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Old 05-13-2020, 10:58 PM   #1
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Onan gas 4000kw generator

Can't go anywhere do to Covid , so every couple weeks I go to our storage lot to check on our RV. Of course run the engine and generator. Fuel tank was even filled up couldn't resist $1.57 a gallon, plus exercised our Thor ACE 30.1.
Problem gen a few times started hard but started and ran fine. Well last week it wouldn't start. Went outside primed then tried. It fired died instantly . Several times. Check gas flow and there was good flow. Spark fine. I figured after checking oil level ( full ). Maybe carb plugged or dirty. Pull had checked at local carb shop , they said no dirt , clean and could not find issue. Now the real issue , re installed. Engine wouldn't even fire. Now noise like something loose in engine is present. Not rod but like something dragging or rubbing on flywheel. Gen has 353 hours on it an has been well maintained. Guess I'll have it pulled. Seems to be mechanical now. Any thoughts????
Thanks
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Old 05-14-2020, 06:00 PM   #2
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Crank no start condition. Do you have fuel flow? Is there a spark? Do you have compression? A mouse hasn't moved into the air filter? Something rubbing on the flywheel would probably only prevent the crank from spinning.
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Old 05-14-2020, 07:57 PM   #3
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Originally Posted by raffaelli View Post
Crank no start condition. Do you have fuel flow? Is there a spark? Do you have compression? A mouse hasn't moved into the air filter? Something rubbing on the flywheel would probably only prevent the crank from spinning.


all you've asked has been done. Re read my post. Flow is steady, spark is fine. Air cleaner and carb are immaculate. Compression at factory specs. Changed plug anyways. Check oil level. Noise inside engine is not right. Thanks for response.
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Old 05-14-2020, 09:50 PM   #4
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So the generator would not run after starting.
You had it worked on by somebody.
Now it won't start and it cranks with an abnormal noise.
Why isn't it back to "somebody's" shop?

They obviously broke more than they fixed.
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Old 05-14-2020, 10:58 PM   #5
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Onan gas 4000kw generator

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Originally Posted by 16ACE27 View Post
So the generator would not run after starting.

You had it worked on by somebody.

Now it won't start and it cranks with an abnormal noise.

Why isn't it back to "somebody's" shop?



They obviously broke more than they fixed.


Well it was pulled an is at their shop now. I have no doubt that it is something they did. Could be a fluke, doesn't matter I have a full warranty. Just a pain. I did talk to Cummings Onan, and was told most engines aretrouble free. Life expectancy 300,000 hours if maintained. But Onan also mentioned that there has been a problem with valve keepers coming off and dropping into engine. Not real common but a known fault. They were very helpful and told me if this is the issue they'd cover it. Even gave to me in writing.
Now that's customer service.
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Old 05-14-2020, 11:53 PM   #6
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Originally Posted by Luke D View Post
Well it was pulled an is at their shop now. I have no doubt that it is something they did. Could be a fluke, doesn't matter I have a full warranty. Just a pain. I did talk to Cummings Onan, and was told most engines aretrouble free. Life expectancy 300,000 hours if maintained. But Onan also mentioned that there has been a problem with valve keepers coming off and dropping into engine. Not real common but a known fault. They were very helpful and told me if this is the issue they'd cover it. Even gave to me in writing.
Now that's customer service.


300,000 hours? Thatís 34 YEARS!
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Old 05-15-2020, 12:04 AM   #7
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300,000 hours? Thatís 34 YEARS!
Yeah, I think someone got too many zeros on that answer.
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Old 05-15-2020, 12:06 AM   #8
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300,000 hours? Thatís 34 YEARS!


Wow your scarring me. At 100 hours a year that's a 30 year life. That's actually the design life. I was off two zeros. Me bad fat fingers typing. 3000 hours is the design life. Cummings/ Onan state in writing that the gen set should far Outlast the RV. The Cummings Onan dealer here in Tampa have a 4000kw microlite on a test stand running an it's at 4200 hours. Still running.
My goof
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Old 05-15-2020, 12:10 AM   #9
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300,000 hours? Thatís 34 YEARS!


