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Old 08-17-2020, 10:21 AM   #1
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ONAN MDJE 7.5 shutdown solenoid problems

On the last run of the gen it started "stuttering" for lack of a better word. Wouldn't hold freq or voltage and quit before I could shut it down. The energize to run fuel control solenoid was getting a fast interruption of power, that was causing the stuttering. It hammered the control linkage and broke the ball joint I'm looking for in my other post this morning.

Now, to my question. The solenoid function makes this engine energize to run. Are the oil and temp auto shutdowns in series with the manual shutdown switch? I'm on the hook for a couple of days without the manual. I patched the ball joint joint with a hose clamp and cleaned up the wire and resecured it. Gen ran fine for about 30 min then started stuttering again. I suspect the issue us "up stream" of the solenoid A general description of the shutdown circuitry would be very helpful in troubleshooting .
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Old 08-17-2020, 01:46 PM   #2
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Could be a loose wire or connection. Manual doesn't have a wiring diagram, but I have these 2 loose pages.

You can download a manual here:
https://greenmountaingenerators.com/...S-974-0750.pdf
Too big to post.
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Onan_Diesel_Controls_612-4792_b.jpg   onan-75-mdje-wiring-diagram-5.jpg  
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Old 08-17-2020, 01:54 PM   #3
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Thank you. That's what I'm expecting to find. Lose, bad or chafed and grounding. I let some knuckleheads work on it last year. Found the solenoid wire chafing on hose clamp tails left too long and zip tied to the fuel injector lines. Won't tell you what they did to the fuel system.
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Old 08-17-2020, 03:52 PM   #4
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Look in the control box. There are some little screws that come loose and they can cause a issue where the solenoid trips. I painted them with toenail polish.
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Old 08-17-2020, 05:42 PM   #5
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Good tip. Thank you. I'll have a look see.
Quote:
Originally Posted by Bigsalmonfish View Post
Look in the control box. There are some little screws that come loose and they can cause a issue where the solenoid trips. I painted them with toenail polish.
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Old 08-18-2020, 05:12 AM   #6
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Look on the head, mine would come loose at the temp sender on the head and cause the same symptoms you described. It’s very hard to tighten the Phillips head so I made a wedge of some sort to secure it
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Old 08-18-2020, 08:18 AM   #7
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Thanks to all for the info and suggestions. I'll dig into it after I get home. We've been on the hook for two nights and the batteries are holding up well as of this morning. So I'll be postponing removal of the sound shield and serious troubleshooting until I get back. The main engine alternator will get a workout as we head back today.
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