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Onan Emerald NHE Idle Problem


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  #1  
Old 02-02-2017, 10:43:00 PM
Ed III Ed III is offline
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Default Onan Emerald NHE Idle Problem

Hello, I am brand new to the forum. I found you folks while searching for a solution to my Onan generator problem. I am a regular on the Mercedes SLK forum and the Antique Radio Forum. I restore antique radios and tvs and I enjoy old cars.

Did a search here and learned a lot, but no solution.

At the onset of generator problems, I had no knowledge concerning the Onan. It was just another appliance. The power plant started surging, so I hired someone to repair it. I noticed after repair that I was getting 130 volts instead of 120. Well, in hindsight, it appears to stop the surging, he upped the rpm, which of course upped the cps as well as the voltage. As luck would have it, a tree fell across my motor home, destroying the motor home. It was then I decided to remove the generator and replace my 3000 watt unit at home with the Onan 6500 watt.

That turned out to be a bigger deal than I expected. I built a frame with wheels in wheelbarrow fashion to mount it on. After I got it mounted, I learned the voltage regulator was burned out, probably from the excessive rpm. So, I picked up another regulator and got the engine running again, but the original problem had never been fixed. That, at the time, did not sound like a big deal. Just a tune up, right ???

Description: Onan Emerald III, 6:5NHEFA26100D, Serial I880158541. It is 6.5 k gasoline with Nikki carb, 146 0456. (Nikki number 622028-041). It was made in approximately 1988.

What I did was install new points, properly gapped, new plugs properly gapped, new capacitor. Checked and problem was unchanged. So, I obtained a carb kit, did the carb soak, blew it out and rebuilt the carb.......still no change......?? Then I checked compression. It was 120 and 120. I could not check fuel pump pressure, so I disconnected the line and found lots of flow. Finding nothing wrong, I tried another pump just to be sure.......no change. I removed the intake manifold and checked hoses, etc for vacuum leaks. Nothing found. The choke is on when cold and off when warmed up. I checked spark plug wires by substitution, no change. I am testing with the air filter off of the unit. The governor appears to be working as intended and only gives extra throttle when the engine rpm starts dropping.

The best description I can give is that the engine will not run at low rpm. I disconnected the governor and tried to operate the speed manually. At the required rpm, the engine runs rough and begins reducing rpm until it shuts off. It does not run smooth at higher rpm, but it is fairly stable. Of course at those rpms, the generator output is incorrect. I am using a multi tester with Hz capability to check cycle output, hence engine speed.

This sounds to me like the idle section of the carb, but I have had it apart twice and can't identify the problem. I can squirt wd40 through all of the ports, but there are small lines that could be in there.......somewhere and plugged. Under normal conditions, I would replace the carb, but those I have seen are $250 or more and cost prohibitive !!

Anyone have any thoughts on how to proceed? I will try to post some pictures if needed.

Thanks,

Ed
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Old 02-02-2017, 10:55:22 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Pictures before carb clean up.
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Old 02-02-2017, 10:58:12 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

High voltage 130 vs 120 ...... ????? you have an electronic AC votlage reg, this should not have happened.
Get a killawatt meter and adjust gov to ~ 61-62 hz at no load, maybe 59-58 at full load.

Dead AC voltage reg..... Slip rings get dirty if gen sits for many months. Need to clean them with shotchbrite pad before making AC if gen sits, or reg can die.

Surging .....Mine surged badly and died untill I cleaned carb. I'ld take carb apart and clean it again. Remove carb bowel, remove and clean the TWO jet tubes in carb bowel dip tube casting. One tube is hiding behind a screw in disk.
Also there are 3-4 tiny .010 inch diameter idle ports in carb throat on engine side of throttle butterfly. Try removing idle mix adjustment needle valve and back flush from the .010 inch throat idle ports. After removing idle adjustment needle valve, carb cleaner blown in the hole helps you see if those 3-4 throat idle ports are free.

Manual numbers and link to them.
BGE spec f-k---NHE-spec e-k--EMERALD PLUS--SERVICE--(9-94)--- 965-0528.pdf
NHE-NHEL spec d-p ENERALD III---PARTS ---940-0228b.pdf
BGE spec F---NHE spec D---SCHEMATIC----611-1180.pdf
http://www.twinslan.net/~n0nas/manuals/onan/
Control F to search

Last edited by len k; 02-02-2017 at 11:10:42 PM.
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Old 02-02-2017, 11:19:32 PM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Quote:
Originally Posted by len k View Post
High voltage 130 vs 120 ...... ????? you have an electronic AC votlage reg, this should not have happened.
Get a killawatt meter and adjust gov to ~ 61-62 hz at no load.

Dead AC voltage reg..... Slip rings get dirty if gen sits for many months. Need to clean them with shotchbrite pad before making AC if gen sits, or reg can die.

Surging ..... I'ld take carb apart and clean it again. Remove carb bowel, remove and clean the TWO jet tubes in carb bowel dip tube casting. One tube is hiding behind a screw in disk.
Also there are 3-4 tiny .010 inch diameter idle ports in carb throat on engine side of throttle butterfly. Try removing idle mic adjustment needle valve and back flush from the .010 inch throat idle ports. After removing idle adjument needle valve, carb cleaner blown in the hole helps you see if those 3-4 throat idle ports are free.

