We have a Onan Marquis Gold 5500 watt generator. It is 10 yrs old. I service oil and air filter. We have never had a problem with it. It has 500 hrs run time. When it used to start it would crank then run smoothly almost immediately. Now when cranked it sort of putt, putt, putt, putt, putts, for 10-20 seconds then runs smoothly. Trying to decide if I should take MH in to get generator serviced. However not sure what they would do. Would they clean carburetor, or replace it? other? Or would they tell me it is 10 yrs old and I ought to buy a new one? Or is this the expected behavior when 10 yrs old and it is ok, this is normal, no service needed.Wish I had more confidence in the service folks. Seems like when you have a MH they think money is not an issue for you. We are still making payments. What are your thoughts?

It sounds like a fuel issue but 20 seconds really isn't an issue. Does it get fuel from main tank or it's own? Either way I would try some Seafoam first and that should help clean things up if it's fuel system.

I rather doubt it's the carburetor since it's running well once it gets going. This sounds to me more like an initial fuel supply problem, either insufficient priming (often done by holding the control switch on stop for fifteen seconds or so before starting, though I don't know about this particular model) or a fuel pump that's getting weak or maybe a pinhole or not quite tight fitting in the generator fuel line allowing air in and fuel to drain back to the tank between uses.It's possible that the choke linkage could be a bit sticky or need some adjustment, too.Any of these should be pretty straightforward for a competent shop to figure out and fix, depending somewhat on ease of access. If they tell you to get a new generator, go elsewhere; that's crazy talk.Especially as this is new behavior, I wouldn't call it exactly normal or proper, but it doesn't sound especially troublesome to me either, so long as it doesn't get too much worse and has trouble starting when you need it.If you ask about things in the Tech Issues forum, you'll likely get better answers from people who (unlike me) have a very thorough knowledge of these generators.

If you determined to have someone look at it call around to the small engine service places rather than the local RV dealer. All they do is small engines day in and day out. Just because it's bolted to an RV doesn't mean it's something strange or exotic that needs a RV guy to look at it.Although run time is low it might need a bit more maintenance at this point in it's life then oil and air filter replacement. Finding a local small engine tech who will assist can make life a little easier. Don't forget the mobile mechanics either.

I am not a rocket scientist and always follow a good post. Although only 7 years in my MH, I have noticed a similar situation. I do the routine maintenance, have similar usage hours and exercise it on a load 2 hours a month. I am of the belief that the start up lag, more noticeable in colder temps of course, is about priming and then fresh gas getting through. Once it kicks in, runs smoothly.

You service the oil and air filter. Do you change the generator fuel filter?If someone tells you it needs to be replaced because it's 10 years old. Don't walk, run away.I have a 1996 Southwind with the original Onan 5000 generator. It woeks great. I agree with running some Seafoam through the fuel system.

Onan Generaor - 10 yr old | Good Sam Community

Passin_Thru
Explorer
Feb 14, 2018
i thought of it because I saw a movie where a guy was mad at his girlfriend so he brushed the dog's teeth with hers.
77rollalong
Explorer
Feb 12, 2018
my onan has and electric choke pull off (1977) the newer ones have a vacuum pull off, i had to rebuild the carb for ours last year it did run , but was a bit hard starting at times. I had picked up a can of industrial carb cleaner and soaked all the metal parts in it , (no plastic or rubber) as this cleaner will remove the paint and eat anything not metal. i also added an extra inline fuel filter with a clear case as i know there is junk in my main fuel tanks as i have not had a chance to drop them and have them steam cleaned as yet. there is really not too much too the carbs and the orifices are quite small so a little bit of crud messes them up. I also found that the previous owner had put the choke pull off spring in incorrect so as it heated up it would give it more choke instead of taking it off..
Jim
Explorer
Feb 12, 2018
Passin Thru wrote:
If that one has the automatic choke (not sure if its auto or heated intake) the solenoid on the mixture solenoid could be going bad. Pull the plug with 2 wires to it from the float bowl and clean with a carb cleaner and tooth brush, preferably your wife's. They usually cause surging. It's a very easy fix.

Buhahahahah. Snort. Thanks for that.
Passin_Thru
Explorer
Feb 12, 2018
If that one has the automatic choke (not sure if its auto or heated intake) the solenoid on the mixture solenoid could be going bad. Pull the plug with 2 wires to it from the float bowl and clean with a carb cleaner and tooth brush, preferably your wife's. They usually cause surging. It's a very easy fix.
Rick_Jay
Explorer II
Feb 11, 2018
TC&Z,

I agree with checking out the choke. But before you do that, is there any possibility the altitude adjustment got bumped when you were working on it? Our Onan has an adjustment for the altitude for which it's being operated. Depending upon the altitudes and/or setting involved, if it's not adjusted properly it might look like a choke problem on start up.

Good Luck,

~Rick
mcal63775
Explorer
Feb 11, 2018
Use Seafoam every time you fuel. If you are be able to get premium WITHOUT ETHANOL, that will be a plus. Exercise your rig at highway speed least once a month, running generator. Use the levelers and slides. A sitting rig will deteriorate way faster than one getting used.
sehunter
Explorer
Feb 03, 2018
I agree with Richard my generator was doing the exact same as yours. I visited our local Onan shop and was told they have replaced hundreds of the vacuum chokes on the carburetor, it sounded like there is a service life on these things. If you are able to service your RV you are more than capable at replacing it.
roam1
Explorer
Feb 03, 2018
sounds like the automatic choke to me to, as they get older they can stick and take a bit longer to function.
ArchHoagland
Explorer
Feb 03, 2018
I use Seafoam once every year. I put 5 to 6 cans in the gas tank just before a long trip.

During that trip I'll run my Onan 5500 for at least an hour.
koda55
Explorer
Feb 03, 2018
I agree with everyone that has said to use seafoam. I use it in all my gas engines.
Our RV has a 150 gallon tank and I put 3/4 of a gallon in the diesel every 4 months. I run the generator about 1/2 load for about an hour to make sure it gets into the generator.

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Onan Generaor - 10 yr old

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