My first thread or forum post ever. I have a Hitachi 1991 EX120-2 and recently have had a problem with the hydraulics etc. I have replaced the outside wiring harness, both displacement solenoid valves the PVC and EC and now I am looking at the angle (A) sensor. In one of the tests, the tech manual that I have says I should compare the pump swash angle and the pump swash angle sensor using Dr.EX which i have done. the pump swash shows 239 degrees and the pump swash angle sensor shows 50 degrees. The section of the book on how the pump angle works says the minimum angle is 2 deg and the max is 24 deg. Im thinking that both readings should be the same and should be between 2 and 24, but I cant find anything more in the books I have. Does anyone have the answer for me? Thanks in advance
I believe the “pump displacement angle“ and “pump displacement angle control signal“ may match only when the hydraulics are being operated. . Monitor the “pump displacement angle“ with controls in neutral and again when using multiple hydraulic functions. Specs in screenshot below.
Thanks Diesel Dave, I will try that this morning.
I see on another post you bought DrEx from China. Do you have a link or supplier contact info ?
This is his email address. [email protected] I got the Dr.EX from him on Amazon, but since we have been talking a lot and I have bought several parts from him.
I have an error to correct! The numbers 239 and 50 have a very faint decimal. When I cleaned my glasses I see 23.9 and 5.0. These numbers make more sense. I did a bunch of testing and I have found the engine speed sensor not to speck. All the voltages at different speeds are reading high. The angle sensor is out too. It was set at .62V and it sould be 4.40 +/- 0.03. I moved the sensor from stop to stop and got .07 as a low and 1.11 as a high.
Did you unplug the 2 solenoids on top of the pump before trying to adjust the angle sensor output voltage ?
Yes I did. Did you contact the guy with the Dr.Ex.
What are the Dr.Ex engine RPM readings. Rpm specs in screenshot below.
With the assumption that the hydraulic pump is at max displacement and your actual angle sensor output voltage readings are much lower than spec I suspect the dot on the sensor shaft is not oriented properly. See screenshot below.
Hey Diesel Dave, I’m just working my way to getting RPM’s. I know what you are saying with regards to the A sensor and the dot, but the thing is that I have had this machine since the mid 90’s and have never touched the A sensor. It may have differed a shock just before I replaced my wire harness. The harness was in bad shape with lots of insulation cracking etc. I was on a job in June and it started acting up on me and that’s when I believe the pump went to full swash angle. I got the machine back to the shop and started the whole process of changing the wiring harness and checking all the sensors. I found the displacement solenoid valve closest to the suction. End of the pump had failed on me so I replaced it. Unfortunately, that wasn’t the end of the problem and that’s where I find myself now.
Just as a follow up on my repair job I have five or six different books that I’m gathering information from two of them are for the John Deere 490 E one is the repair Manuel. The other one is operations in a test, then I have some Hitachi manuals. The bottom pages are starting with a T the other Hitachi manual has W for the page numbers and then I’ve got a small booklet from the technical training centre for Hitachi. Unfortunately, in this, I’m finding some conflicting information and I’ve seen some fairly serious typos in the John Deere manual specifically. As an example in the operations and test manual, I’ll show you screenshots of two different pages in the same manual to do with the EC sensor and testing the voltage. This kind of stuff is driving me crazy. And of course, being dyslexic doesn’t help anything at all.
If you are 100% sure the hydraulic pump is in max displacement, the sensor shaft is oriented correctly and the angle sensor output voltage is only approx 1.00 volt , then it stands to reason the angle sensor is bad. . What exactly is the major issue(s) with the machine ?
I hear what your saying about the various manual’s frustration. It’s bad ! I am currently working with another HEF member with his EX120-2 . I first look at the EX120-2 manual, if the description details are poor I refer to a EX120-3 manual. I find the Deere 490E manual best when needing accurate wiring harness details.
The EC sensor output voltage at low idle and high idle speeds from the EX120-2 manual below I feel are accurate.
So the rpm’s are this. I is 560 L is 990 E is 1376 P is 2192. The engine is putting out a fair bit of black smoke, especially at P. I also took voltage from the EC sensor at the different speeds. Very different from yesterday. I’ll put them in order of speed position, yesterday reading, today reading. I 2.5 2.52 L 2.62 2.177 E 3.26 1.815 P 4.14 .815 It’s going backwards from what it should.
Are you getting the EC sensor and the Angle sensor output voltage from Dr.Ex ?
No. Volt meter.
Using DrEX, What’s the EC angle voltage at I L E P ?
Hey Diesel Dave, I wrote an answer to your earlier question but i guess i didnt post it. I was on a job and at one point the machine kind of shuttered. I had a 10' beam in the bucket teeth and i was grading. It went away so I dint think too much of it after that. A day or so later I was running the machine and all of a sudden it was dificult to operate, Wanting to stall, especially when I would try to swing. I got the job finished and got back into my shop and decide to change the wiring harness and check everthing else out. I found the displacment soleniod valve furthest from the engine was bad so I got two new ones of them. now I jusr keep chasing ghosts.