Manual numbers and link to them.
BGE spec F---NHE spec D---SCHEMATIC----611-1180.pdf
NHE-NHEL spec d-p ENERALD III---PARTS ---940-0228b.pdf
http://www.twinslan.net/~n0nas/manuals/onan/
Thank you. The rpm will adjust as you suggest, but the engine will not continue to run at that rpm.

Yep, looks like I need to polish the slip rings. Will try to get that tomorrow.

Carb coming back off tomorrow. I removed the large and small jets that project down into the bowl. I could see light through both.

Now you may have hit on something with the .010 holes. I only saw one. I will be checking in there in particular. That could be the problem. I used a carb dip type cleaner that comes in a gallon can with a basket. I left it twice as long as directed, but it did not seem to clean things as well as I expected.

I think I have the manuals. I will check to see if there is anything new.

Thanks again.

Ed
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Old 02-02-2017, 11:22:18 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

For cleaning carbs a physical cleaning beats any chemical cleaning.
On an old snow blower I had plugged idle ports , I used a steel pin that dress shirts come with to ram out the ports.
https://www.smokstak.com/forum/showthread.php?t=140641
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Old 02-03-2017, 02:16:04 AM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

On mine the 2 TWO jet tubes in carb bowel dip tube casting were heavily plugged.
Engine surged and barely ran, had to really play with throttle to barely keep it running.
On my gen (similar NHM) I didn't need to clean the idle ports or the 2 air metering jets on top

Last edited by len k; 02-03-2017 at 12:16:16 PM. Reason: spelling.... mt/my
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Old 02-03-2017, 03:14:53 AM
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Motorhead Motorhead is offline
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Default Re: Onan Emerald NHE Idle Problem

EdIII, Did you ever try to adjust the main jet screw on the bottom of the carburetor bowl?
I can say from many years of rebuilding carburetors that what len k said about mechanically cleaning the jets might be necessary. The specifically sized bores in the brass jets can get build up in the bores that physically closes the bore size to a smaller bore size. This allows LESS fuel to be metered through the bores and thus the engine runs lean. BUT, you have to be very careful when cleaning the jet bores so you don't open up the bores LARGER than they were originally sized. I clean the bores with a piece of stainless safety wire and I also have a few sets of metric and decimal micro sized pin drills.
The jet bores usually clog with solids from moisture in the fuel. You can remove the brass jets and soak them in household vinegar for 3-8 hours.
I have also soaked the aluminum carburetor body in vinegar to remove calcium build up in passages.
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Old 02-03-2017, 10:28:46 AM
Ed III Ed III is offline
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Default Re: Onan Emerald NHE Idle Problem

Quote:
Originally Posted by Motorhead View Post
EdIII, Did you ever try to adjust the main jet screw on the bottom of the carburetor bowl?
I can say from many years of rebuilding carburetors that what len k said about mechanically cleaning the jets might be necessary. The specifically sized bores in the brass jets can get build up in the bores that physically closes the bore size to a smaller bore size. This allows LESS fuel to be metered through the bores and thus the engine runs lean. BUT, you have to be very careful when cleaning the jet bores so you don't open up the bores LARGER than they were originally sized. I clean the bores with a piece of stainless safety wire and I also have a few sets of metric and decimal micro sized pin drills.
The jet bores usually clog with solids from moisture in the fuel. You can remove the brass jets and soak them in household vinegar for 3-8 hours.
I have also soaked the aluminum carburetor body in vinegar to remove calcium build up in passages.
Concerning adjustments, yes, I did work on adjustments, starting with the factory recommended 1 1/4 turn for the main and 1 turn for the idle.

I removed the large and small jets in the bottom of the bowl area. The small one was stopped up. When I finished, I could see light through both, but they could have a coating making them smaller than factory spec. I was quite cautious due to factory literature warnings. I will check those again.

I know for sure there is only one of the ports described as .010 open. I did not see anymore, so I need to look more closely at that. I am disappointed at the commercial carb cleaner/soak. It did not do a good job.

My generator is in an out building and it is cold and rainy today. I will wait for better weather to proceed, but I will report back on my findings.

If anyone knows, is there anywhere I can find information on cleaning the slip rings? I am uncomfortable removing the brushes.

Thanks,

Ed
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Old 02-03-2017, 11:31:56 AM
Pete Spaco Pete Spaco is offline
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Default Re: Onan Emerald NHE Idle Problem

I assume that you have tried choking it to keep it running---
or have sprayed a bit of ether at it to verify that it is, indeed, a fuel problem?

Pete Stanaitis
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Old 02-03-2017, 12:20:00 PM
len k len k is offline
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Default Re: Onan Emerald NHE Idle Problem

My carb was from the newer version (NHM) of your gen, but it's very likely the same design.
On mine the 2 brass jet tubes were ~ 2 inches long and had 8 very tiny cross drilled holes that were plugged up. The 2 jet tubes screw into the cast dip tube that holds carb bowel on.

On my carb the 2 M & S air metering jets on TOP surface of carb were clean even though the 2 gas metering tubes in the bowel were mostly completely plugged. My carb had brass screws covering the M& S jets, some carbs have ball bearings pressed in and they can't be removed.

Here's a pic of my carb, ignore the arrows on pic,
#1 arrow .... under EPA cover disk is the idle mix adjustment
#2 arrow..... do not remove, nothing under it but a machined cavity for the 3-4 0.010" dia idle ports.
The M & S jets are above the #2 red arrow, between that red arrow and the vacuum diaphram.
https://www.smokstak.com/forum/attac...4&d=1341546175

Last edited by len k; 02-03-2017 at 01:15:34 PM.
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