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Old 08-19-2007, 10:22 PM   #1
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Onan NH-RV GenSet 6.5KW

I did a search on surging before I posted this and found several good threads on this issue. However, I couldn't find one exactly like mine so I thought I would start a new post about my particular issue.

When I started out in Ol' Nancy well just over a week ago, We started out in Texas. Whew, it was so hot. Nancy was a coach that had seemed to have been fairly well maintained up until maybe 3-4 yrs ago. I am the 3rd owner. The po before me had passed away due to illness and I believe he took regular care for her until he got sick. Anyway to the point.

The generator started right up when I first got her. It ran fairly well, but seemed like when you put a load on her she would start to surge. Nancy was at an RV dealership / service center. A technician there was fixing the blower on the dash a/c for the widow of the po of which I purchased her from. The tech told me that he thought the surging was due to a restriction in the fuel line or maybe the carberators needed cleaning.

We ran the generator all the way home to sweet old Barbourville, Kentucky which is about a 900 Mile haul. The generator didn't seem to surge too bad after she warmed up. There was a circuit breaker under the dining area that was turned off, so we only ran the one a/c plus the fridge. We stopped at campsites along the way and had shore power of which we didn't need to use the generator.

I turned on the breaker switch and had Nancy using both a/c units. Saturday when we decided to go camping I had both a/c units going and the fridge going. She didn't start surging until about 20 minutes later after we stopped at a place to wait to meet someone to return our great nephew back to his mom and dad. After the surging began we could not get the generator to run very long at all. After we got back home from camping today, I decided to see if I could get the generator to start and keep running. I disconnected from shore power at my house and turned off everything in the coach and tried to get the generator running. I changed the spark plugs the oil and oil filter. I could not get it to run hardly at all. The plugs were soaked with gas and the generator seemed to be flooding out. Not until I started messing around a little bit with the electric choke could I get it to run, but very rough. I gapped the plugs to .025 as suggested in the manual, the plugs were some knock off brand as well as the oil filter. I wonder if I am on the right track. I would take it to a certified Onan service center, but the Cummins dealership is 50 to 60 miles away. It will be a while before I can make that haul. I guess I may fiddle with it again tomorrow evening after it cools off a bit.. Again, any advice would be appreciated.
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Old 08-19-2007, 11:22 PM   #2
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Tinker Toy

That sounds exactly the same way our Onan was acting.
Did all kind of fuel delivery tests.
Would not even run smooth on a shot of either.
Was getting worse every time I worked on it, very ego busting.
Ran out of time, as a road trip wasd approching, so had to spring for a new one.

Really want to here what you end up finding out, as mine was running wisper quite before bad gas problem showd up.
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Old 08-20-2007, 05:50 AM   #3
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Quote:
Originally Posted by klattu
That sounds exactly the same way our Onan was acting.
Did all kind of fuel delivery tests.
Would not even run smooth on a shot of either.
Was getting worse every time I worked on it, very ego busting.
Ran out of time, as a road trip wasd approching, so had to spring for a new one.

Really want to here what you end up finding out, as mine was running wisper quite before bad gas problem showd up.
The older Onans surge for many reasons. I have one mounted on a wagon which was removed from my brothers RV and has only 60 hours on it. I set it up to use for Hurricane evacuation. I had to clean the carburetor due varnish from old fuel, lubricate and adjust the linkage. If you perform a Google search you will find several sites devoted to the Onan Generators, many were used it the GMC camper units. The best advice I can give is do some shopping on ebay and purchase the factory manual on disc and print it out. Get a good multimeter one that reads frequency, voltage, and temperature. Get a good stool and spend some quality time with you Onan generator the TLC will ensure that the ONAN loves you back. No reason why the unit won't do 10,000 thousand hours before Overhaul.

I don't think anything runs smooth on ether. I use it when I have to. On a Diesel I use WD40 the propane propellant give you a shot to turn the engine and the oil gives you lubricant. I learned that trick from an old Diesel Mechanic.

jagcb759, check your needle valve, it sounds as if your float is stuck due to vranish mine had glued it self to the bottom of the bowl and flood the engine I to could get it to run playing with the choke. Check your float level also. The electric choke is tricky did you mark the orginal postion ?

Check all your filters as a unit which has sat will pickup a lot of trash in the fuel line when put back into service due to the bottom of the tanks being stired up by road motion. Very bad on boats, the engine dies due to clogged filters as soon as the water gets rough.

When you get it smooth and adjusted, load it up heavy I use an old electric Kiln and check that it will hold the load for severeal hours. Don't use your ac or tv to load the unit find something which low voltage or high voltage won't damage.

