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Onan Emerald NHE Idle Problem


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  #21  
Old 02-03-2017, 09:47:07 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

Was your reg dead?

To clean my slip rings I ground 2 of the 4 tines off a kitchen fork, and stuck a cut strip of schotchbrite pad on end and tied other end on with cotton string. With engine hot wired I just hold it under the brush holder against the slip rings.

Gen doesn't idle , it runs at 1800 rpm at ALL TIMES, no load all way to full load, otherwise you wouldn't get 60 hz.
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Old 02-04-2017, 09:05:30 AM
Max Thompson Max Thompson is offline
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Default Re: Onan Emerald NHE Idle Problem

Quote:
Originally Posted by Ed III View Post
What makes me nervous is that I have done the same in other applications and it was difficult to hold everything ........... Springs, etc, in place for reassembly.

Sometimes you can use alligator clips on the brush wires to hold them back in the brush holders, assemble then release the clips.
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  #23  
Old 02-04-2017, 10:28:58 AM
Gunny Gunny is offline
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Default Re: Onan Emerald NHE Idle Problem

Failure to idle??????

That generator runs at 1800 rpm all the time. There is no "idle" function.
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  #24  
Old 02-04-2017, 11:51:39 AM
Pete Spaco Pete Spaco is offline
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Default Re: Onan Emerald NHE Idle Problem

I have only had to get into the brush area on my 6.5NHE once to clean the slip rings. I had to do it twice, because, even though the slip rings LOOKED pretty good after the first cleaning, they were not clean enough to pass current well.
But I don't remember any particular problems working in there, except---

I broke off one brush wire. IIRC, those wires are held in place with a TINY pop rivet. I never was able to find pop rivets that small. I guess it wouldn't have helped anyway since I wouldn't have had a small enough rivet tool. I think I replaced that pop rivet with a 4-40 screw and nut.

FWIW, I used a piece of wood, like a doctor's tongue depresser and taped 320 grit wetordry sandpaper to it to do the job. I didn't want to take any chances with metals in that area.

Pete Stanaitis
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  #25  
Old 02-04-2017, 01:04:54 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

At no load rotor excitation voltage is ~ 36 V, manual say it ranges from 18-60 VDC. But can just disconnect the AC reg and rotor will be dead. With no rotor excitation stator only makes ~1-2 VAC. So basically everything in genhead is closed enough to dead with reg unplugged.
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  #26  
Old 02-04-2017, 04:12:51 PM
Jim Marcozzi Jim Marcozzi is offline
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Default Re: Onan Emerald NHE Idle Problem

I've actually set many gen carbs up with the idle mixture closed off (full lean). At 1800 or 3600 RPM, the main jet can do all of the work by itself.
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  #27  
Old 02-04-2017, 05:13:04 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

I've read here that's the case for lawn mower type engines. And my experience on a 10 hp snow blower engine tends to confirm that. Idle jet was almost fully plugged, when I tried to get that engine to run at anything less than a too high rpm it would die. Cleaned out the idle jet and it would run real low rpm, chug ...chug ...chug.

The Stak post I read said Onan's still need the idle jet at no-load.

Guessing they don't make special carbs for constant rpm gens though..... so
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  #28  
Old 02-04-2017, 08:36:16 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Thanks to all who are showing an interest and leaving comments. It all helps. I have an update, but first I will try to respond to questions.

Yes, the regulator was dead. I have not ruled out tearing into it one day to see if it can be repaired and kept as a spare. One leg showed an improper short and another showed an improper open. I can't find a schematic, but that is for another day !! For now, it has been replaced and Generator is working.

Perhaps I did not select the best terminology when I say the engine does not idle, nevertheless, that is what it is. While it is true that when in use, 1800 rpm should be constant, if the engine, with the governor disconnected, will not run at lower rpm, the engine is not running properly. In my case, the engine intolerance to lower rpms causes the engine to run rough at 1800 and shuts off at speeds below.

I took time today to clean up the slip rings and brushes. It was easier than expected since everything, brushes, springs, etc. stayed together rather than having to be held in place. Before I started, the field resistance was in the 60 ohm range and after cleaning it was about 25 ohms. Seems I remember that being within tolerance.

Carb !! Took it off and started looking for those .010 holes. I did find 3 really really small holes back into the carb a little further that the larger .010 hole that was described earlier. They did not appear to be stopped up, but I spent some time making sure they were clear with a very flexible piece of small wire, about number 30. Those holes have access blocked from the outside by one of those pressed in brass balls making it a one way, inside carb job. In fact lots of small passages before cleaning would require removal of those balls to be sure the lines are clear. I depended on the soak to clear those lines, but it just did not do the job. I am not planning to remove any of those balls.

