Onan generator problem

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Alik6853

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Mar 5, 2021
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Fb
I have 4500 watt Onan generator after couple hours shot down.what could be the problem?
 

uchu

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Ontario, Canada
There are many possible causes (low fuel level, low oil level, dirty air filter, etc.). More information is needed about the conditions when the shutoff occurs.
 
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DonTom

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Auburn, CA or Reno, NV or Cold Springs Valley, NV
I have 4500 watt Onan generator after couple hours shot down.what could be the problem?
Almost countless things. Does it crank? If so does it ALMOST sound like it is going to start?

If so, what you can do is go take the door off the generator and use the switch you see there that says "start" and "prime". Press the "start side" of that button, the generator should crank and perhaps start for a second and shut off. Then the red light on that same switch will probably blink three times. Then press the switch to the "prime" side quickly. Now you will get new blinks. Say it blinks twice and then a delay and then blinks five times. That means the error code is "25". It will repeat the code several times, so if you miss it the first time, just get the code the 2nd time.

So what you have to do is get that error code and then we can go on from there to diagnose the problem.

-Don- Auburn, CA
 

Alik6853

New member
Joined
Mar 5, 2021
Posts
3
Location
Fb
Almost countless things. Does it crank? If so does it ALMOST sound like it is going to start?

If so, what you can do is go take the door off the generator and use the switch you see there that says "start" and "prime". Press the "start side" of that button, the generator should crank and perhaps start for a second and shut off. Then the red light on that same switch will probably blink three times. Then press the switch to the "prime" side quickly. Now you will get new blinks. Say it blinks twice and then a delay and then blinks five times. That means the error code is "25". It will repeat the code several times, so if you miss it the first time, just get the code the 2nd time.

So what you have to do is get that error code and then we can go on from there to diagnose the problem.

-Don- Auburn, CA
Thanks for your help appreciated.
My son had it check by some mechanic shop who they work on a generator.
What they saying is that
The technician found that the cylinders have low compression. The engine is work. We got a quote from the parts department and Yesenia is working on an estimate for repairs.
$ 5662.00 for repair or $ 4162.00 replace for new one.
My question is if is low compression how come starts after couples hours
Working just fine then stops after couple hours starts back and this happens when weather is to hot also I know this when my gas fuel goes blew half I have hard time to start the generator Please advice me what should I do?
 

Isaac-1

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SW Louisiana
Can you post the model number of the generator, I can't think of any 4,500 watt models Onan has built in at least the last 35 years.
 

DonTom

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Auburn, CA or Reno, NV or Cold Springs Valley, NV
When your RV fuel tank is low, the generator should NOT start. This is so the RV cannot run out of gas, leaving you stranded, by running the generator. That is normal, usually happens at around a third tank but it varies a lot.

IOW, the generator should run out of gas way before the vehicle does. That is normal.

-Don- Auburn, CA
 

Old_Crow

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Mammoth Lakes, California
When your RV fuel tank is low, the generator should NOT start. This is so the RV cannot run out of gas, leaving you stranded, by running the generator. That is normal, usually happens at around a third tank but it varies a lot.

IOW, the generator should run out of gas way before the vehicle does. That is normal.

-Don- Auburn, CA
I'm always careful to keep my tank above 1/4 tank just so I can run the generator if I have to.
When we got towed to Kingman last Nov. I had been trying to get out of Cali before buying gas, so the gauge was just above 1/4 tank.
We ended up having to spend 4 days waiting for service(a weekend was involved)and ran the generator a lot. I kept watching the gas gauge and it got well below 1/4 tank and the generator never quit. I carry an extra 5 gallons, so it was no problem to refuel the coach, but I was really surprised about how low the gauge went.
I probably should have just run the generator until it quit to find out how much gas was left, but it was cold, rainy and spitting snow. Was just easier to keep gas in the tank.
 

Ernie n Tara

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Ft Myers, FL
Frankly, it sounds more like you have some vacuum leaks in the fuel lines than low compression. I had both the symptoms (actually saw the case where filling the tank converted the non start to a generator that started) you describe and that was the cause.

Low compression, on the other hand actually improves as engine parts expand with heating and improve the sealing. I'd find another shop!

Ernie
 

Ex-Calif

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It runs for a reasonable amount of time. It auto shuts down. Won't restart until it cools down.

Also it is correlated to hotter weather. Also it "seems" to start harder with lower fuel tank levels.

If this were a car I would be thinking fuel system, vapor lock, etc. etc. I don't know if this thing has a fuel pump or a fuel filter or if it is mounted higher than the fuel tank, level with the fuel tank.

I don't agree with the compression diagnosis at all. I would be doing stuff like cleaning fuel lines, investigating if I had a fuel pump, changing the fuel filter and tuning the mixture to be a bit leaner.

I also would be thinking overhaul the carburetor way before I spent $5500 to "repair" or $4400 to "replace" - Which also makes no sense. When I see things like that coming from a mechanic, I just read into it so many "bad" things about that mechanic. The first being that this one has zero troubleshooting skills and the second one is he may make his money on gullible rich RV owners. The third one is that he is not really a "mechanic" and just throws parts at a problem.
 

Mark_K5LXP

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Albuquerque, NM
Just thinking about my own onan, doing a compression check would not be a trivial effort. If this is an installed unit it's not like it's a 10 minute thing to do, so was it actually done?. Engines rarely "suddenly" develop a compression problem, usually ring wear over an extended time and it'd be unusual for it to be so bad the thing wouldn't start at all. With all the other issues that typically happen to small air cooled engines, compression as a failure would be very low on the list. I would seek a 2nd opinion.

Mark B.
Albuquerque, NM
 

jubileee

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Dec 17, 2013
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672
I’m betting compression test was done by ear. As in “sounds like it might be low on compression “.
If it was a competent shop, and they did a compression test, they also would have done a leak down test to come up with repair estimate.
 
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