Good Luck
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Old 08-21-2007, 10:15 AM   #4
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Here is an update:
I worked on it until 10:00pm last night. I took off the carbs and intake by removing the 4 bolts as suggested in the manual. the carbs looked clean. I took off the bowl and checked the floats and it looks emaculate. Everything was clean. I found some residue at the top of the carbs where there used to be a gasket that went in between the carbs and air breather tube. It looks like it had worn out. I need to replace it. The manual told me how to adjust the two set screws. 1 is for idle mixture and the other is for main gas level (throttle I guess). I found that the main one was loose. I sinched down the brass nut and woked the needle in to seat it so I could back it out the recommended amount. But I noticed that the needle looked out of round. So I backed it all the way out and I found some of that black sticky gasket material like that was above the carbs. I am assuming that that gummy gasket may have been sucked in through the carbs and got stuck on the needle where the spring tension is at. So I cleaned it off and sinched down the brass nut and screwed in the needle. The needle didn't look out of round anymore. Backed it out the recommended amount and put her back together. It purred like a kitten. However, when I put a load on it it would start surging. The GenSet did seem to run very quietly. I think I need to set it up a little. It was showing 120 Volts in the coach at a recepticle above the sink. The lights seemed a little dim. The refrigerator worked fine, but when I turned on the front a/c, the surging began. The manual has a section in it that tells me how to adjust the carbs. Then it seems like it suggests working on the governer.
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Old 08-21-2007, 09:02 PM   #5
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well, it looks like I spoke too soon. I went to start up Nancy's GenSet today and it was back the way it was before. Flooding like crazy. could not even get it to start back up. Looks like it has beaten me. I will have to seek the help of a pro. I guess I will have to make the haul over to a cummins dealer to get it serviced.
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Old 08-22-2007, 02:42 PM   #6
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I just got to give it one more go. I am going to tear into it one more time. I will remove the carbs again and this time I am going to completely dissassemble the float / needle valve assembly and inspect the needle valve. I still believe that the problem lies in this area. Everything I have read leads me to believe that there is just too much gas in the float bowl. I will inspect to see if there is some kind of vent tube that may be stopped up. I worked on an atv a couple years back and a dirt-dabber made a nest in a vent tube and it took me forever to figure out that it was the problem. I adjusted like crazy on the float and done everything, but there was so much gas that it was backing up into the air box. This is a similar scenario, but I don't know if the two carberators are made similarly in that respect.
I will post back with my results. Genset = 2 / JaG = 0........
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Old 08-22-2007, 04:51 PM   #7
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don't forget to see if the floats are porous. you'll notice that when dry they become much lighter. redip in fuel after drying and see if they feel heavier.
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Old 08-22-2007, 09:06 PM   #8
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@richinny: my floats are made out of tin like metal.

update: I cleaned the whole carb with carberator cleaner. backed out the main adjust screw and cleaned it. the seat looked good. backed out the idle mixture screw and cleaned it and the seat looked good. took the needle valve out and cleaned it and the seat looked good. sprayed carb cleaner with the little red hose in all the holes I could find. Did not find any vent tubes. put her back together and again it purred like a kitten. this time after 10 minutes of smooth running I started adjusting the carbs as suggested by the operators manual. It seemed that the genset was running great even after I put a full load on her. It wouldn't allow me to set the governor down to 100volts on the low end though. I couldn't get any lower than about 118 volts. I then as one of the last steps was to adjust the main fuel adjustment but could not get the voltage to drop until I almost seated it all the way in. So I ended up getting it all out of whack again i think. Still it didn't start surging until I turned one of the a/c units off. It stayed surging until I held back on the governor a little and tried to smooth it out. I will try again tomorrow.
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Old 08-22-2007, 10:30 PM   #9
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Onan the Carbarian

At least you know where the problem is...the carb.

Found some new ones on Ebay for $150 +/- based on model.
Think I will try that when I get back to Onan
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Old 08-23-2007, 03:44 PM   #10
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@klattu: I hate to hear you are having these problems too, It sure has been nerve-racking on me. I wish you luck with yours and let us know how it turns out for you.

Here is an update:
I tore into that sucker again. This time I took the needle valve and float out. The float is made out of a material that is like tin. I bought some carb cleaner and cleaned everything. I sprayed it in every orfice I could find. I backed out the main fuel needle and sprayed it down. I backed out the idling mixture needle and sprayed it down and put it all back together. I started it up and it purred like a kitten again. then I got the manual out and started tinkering with the governor assembly. After messing with the tension a bit by how the manual stated, I was able to apply a big load on her. 2 a/c units and the fridge. She took the load quite well. I let her run for a while. After I tried turning off 1 of the a/c units. She started to surge again. Then I ran and shut down the 2nd a/c unit so it wouldn't be damaged from the surging. and it kept surging. I could run out the the Genset and pull back a little on the governor and the surging would subside. I think I am getting close. If I can't adjust it out, the book states to change the spring on the governor, because it may have gotten weak.
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Old 08-23-2007, 03:47 PM   #11
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An Onan tech told me that surging is usually caused by the governor spring weakening. You might try replacing the spring. Mine is running fine now.
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Old 08-23-2007, 03:52 PM   #12
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@Cooperhawk: Wow we must have posted at the same time. With the same answer.
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Old 08-23-2007, 03:54 PM   #13
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Wink

Just goes to show that great minds think alike.
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Old 08-23-2007, 04:51 PM   #14
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Onan 6.5

HI! I to had the surge problem and took mine to an authorized Onan repair shop here in East Texas. They kept the MH for 7 months before they said it was repaired...said that the choke was the problem. Took the rig to the crawfish festivel and Onan ran for about 6 hrs and started surging again..Thru my hands up and bought another unit off of e-bay. Other Onan is back at the repair shop for about 4 months this time...hope your luck beats mine!
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