EX140US-5のエンジンが切れない件について (Regarding the engine not turning off)

1. #1Old Syko2026-09-20 07:11

   Translated to English Regarding the Hitachi EX140US-5: the engine shut down because the key was turned to the OFF position. When the key is cycled from ON to OFF, the throttle motor moves to the shut-off position; however, since the alternator continues to generate current while the engine is running, it appears the Machine Controller (MC) is failing to detect the key-off signal. I suspect the fault lies with the relay, but since this component isn't listed in the parts catalog and the part number is unknown, I plan to remove and inspect it, then perform an on-site repair using a generic replacement. Is there anything specific I should prepare? Where is this component located? Has anyone here performed a replacement or repair on this part? I would appreciate any advice. Photos or diagrams would be especially helpful.

2. #2digger242j2026-09-20 10:47

   Thank you, Old Syko for providing that translation. To yamasurume, welcome to Heavy Equipment Forums. One of our Forum Rules is that English is the official language of Heavy Equipment Forums. In the future please abide by that rule. Best of luck in finding a solution to your problem.

3. #3Rocky382026-09-20 12:30

   Yep, battery relay stuck closed. Generic 24V will get you going. Good luck

4. #4yamasurume2026-09-20 15:11

   ありがとうございます。日本語で入力したため、翻訳が少しずれてしまったようです。EX140US-5についてです。キーをオフにしてもアクセルモーターが停止側に動かず、エンジンが停止しません。エンジンをかけずにキーをオンオフするとアクセルモーターは停止側に動くので、エンジン作動中はMCがキーオフを認識していないのではないかと思います。考えられるのは、逆流防止ダイオードが破損し、オルタネーターからの電流が図の端子5に逆流しているのではないかということです。しかし、ダイオードは部品リストや配線図に記載されていないため、どこを確認すればよいのか、どのような部品を用意すればよいのか分かりません。フォーラムでシートの後ろのパネルにあると読んだので、明日開けてみようと思いますが、経験のある方からのアドバイスをいただけると大変助かります。

5. #5yamasurume2026-09-20 15:14

   まず、オルタネーターのカップリングを取り外して、エンジンが正常に停止するかどうかを確認したいです。もしダイオードの故障が見つかったら、自分で修理したいと思っています。3Aのダイオードを用意しても大丈夫でしょうか？

6. #6Old Syko2026-09-20 15:17

   yamasurume, you need to do your own translation and post in English as required. Thank you. It seems the translation was slightly off because I originally typed in Japanese; I am referring to the EX140US-5. When I turn the key off, the throttle motor does not move to the stop position, and the engine fails to shut down. However, if I toggle the key on and off without starting the engine, the throttle motor *does* move to the stop position, which leads me to suspect that the MC (Machine Controller) isn't recognizing the key-off signal while the engine is running. One possibility is that a backflow prevention diode has failed, allowing current from the alternator to flow back into terminal 5 (as shown in the diagram). However, since this diode isn't listed in the parts list or wiring diagram, I’m unsure where to check or what replacement part to get. I read on a forum that it might be located in the panel behind the seat, so I plan to open that up tomorrow, but I would greatly appreciate any advice from those with experience.

7. #7Old Syko2026-09-20 15:19

   First, I would like to remove the alternator coupling and check if the engine stops correctly. If I find a faulty diode, I plan to repair it myself. Would it be okay to use a 3A diode?

8. #8digger242j2026-09-20 16:26

   It's actually the first rule: Standard English is the official language of Heavy Equipment Forums, all posts must be made in English. Posts appearing in a language other than English will be removed from the Board.

9. #9yamasurume2026-09-20 17:00

   EX120-5のものですが、姉妹機種なので同じものだと思います。

10. #10yamasurume2026-09-20 18:30

    英語で再投稿しました。これでよろしいでしょうか？

11. #11DDoug2026-09-20 18:44

    .

12. #12Welder Dave2026-09-20 21:33

    Is it possible you could tell him in Japanese he has to use English on the forum? He's just a guy trying to fix his excavator.

13. #13Tones2026-09-20 21:47

    Either way Dave everyone has to use a translater including the OP on this post. The OP has been mentioned by a moderater. Kia kaha.

14. #14yamasurume2026-09-21 05:36

    Yeah, sorry about that

15. #15Old Syko2026-09-21 08:30

    Dave he has access to the translator just as we all do as he has proven with his last post. You also have access to this. Use of the translator gives us all access to more repair info and even parts that are made elsewhere no matter which language you and your provider speak. Do a quick search for the translator and you can use it between multiple different languages but the results aren't always perfect. From the schematics yamasurme posted I would say he is on the right track but I have no experience with his particular machine so someone else needs to pitch in.

16. #16CM19952026-09-21 09:37

    We all have quick and easy access to a translator - that's not the point. HEF is an English speaking forum and ALL posts are required to be in English. The official rule says the posts not in English will be removed. There is leeway being shown here.

17. #17Old Syko2026-09-21 10:30

    I'm well aware of this which is why I posted as I did. Personally I have posted on other foreign sites where I made the the translation to their language and as soon as I posted it was changed back to English. Don't know if that is what took place here or not but it does happen. I've lost access to 2 other sites because of this so yes it can happen. BTW I'm possibly as redneck English as anyone else you know.

18. #18Welder Dave2026-09-21 15:28

    Just trying to help someone out. Looks like it has been resolved.