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Old 04-08-2013, 07:54 AM   #1
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Onan Generator Starting Question/Problem

I have a Onan Microquiet 4000 Gen in our 2008 Lexington 283GTS RV that we bought a couple of months ago and have a problem getting the Gen started. It has been used very little (30 TOTAL HOURS) and to get it started it must be primed 4 or 5 times and then let sit for 10 minutes or so. I don't know if the fuel filter might be clogged from non-use. The priming works ok since I can hear the fuel pump running when it is being primed. Any help will be appreciated. Thanks
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Old 04-08-2013, 03:30 PM   #2
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Hrrm sounds like something with carburator. A can of Onan 4c carb cleaner is inexpensive and might do the trick. Before you do that though Check the Altitude adjustment knob, it might be set for high altitude which would be difficult to start in low lying areas.
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Old 04-08-2013, 09:34 PM   #3
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I'm having similar problems. When we first got our rig 3 seasons ago, the generator was fine. When I primed it after a few weeks down time, the fuel pump would run at a high frequency and then slow down and stop, presumably when the carburator float shut off the needle valve to the float bowl. The generator always started within about 5 revolutions.

A year ago December, I needed an angioplasty procedure, and didn't get back to exercising the generator until April. It wouldn't start, exhibiting signs of very rich mixture. For a number of health-related reasons, I didn't get back to it until late February this year, It still has the same problem.

When we tried to get it running for this season, I still had the same very over-rich problem. I've replaced the fuel pump and both filters and have verified that the main-jet shut off solenoid is working.

I'm now leaning towards the conclusion that the float isn't floating. The prime pump sequence will run as long as I have my finger on the switch. When I try to start the generator, I get great gouts of black smoke followed by grey smoke and it quits, maybe 3 seconds run time.

The failure code is useless - it says "insufficient cranking speed" (code 32). I figure, if it fired, it was cranking fast enough. My next test is to take the float-bowl off the carb, leaving the float and its valve in place, and see if pushing the float to the "bowl full" position stops the prime. If it does, then the next step will be take the float out and see if it really floats when immersed in fuel. I suspect that it might not.

It's not a major catastrophe. At 11 years, the genny only has 50 hours on it, and we put the last 6 hours on. Almost all the generator hours are from the previous owner's and my exercising it during the off season. 50 hours in 11 years is very low utilisation. We very rarely stay at CGs where there's no mains power and we don't use both roof a/cs that often.

We'll probably head out for a few weeks towards the end of this month even if I haven't fixed it.
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Old 04-08-2013, 09:48 PM   #4
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Ethanol fuel sitting in any carb or fuel line is not good. If you have rubber fuel lines take the hose off the carb and see if it is deteriorated and collapsing. I had a new E-tec 50 horsepower outboard and after two years the fuel lines deteriorated so bad it caused major fuel pump and injector problems. Just saying it may not be your problem.
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Old 04-08-2013, 11:43 PM   #5
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Gas containing ethanol is bad news. It is horrible on gens and any small engine. I know some are not as fortunate and don't have stations near them that don't contain it. I do and fill my fuel station with 91 octane with non ethanol fuel. My gen fired up first try no problem this year and I did not start it once over winter. It states in a few different areas in the operators manual in big letters do not use gas that contains ethanol. My suggestion is if you have to get a good fuel stabilizer that is specialized in protection against fuels with ethanol.
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Old 04-09-2013, 08:22 AM   #6
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Quote:
Originally Posted by wyo700 View Post
Gas containing ethanol is bad news. It is horrible on gens and any small engine. I know some are not as fortunate and don't have stations near them that don't contain it. I do and fill my fuel station with 91 octane with non ethanol fuel. My gen fired up first try no problem this year and I did not start it once over winter. It states in a few different areas in the operators manual in big letters do not use gas that contains ethanol. My suggestion is if you have to get a good fuel stabilizer that is specialized in protection against fuels with ethanol.
Per a recommendation from a fellow RV friend, I use Sea Foam additive every time I fuel up, as I don't have any non-ethanol sources of gasoline. My hope is to prevent gen problems like this, and a plus is that it has improved my MPG by about 1.
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Old 04-09-2013, 08:42 AM   #7
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I don't know if those gensets have a fuel drain valve or a fuel shut off valve somewhere in line but if you must use Ethanol fuel it would be worth it to put one in. The damage is caused by the fuel sitting in the bowls and rubber fuel lines. Turn off fuel supply to genset and run it dry, drain bowl if you aren't going to use it for awhile. Ethanol added to fuel has been causing big problems for boat owners it is also eating up aluminum fuel tanks. Most Marina's now sell ethanol free gas. Here in Canada allot of the 91 octane fuel is ethanol free. At least in NB. A good place to check is
Ethanol-free gas stations in the U.S. and Canada it is what I use to find stations. Their is also an Iphone app and I am sure one for Android phones.
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