Yup fat fingers......3000 hour design life

Me bad... Sorry
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Old 05-15-2020, 03:02 AM   #10
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Wow your scarring me. At 100 hours a year that's a 30 year life. That's actually the design life. I was off two zeros. Me bad fat fingers typing. 3000 hours is the design life. Cummings/ Onan state in writing that the gen set should far Outlast the RV. The Cummings Onan dealer here in Tampa have a 4000kw microlite on a test stand running an it's at 4200 hours. Still running.
My goof


Geez now Onan corrected me....design life 30,000 hours. Yup thirty thousand hours. Ok one Zero
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Old 05-20-2020, 08:14 PM   #11
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Any chance your oil level is TOO full? Too much oil has the same effect as low oil - gen won’t stay running.
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Old 05-20-2020, 09:17 PM   #12
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Any chance your oil level is TOO full? Too much oil has the same effect as low oil - gen wonít stay running.


Check for low oil an overfill, oil on stick just below full mark. Clean and fresh. Still waiting on word from Onan
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Old 05-20-2020, 10:58 PM   #13
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Fuel Consumption

I thought I remembered reading somewhere that the 4kw gas generator will consume .6g either in a 1/2hr or hr. Can't remember. I believe the post was by ducksface. I can't find that post to save my life.
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Old 05-20-2020, 11:05 PM   #14
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Going out on a limb here, but I still think it's the carb. Probably some gunk somewhere in one of the very small passageways.

I had a similar issue where one day it fired, sputtered real bad and then wouldn't start anymore. Took the carb apart, it looked clean. Submersed it in a can full of Seafoam overnight, reinstalled and have been good since.

Just a thought . . .
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Old 05-20-2020, 11:07 PM   #15
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I thought I remembered reading somewhere that the 4kw gas generator will consume .6g either in a 1/2hr or hr. Can't remember. I believe the post was by ducksface. I can't find that post to save my life.


My understanding from what Iíve read and seen on an onan 4kw is under a loaded condition it is .6 gallons per 1/2 hour. Now that was a chart showing 3/4 to full load. At 1/2 load I believe it was .4g. As you I am trying to re tract down the data. In actuality I seem to remember all kinds of variables, temp, humidity altitude etc. mine right now does not run so fuel consumption great lol
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Old 05-20-2020, 11:14 PM   #16
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My understanding from what I’ve read and seen on an onan 4kw is under a loaded condition it is .6 gallons per 1/2 hour. Now that was a chart showing 3/4 to full load. At 1/2 load I believe it was .4g. As you I am trying to re tract down the data. In actuality I seem to remember all kinds of variables, temp, humidity altitude etc. mine right now does not run so fuel consumption great lol
Not glad to hear it's not running but following in case you find it again. Yes, I imagine all those factors will have some impact on efficiency.
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Old 05-20-2020, 11:15 PM   #17
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Originally Posted by VetPartTimer View Post
Going out on a limb here, but I still think it's the carb. Probably some gunk somewhere in one of the very small passageways.



I had a similar issue where one day it fired, sputtered real bad and then wouldn't start anymore. Took the carb apart, it looked clean. Submersed it in a can full of Seafoam overnight, reinstalled and have been good since.



Just a thought . . .


Thanks wish it was carb. It might have been part of the original fire and die issue. The shop soaked it in sea foam and stated it look great. But after re install , internal engine noise, definitely something mechanical appeared. Waiting on Cummings Onan people here in Tampa for direction. Iíll keep you posted. Thank goodness I have a warranty.
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Old 05-20-2020, 11:16 PM   #18
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Originally Posted by VetPartTimer View Post
Going out on a limb here, but I still think it's the carb. Probably some gunk somewhere in one of the very small passageways.

I had a similar issue where one day it fired, sputtered real bad and then wouldn't start anymore. Took the carb apart, it looked clean. Submersed it in a can full of Seafoam overnight, reinstalled and have been good since.

Just a thought . . .
If it's not run enough, gas will varnish and clog the jet(s). Other areas are more apparent but jets are hard to see unless you pull them.
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Old 05-20-2020, 11:24 PM   #19
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Not glad to hear it's not running but following in case you find it again. Yes, I imagine all those factors will have some impact on efficiency.


Everyone on this forum is awesome. Thanks so much for being so helpful. As a former classic car mechanic I hear you about jets. Very true. I even thought about buying a new carb. Quite the dilemma. Amazon $69.00, Onan $326.00. same carb??? Can't be but sure look identical
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Old 05-20-2020, 11:25 PM   #20
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Misaligned sail flap/switch?
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