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Onan Emerald III - Cranks but will not start

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Old 04-24-2011, 11:51:08 AM
jmarxx jmarxx is offline
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Default Onan Emerald III - Cranks but will not start

I have a 1987 Holiday Rambler Imperial w/ 454 gas engine.
My generator runs off the main engine gas tank & is a:
Onan Emerald III Genset
Model: 6.5NHE-1R26100A
Serial: K860851752

It quit on me last summer while camping in an unshaded location with the air temp between 95 & 100 degrees. I was running both a/c units among other things. After several days of this, it sputtered a few times and quit. As this was near the end of our trip, I decided to wait until I got home to check it out.

The generator is full of oil & the engine tank is full of gas & the pull-out fuse on the generator is good.
I've have spark but no gas. I have a clear in-line fuel filter that I changed and can see that no fuel is being drawn through it.

I have a small Facet fuel pump mounted on the generator with 1 black wire going into the side of it. If I apply 12vdc to this black wire, my fuel pump operates & my generator will start & run.

Any guesses as to what component may have gone out to cause this problem.
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Old 04-24-2011, 07:51:10 PM
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TheToolman TheToolman is offline
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Default Re: Onan Emerald III - Cranks but will not start

1st Try a oil sending unit. That is usully it. I carry a spare with me it is so common.
Then maybe the brush set, But only if it has HIGH hours OR after sitting A LOT (this only happened 1 time in many years) Keep us posted on how its going
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Old 04-24-2011, 08:19:46 PM
Max Thompson Max Thompson is offline
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Default Re: Onan Emerald III - Cranks but will not start

I am thinking the fuel shut off, pump & coil are supplied from the same 12V source. You should have power to the fuel pump if you have power to the coil.
The above link is to the UN generator manual & has many wiring diagrams. It is slow to download, so give it time.

Last edited by Max Thompson; 04-24-2011 at 08:23:26 PM. Reason: add link
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Old 04-24-2011, 08:56:42 PM
kg5388 kg5388 is offline
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Default Re: Onan Emerald III - Cranks but will not start

trace the fuel pump black wire does it go to the control connector or a small black square or round box with 4 wire connections on it?

A few of the early ones had the fuel pump powered by ac output voltage through a recifier turning it to dc.

others where powered by the control board
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Old 04-25-2011, 10:43:44 PM
bbuchorn bbuchorn is offline
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Default Re: Onan Emerald III - Cranks but will not start

Unfortunately the UN manual doesn't cover the NHE spec A Generator you have.
Here is the link to your correct Spec A maintenance manual. In it, is a good troubleshooting section and wiring diagrams that should be for your unit.
The first question I have for trouble shooting is .... When you got it to run , was it making electricity? If not, the generator will not stay running, unless you hold in the start switch, and if the control board is bad, it may not even crank then. If the manual is as good as the one for my 6.5 NHE FA26100(E) you will find the resistance values for your windings and troubleshooting guides to check out both the regulator and controller card. There are a lot of things that can cause your trouble. try and check your brushes and slip rings first, check all connections for clean tight contacts, etc. Look at the back of your controller card for burnt traces, etc. It will take time but it is worth it . Good luck, and keep us posted. There is a lot of good expert advice on this board.
Good luck!
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