Pictures attached. I spent lots of time snaking wires through small lines in the carb body. That thing looks so simple, but does indeed have lots of little lines in it. I think I counted 10 or so of those little balls blocking ports that I would like to have cleaned. I did find one thing that is interesting. Looking into a little side port on the air cleaner end, looking toward the M and S ports, you can see what appears to be a bolt or screw coming from one of the ports down into the body. I'll bet if that ball were removed, one would see an adjustment. I don't see any build up in there, so I am going to leave it alone.

I do have one thing that is really hopeful. The small port with the jet that sticks down into the bowl enlarged almost double. I had been hesitant to use metal to clean it due to factory warnings. I used a piece of copper wire, about number 22 and very cautiously and gently eased it through the jet. It made a big difference in size.

I still have the carb apart and will reassemble it tomorrow after I am confident that I can do no more. I sure hope this gets it because I am "slap" (southern lingo) out of ideas.

It seems my phone names all photos the same, so I can only post one picture per post without a name change, so, only one photo here.

Ed
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  #29  
Old 02-04-2017, 10:14:16 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

-- Rotor resistance is 20.25-24.75 ohms, so if slip rings are clean your 25 ohms sounds good. I say if clean because high ohms from dirty slip rings can mask a partially shorted $$$$ rotor.

Quote:
Originally Posted by Ed III View Post
--While it is true that when in use, 1800 rpm should be constant, if the engine, with the governor disconnected, will not run at lower rpm, the engine is not running properly. In my case, the engine intolerance to lower rpms causes the engine to run rough at 1800 and shuts off at speeds below.
Mine ran bearly ran and ran VERY VERY rough and only the main jets ( in dip tube) were plugged, idle circuit could be plugged but mine wasn't. However on snow blower plugged idle ports made engine stall out when I tried to run it at low rpm

When I rammed out my plugged .010 idle ports on snow blower carb I removed idle mix adjustment needle valve and reverse flushed the ports to clean out any partials that were freed from ramming. I used compressed air and Liquid carb cleaner can since liquid can remove particals better than air. The .010 inch holes are smaller than any other idle passageway , except for the idle needle valve. So if don't reverse flush to get particals out of carb they likely will plug port up again. The passageways with balls at ends seem to be larger than any of the jets so I don't think it's as important to ram them out. For most carbs I usually just soak carbs in gas and blow out every thing with 150 psi air. I do physically clean the jets I can remove though.

-- Make sure you remove and clean the 2 jet tubes in carb dip casting that hold bowl on. On mine they unscrew and have eight ~.020 inch dia cross holes that were HEAVILY plugged.

Quote:
Originally Posted by Ed III View Post
--- Looking into a little side port on the air cleaner end, looking toward the M and S ports, you can see what appears to be a bolt or screw coming from one of the ports down into the body. I'll bet if that ball were removed, one would see an adjustment.
Think your seeing the air metering jet tubes. On mine under the M& S screw caps were 2 different dia jet tubes, there is no adjustment. They were similar to the 2 longer ones in the carb bowel dip casting. Mine were clean even though the 2 long ones in bowl were heavily plugged.

--- lot of work to fix a voltage reg, potting is a real PITA to remove, problem might be a dead IGBT or cracked bismuth solder that holds the ceramic daughter boards to the main board.

Last edited by len k; 02-04-2017 at 10:51:12 PM.
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  #30  
Old 02-04-2017, 11:10:43 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

I may be out of business unless I can find another of the small jets that goes in the bottom of the bowl. This one snapped off one of the ears that the screwdriver grips.......about half way down !! The only way to get it out was to use a left hand bit and then an extractor. There is no damage to the carb body, but the small jet is toast. I sure hope that is available by itself.

Below shows what is left. 😟 Any thoughts on getting one?

Ed
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  #31  
Old 02-04-2017, 11:23:14 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

For removing rest of it heat the aluminum casting, AL expands ~ twice as fast per deg as brass. Don't want to cook seals so start with a 1500-1800 watt hair drier on high for ~ 5 minutes. Save the propane torch for later more desperate times.

Look in parts manual , see if lists a carb kit with those parts.

Last edited by len k; 02-05-2017 at 02:39:50 AM.
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  #32  
Old 02-05-2017, 12:45:43 AM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

The part came out clean. I just have to locate another jet. I do remember it is not on any breakdown drawing that I have. Going now to look at what was provided earlier in this thread.

No jets in the carb kit that I purchased.

Ed

Just as I remembered. Neither the main jet nor the small jet are shown on the parts breakdown !!

Ed
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  #33  
Old 02-05-2017, 02:43:34 AM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

On mine the 2 long jets by eyeballl looked to be the same, but at the time I didn't really scrutinize them very carefully. Could have machine shop make one, but I'ld ask others to confirm they are the same with a micrometer first.
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  #34  
Old 02-05-2017, 10:20:24 AM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Thanks, not the same on this carb. The large one probably weighs 5 times more than the small. I have a breakdown diagram of the Nikki carb at the shop. I don't think that part is shown, but I will look this afternoon.

After a search on this forum, I think the part number for the idle jet is 146-0451. I can't be sure because they used more than one carb and pictures of the part show no detail.

