.
Sounds like a bad pump displacement solenoid.Take the solenoids off and swap them.One solenoid strokes the pump and the otherdestrokes the pump.This is a grey market machine and they had a few problems.This was Hitachis first foray into computerization and it . was either so jerky it would throw you out of the seat or it was a dog.Also check the wiring to the pump displacement solenoid on the side of the pump.The pilot pressure line clicking is normal(relief valve)
So if I swap the solenoids and the machine becomes jerky it's a safe bet that a solenoid is bad? Is there a good way to test them?
if machine function changes when the wiring is swapped then the solenoids are probably ok. the angle sensor is your problem. this site has some excellent threads on this issue. try looking as far back as two years.