I've got a Case 580K that recently developed a problem that it won't shut off when I turn the key off. All the accessories will turn off, lights, radios, etc. And the alternator light illuminates. But the engine doesn't stop running. I have to manually trip the fuel pump shut off lever to get it to stop running. So first thing I did, I changed the ignition switch. Same result. Then I changed the alternator. Nothing changed. Some things to note, when this issue first started, it was just slow to shut off. Meaning, I would turn the key to the off position, and after a couple seconds, the engine would finally turn off. It started to go longer and longer, to the point it is now that it will not shut off at all. A couple months ago, I had to change the fuel shutoff solenoid, so I thought that might be suspect. But with the key off, and the engine still running, if I disconnect the fuel shutoff solenoid, the engine will shut off. So there is still 12v at the solenoid with the key off. In researching this, I've read that when the key is turned on initially, through the ignition switch, the battery excites the alternator to start charging. This works fine for me as I have no problem with the system charging. But when the key is turned off, the exciter wire should be grounded and the machine will shut off. It doesn't seem like this is happening. It seems like the alternator is backfeeding the exciter wire when the key is off, keeping the fuel solenoid energized, the alternator light on, and the engine running. If I take a jumper wire and jump the exciter wire post on the back of the alternator to ground, with the key off, the engine will shut off. Any ideas what could be causing this?
Replace the fuel shutoff solenoid on injection pump. It's on the bottom of pump and takes a thin 15/16" wrench to remove solenoid. Of course you need to check and make sure you are loosing voltage at solenoid when you turn key off.
Thanks for the suggestion. The solenoid is new about 3 months before this started happening. I ordered a spare, so I will change it out just to be sure. But I do believe that it's working as it should. With the key on there is 12v at the solenoid and the tractor starts and runs fine. The problem is when I turn the key off, the solenoid stays energized with 12v and stays running. If I then disconnect the solenoid, it will shut off. So seems like it is functioning correctly, but I will swap solenoid with another new one just to be sure. Thanks.
Could it be the relay ?
You need a diode in the excited wire so power goes in to charge the feild but not backfeed to the pump solonoid. Once the alternator has been excited it will stay that way until the engine is shut down. So to test this disconnect the Exciter wire and crank the engine, now just touch the exciter wire to the post or terminal to activate charge. leave wire unhooked and engine should shut down with key switch. Careful not to let loose exciter wire short to ground
I don't see a relay in the electrical diagram. Any idea where the physical relay is on the machine? This makes sense to me about putting a diode in the exciter wire, and I believe other applications have a diode. But as mentioned above about the relay, no diode is shown in the wiring diagram. Any idea if there is one on the actual machine and where it is located? If there actually is one on the machine, then it could be bad allowing electricity to backfeed and keep the machine running. And I could replace it. If I knew where it was....
Sense you are keeping your 12v after key is turned off and engine dies when you unplug solenoid then there is no need to replace it. You have an issue in your wiring harness, somewhere your wire for your solenoid has shorted to constant hot wire and keeping voltage at all times. So check your harness for bad spots, I'd start at key switch area and work down from there.
In my experience, it is rare for a hot wire to "short" to another hot wire. But I will check that. If that were true, I should have 12V constantly at the solenoid. I'm reading more up on this, as I've never been very up on electrical theory, and I'm gaining a better understanding of this alternator system. And by looking at the electrical schematics, it all is coming together. So the way Case designed the system is when the key is turned on, 12V power is fed from the battery to the ignition terminal on the key switch. The exciter wire is connected to this terminal and feeds 12V to the small post on the back of the alternator. This 12V signals the alternator to start charging as soon as the engine is started to power all the accessories. Once is starts charging, the exciter wire is basically supplied with 12V from the alternator. This is evident because the alternator light on the console is not illuminated. If the alternator stops charging, the exciter wire become a ground for and the alternator light is illuminated. When the key is switched off, no power is coming from the ignition terminal into the exciter wire. The alternator bulb is supposed to be enough of a drain to bleed off the voltage in the wire and shut the system down. But that isn't happening anymore in my backhoe. Honestly, the more I read up on it, the more I don't think anything is really "wrong" other than getting older. I will check the things mentioned above. But at the end of the day, I think I'll just be adding a diode to the exciter wire. I was just worried that the diode was a coverup for something else wrong. My machine doesn't have a lot of hours and I didn't want to make a hack fix. But now that I better understand the system, I don't see it that way. Thanks for the help guys. And I will update when I figure out what works.
I do not any service information on your case. I did however look at the parts break down and it shows to have a diode in the engine harness and one behind the dash panel it does not specify function of diode in the parts book. The diodes look like a two wire plug that is just blocked off. Case construction parts look up is where I saw this under electrical. The diodes are listed as such . I don't know how to do a link. So I feel it has factory diode. It hashas fai internally and is letting current travel both ways. Another way I resolved this issue temporarily is to put a toggle switch in Exciter wire turn it on to excite alternator then turn it off and engine will shut down from key switch, kinda a pain thus temporary.
In case parts book 580k . Doide part# L71879 line 4-018 engine electric circuit shows one diode. 4-028 side console wiring harness connections shows three diodes all with the same part number.
Thanks for digging into it from your end. I just looked up the parts diagrams that you mention. Here is what I found. The diode you are talking about is item #6. So I will have to look in the console and see if I can find those diodes and maybe test them. Thanks again!
I don't know if this helps. From the service manual.
Hello, I seem to have the same problem with my 580K. It will not shut off unless I disconnect the shut off solenoid or disconnect the feed wire at the alternator. It is backfeeding into the harness from the alternator light wire. Just curious what you found to fix your machine? Thanks in advance.
Welcome to HEF, WaJH ! Unfortunately Zef_66 did not come back and let us know if he ever figured out his problem. Sadly that happens way to often. Zef never verified that it was getting a voltage from a defective diode. Do as Coy suggested and start your own thread.
I had to do this on my machine for this exact reason