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

22 Replies

DrewE
Explorer II
Feb 02, 2018
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.
Farmboy666
Explorer
Feb 02, 2018
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.

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Onan Generaor - 10 yr old

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