I'm new to the Dr Ex world and haven't looked at that. Im kind of burn out for the day, so I'll check that out in the morning. I did a check on the DP and its very high. Should be about .4 and I have 4.4. When I went to move the machin back into the shop it moved ok but I tred to swing it and it wouldnt move either way. I shut off the pilot valve and shut the machine down, then started it up and all was fine. at that point it was time to walk away.
So currently the engine wants to stall when you dead head any hydraulic function ?
Yes
When checking the hydraulic pump angle sensor output voltage , you are backprobing terminals #2 and #3 ? See screenshot below.
You got me energized so I’m back on the machine. With dr ex I is 2.6 L is 3.24 E is 3.9 and P is 4.6
Whats the Dr.Ex showing for ” actual “ engine rpm ?
I 2.6 and 560rpm L 3.26 and 1216 E 3.9 and 1712 P 4.6 and 2192/2208 bouncing
So I just looked at you picture of the test harness you have and I’ll show you the one I used yo build mine. I’m dyslexic, but this is backwards yo my backwards.
So I know what I’m doing first tomorrow.
One more thing to do before we stop for tonight. Do the engine speed learning procedure in screenshot below . After procedure check to see if the engine speeds increase closer to spec.
I do that reset each time after disconnecting the battery. Twice today already.
May have to do the EC motor adjustment, will save that for another day. Focus on the angle sensor voltage tomorrow.
I cant remember if we talked about the engine speed sensor. I tested tha and those numbers are way out too. I = 2.5, L = 3.183, E = 3.677 and P = 4.105. Tomorrow I will change the test harness and check pump angle, DP and EC sensor again.
Sounds good. I’ll get accurate number tomorrow and then give you a call. Thanks so much.
This is the “N” speed sensor AC voltage taken at the sensor ?
YES ac IS CORRECT.
Those “N“ sensor AC voltage #‘s look very similar to a recently tested new sensor. I would say the engine speed is fairly accurate. I think an EC motor lever adjustment would bring the low idle speed up closer to spec.
I do have a new ECU coming from China. I already did the PVC. when I connect DrEx it tells me it can’t connect or something like that.
I will note that when the displacement solenoids are unplugged it idles a bit faster and doesn’t sound under load.
Sounds like the pump displacement solenoid furthest from the engine is stuck open and setting the hydraulic pump to minimum displacement when the 2 pump displacement solenoids are unplugged. Under normal circumstances, when the 2 (normally closed) pump solenoids are unplugged, minimal solenoid internal leakage and gravity allows the pump barrel assembly to drift on a downward angle to the maximum displacement stop.
I was thinking the same thing a while back, also considering that maybe the harness to the solenoides was backwards, there have been conflicts in my book. I ran DrEx and see that it was telling the system to lower the angle. Everything I could find tells me sol 1 is closest to the engine.
I agree solenoid #1 is closest to the engine. A few months back @mg2361 posted this very helpful wiring harness wire colour layout for the 2 pump solenoids on another EX120-2 thread. . With the 2 pump solenoids unplugged and as you described “engine does not appear to be loaded“ what’s the DrEx actual engine speed in ILEP ? I think that will help determine if rpm is out of spec and how far.
OK i have done similar by taking the pages from my ops and test manual and blowing them up, sticking together and laminating them. not the greatest picture but youll get the idea.
Hi Dave, just wanted to say thanks again for all your help. Here is the manual I was talking about
@Chiefdug Check your messages.
THanks for the great information. There are a few thing more for me to check.
@Chiefdug , this is the Components parts catalog I was talking about . .
Hey DD, that is the one I have. No pump pressure sensor listed in mine that I can find.
Pressure sensor is Item # 67 in screenshot below.
Interesting! mine has the same cover but not this type of content.
If your parts catalog only shows this view of the hydraulic pump as in screenshot below then you don’t have a “Components Parts“ catalog.
Yes you are correct, mine does not have the components.
Well I have had a ton of help from @Diesel Dave and @mg2361 , but still no resolution. I have done lots of test and I’ll post them here to see if anything jumps out at anyone.
