Hi Friends! I recently picked up a mid 90s vintage, Hitachi EX120-2. Super tight and well kept, but has a few issues. The biggest one at the moment is the throttle and kill servo. Throttle buttons illuminate and change with the buttons pressed, but motor doesn’t respond to input. I haven’t checked any voltages yet, only checked fuses and all are good. I was told you have to relearn the throttle after the motor is changed? I think it has been since I found another in the tool box up front. What’s the relearn process? Heard about a switch in the back somewhere, but can’t seem to locate it. And when the key is then turned off, the engine doesn’t stop, have to manually pull the cable to kill. Wonder if it’s related. Curious to hear what the gurus say, want to get this issue resolved before I dig into anything else.
Welcome to HEF Will . The machine serial # prefix is 12N ? See screenshot below for learn procedure.
I'm just here to observe.... bought one of these machines last month and I have a few gremlins I'm going to tackle. Like to see how it goes for you Will.
Great! I appreciate it! Yes, 12N-***** is the serial. I’ll give it a shot and see! No switch on these models then?
Nope
Well I gave it a shot to no avail. Might try and swap the other motor I have. Wiring all looks good in the pump cabinet, so I don’t think that’s the issues.
See EC motor test specs screenshot below. Do you have a service manual ?
Is that on rhe motor side of the plug, or the machine side? I do have a copied manual in a big binder. It’s. Out of order and a pain to use. There a good PDF available?
Motor side . . LACHAU posted a link to an EX120-2 service manual in thread below,see post #9. HeavyEquipmentForums
Thanks again Diesel Dave! Ill look over that while im on a plane tomorrow. Wont be back in town til Sunday. Hopefully be able to make some headway next week on the old beast!
Had some time today to mess with it, ohmed out the stepper and it came back right in spec. Noticed next to it it had another sensor with 3 wires that must read throttle position!? Tried to ohm that out too but couldn’t get anything from any combination of pins.
The EC sensor specs below.
Check if the EC (engine controller) and PVC (pump valve controller) below the plastics behind the operator seat are powered up with key on. The red LED on each controller should be flashing approx once per second.
and check cable adjusted to get min and max travel
Have an update on the problem. I found a local guy who is a guru for these older machines, has access to the diag software, as well as the cable to plug into the machine. He was able to hook me up with a computer, the MP DR. software, as well as the cable. Plugged into machine and it posted Fault Code 4, which is a failure of the EC (engine controller) Sent a picture of the scan over to my guy, an he say he’s seen it a bunch of times on these, I guess due to voltage spikes from the alternator. Would you chance it with one from eBay, find someone to rebuild it, or source an OEM one!? I don’t mind spending money if I’m going to get good stuff
More good news! My guy had an aftermarket “EC” from another machine he gave me to try. In the meantime he came up with a NOS Hitachi EC, and PVC. Kinda pricey, but oh well. Plugged in the new controller and voilà, the engine starts up, an all the rpm buttons work, auto idle works, cold temp button works, it’s all works! Only issue I’m still having related to that system is the stop motor: The low stop on the pump was set to idle speed, so it would never kill the engine. After some digging and watching the actuator while someone else turns the key confirms the pump goes into “start” when the key is turned on, and then destrokes when the machine is shut off, killing the fuel from the throttle lever, not the actual kill lever. Reading into the stop motor and emergency relay, thinking something related to that system is fouled up. Currently the cable is disconnected from the beaker for the stop motor, and I can’t seem to make it do anything electrically. So my questions would be: (1) any issues with leaving that circuit unhooked, only real risk would be if something happened and the throttle stuck I couldn’t shut it off, or it loses oil pressure and I didn’t know it. (2) what is the correct procedure for setting all the throttle actuators and cables and such? Dug through the book for a bit and could find the rpm readings, but not a procedure for adjusting the hard parts of the system. Making lots of headway, excited to get this beast out moving dirt again
The stop motor system needs to see a key off cycle. There is diode “D3“ in the power on circuit which could affect that. Check if there is power at fuse #5 with the key OFF. If there is power it is likely a bad D3 diode. Diode 3 is connected to a red wire with white markings and to a red wire with black markings, near the Dr. EX connection terminal.
@Diesel Dave im leaning on your for this next one. Still have poor hydraulic operation, wants to stall engine if you do too many things at once, or go too fast. No codes other than code 34 & 36 which are included. I’m stumped on where to go next. View attachment IMG_9578.jpeg
I assume you have an aftermarket “generic“ PVC or an OEM PVC for a -3 machine. Codes 34 and 36 are only legit on -3 machines as the -2‘s don’t have the (2) related sensors. Ignore those 2 codes. Using MPDr live data, - what’s the “actual engine speed“ when in “P” ? - with pilot controls in neutral, what is the “pump displacement angle“ ? - with pilot controls in neutral and throttle in P , what is the “differential pressure“ ?
Forgot to add , - with pilot controls in neutral and throttle in P , what is the “pump delivery pressure“ ?