Looks like 50 bucks plus for that one, if it is available !!

Signing off until I can get a part. Will report back.

Ed
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  #35  
Old 02-05-2017, 01:26:13 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

Should be able to get a whole used carb, here or ebay. I've helped some people that had burnt rotor or stator windings. With burnt windings itis BER so it becomes a parts machine.

Hopefully one of the smarter guys will know if that jet tube is available separately. I just look at the parts manual, have not seen your model or what comes in the repair kts.

Last edited by len k; 02-05-2017 at 02:53:19 PM.
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  #36  
Old 02-05-2017, 07:54:42 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Thank you. I will search here and elsewhere for the idle jet. Perhaps someone has an old carb.

It was in another lifetime, but I have done some motor rewinding. From the little I saw when I cleaned the rings and brushes, I would think those could be rewound, but I didn't look closely.

Ed
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  #37  
Old 03-01-2017, 08:14:19 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

I said I would report back. The idle jet arrived. While waiting, I did some more cleaning of the carb. I installed the new jet, reassembled the carb and reinstalled it. The engine is now running very good at all RPMs. I used my multi tester with a cycle range to set the generator to the proper 60 cycles, plus or minus a little.

It now has a very slight surge/hunt. It's not a big deal, but not proper either. I would like to get it "more" stabilized. I used the manual to set up the governor. Adjusting the main jet on the carb does not seem to affect how the engine runs very much. I suspect the carb may still have some build up. It could be a governor adjustment, but I did follow the manual, except where it called for multiple load adjustments. I used a cube heater to load the unit.

The surge/hunt is so small that I cannot isolate the problem. I cannot tell whether to work on the governor or take the carb off..........again. I really don't think I am overthinking this. I believe it still needs work to get everything as smooth as it is intended to be.

Any thoughts?

Ed
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  #38  
Old 03-02-2017, 09:31:56 AM
Kevin K Kevin K is offline
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Default Re: Onan Emerald NHE Idle Problem

Is it hunting at no load, partial load, full load, or in all cases?

Hunting only at no load is usually a carburetor issue.

If hunting only at partial or full load, check for an air leak in the intake manifold. These manifolds are pressed together with a sealer, and sometimes they leak.

Check the manifold to engine gaskets and carburetor to manifold gasket.

The main jet should be adjusted only under FULL load. Add enough heaters to bring the set to full load, and adjust the main jet for minimum throttle opening.

The "idle" jet should be adjusted only at no load. Back off the throttle stop screw and hold the governor rod against the screw to get about 55Hz on your frequency meter. Adjust the "idle" jet for highest engine speed. Be sure to reset the throttle stop screw after you are finished.
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  #39  
Old 03-02-2017, 01:28:41 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Quote:
Originally Posted by Kevin K View Post
Is it hunting at no load, partial load, full load, or in all cases?

Hunting only at no load is usually a carburetor issue.

If hunting only at partial or full load, check for an air leak in the intake manifold. These manifolds are pressed together with a sealer, and sometimes they leak.

Check the manifold to engine gaskets and carburetor to manifold gasket.

The main jet should be adjusted only under FULL load. Add enough heaters to bring the set to full load, and adjust the main jet for minimum throttle opening.

The "idle" jet should be adjusted only at no load. Back off the throttle stop screw and hold the governor rod against the screw to get about 55Hz on your frequency meter. Adjust the "idle" jet for highest engine speed. Be sure to reset the throttle stop screw after you are finished.
I'll have to check to find out if load makes a difference with the hunting. I just didn't know to look for that. I'll spray something around the manifold too see if anything changes. I did that earlier, but it had so many problems at that time, it probably would not have shown up.

I did not know about adjusting the carb under load/no load conditions. Good information. I will try that. It will be a couple of days before I get back the shop. Thanks !!

Ed
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Old 03-04-2017, 06:16:22 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Okay, had an opportunity to make some adjustments and run some tests.

I was able to adjust the idle jet to where the unit ran perfectly with no load. I was unable to get it loaded to the full 6500 watts. I was able to get about 4000 and it did surge under load. It was not bad, but I would not use it that way. The main jet adjustment did not fix the problem. A picture is attached of my multitester showing an average cps reading without load.

I decided it was time to check for a vacuum leak. I usually use smoke, but just too much airflow around the air cooled engine to learn anything. I used WD40 thinking if there was a leak, I would hear a difference when the fluid went into the area of the leak. There was no change. I sprayed all around the carb to manifold, manifold to cylinders and the sealed joint in the manifold. Is there a better way to check for a vacuum leak?

Finding no vacuum leak, I removed the carb (4th time), disassembled it and it is now in the gunk carb cleaner soak tank. Instructions say 20 minutes. Last time it stayed in for 40 minutes and it didn't do much. This time it is staying for 4 hours. I don't think much of this cleaner.

I will reassemble tomorrow. Any thoughts or advice at this point??

Thanks,

Ed
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