And a couple more
We have success! On recomendation from Diesel Dave, I reached out to mg2361 for help. After lots of vigourous testing, retesting etc. etc. we found a bad pump proportional solenoid. I'll back up a bit. I was on a job running the machine and all was fine. One morning I was grading with a 10' steel beam on the teeth/thumb. All of a sudden the machine started to chatter or vibrate for about 3-5 seconds, then went back to normal. It did not do this again. Two days later, all of a sudden operating the machine was very different. The machine wanted to stall a lot, especially at end of stroke on any cylinder and swinging would start with a bang. I checked the machine over as best as I could on the job and found nothing obvious, so I continued because I had about 1/2 a day left loading brush bins to finish the job. Running the machine was entirly different, it looked and sounded like it was my first day (Ive been running this machine for 25 years). I found that it was a bit smoother if I had two cylinders activated before I would start to swing. Anways, I got the machine back to the shop and started to go over everthing. Redoing the wire harness has been on my mind for a while, so I figured now is the time. After lots of testing I found that solenoid #2 (lower pump angle) was defective. The ohms reading was imtermittent from 15.5 ohms to open circuit. During the testing I also found that my fuse box had a lot of corrosion in the fuse plugs. Fuse number 1 was the worst and when I went to clean the contacts they broke off very easily. I looked at getting a new fuse box, but it only comes with the complete cab wire harness, about $1500 Canadian. After lots of searching online I saw individual fuse boxes for Komatsu machines that looked like I could make it work. I got one of them on ebay from China for $60. When it arrived Ilooked it over very carefully and found that the plastic box itself was identical, just the supply wiring was diferent. (several circuits fed from one supply on the Hitachi) so I ended up buying a second one so I could make the supply lines Identical to what I had. On Amazon I found a good price (in my budget) for a Dr. Ex. Reading the reviews I saw that there were a lot of issues with downloading and installing the software, so I decided to get the Dr.Ex with a tablet, installed and ready to go. After buying the Dr.Ex I connected with the guy on Wechat and I bought several items from him, PVC, EC, Pressure switch, Engine speed sensor, Proportional solenoids etc. I also stubmled around on the web and found a guy who does nothing but wire harnesses. I originally reached out to him to get a set of all the plug ends so I could make up some test plugs. Eventually I decided to get the complete wire harness (not for the cab) and would use the plugs from my old harness to make my test plugs. When I got the two new pump solenoids I replaced both of them, tossed the bad one and kept the original one for a spare. I installed the complete wire harness, new solnoids, new PVC and EC etc. and fired the machine up. Disappointed, I had the same problem. That is when I came to this forum and started this thread. (end of August) After lots of back ond forth with DD we found that the pump was in full angle. DD gave me some info and one of the tests was it unplug Solenoid #2 and give it 12 volts. This brought the pump angle down. After tons of reading and wiring checks we found that I had the plugs crossed for the two solenoids. Being quite a perfectionist I could not figure out how I could make such a bad mistake. It turns out that I didn't (reputation saved) It is actually some of the wiring diagrams in the books I was using have it backwards. The books I have are John deere 490E and Hitachi EX120-2. Several spots say soleniod 1 wire 2 goes to PVC pin 111. and Solenoid 2 wire 2 goes to PVC pin 103. THIS IS WRONG THE CORRECT WIRING IS: SOLENOID #1 (closest to engie) WIRE 2 GOES TO PIN 103 AT PVC SOLENOID #2 (furthest from engine) WIRE 2 GOES TO PIN 111 AT PVC. There are a lot of errors in both of these books and several pieces of conflictuing information within the same book. A few more tests with the guidance from mg2361 and DD we found the pump angle was going down, but very slowly (about 20 seconds to go from 22.5 to 6.3 degrees). I changed solenoid # 2 and put my old good one on and the PROBLEM IS SOLVED. What are the odds that you take off a bad solenoid, you buy two new ones and have one bad out of the two you bought, then you put the bad one on the spot that you took a bad one off? At the end of this post I will share two videos, one of the slow angle decent and one of it working the way it should. Now that I am back up and running, I want to thank both mg2361 and Diesel Dave for their patience and perseverance, you have truly been a huge help to me. Hopefully I can pay it forward on here. I have learned a lot of information about my machine and knowledge is power. Video of slow proportional solenoid valve video of proportional valve working properly
Further to the Chiefdug quote above, Referenced in the Hitachi EX1xx-2 or -3 electrical schematics, the ”UP” solenoid which increases pump displacement is closest to the engine and the “DOWN” solenoid which decreases pump displacement is furthest from the engine.
Great story to help others and yourself. Faulty manuals are common. Glad you got it figured out. Simon C
Good deal. These guys are the best. Can you post a link to the Dr. Ex you bought. I’d like to have one for my 120-3.
Sorry about the delay, That is the only draw back that I have found when dealing with China, Our day (Vancouver Island Canada) is their night. Here is the link to purchase the Dr.Ex. https://www.amazon.com/dp/B0BM5QRB7H I bought it loaded on the tablet reaady to go, partially because of the note at the bottom of his Amazon page, " Attention: If you find any malfunction or other software technical issues during the use of diagnostic tools, please contact me for remote resolution. Thank you for your cooperation." I also did not have a tablet. If you do need assistance you can contact him on his WhatsApp. Just scan the pictuer below. He also sells parts at very resonable prices, all you need to do is ask him if he sells it.
Thanks for the link. I’ll order it and post an update when it gets here.
Sounds good. When you get it you will find that the tablet is bigger than the little black case. I bought this for mine https://a.co/d/cHUEgqN It works pretty good. It covers the charging plug hole and part of the on off button, but its pretty good protection.