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Old 08-15-2022, 09:33 AM   #1
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Oil in my Air Filter on my Onan Marquis Gold 5550

I have 625 hours on this Generator and had no problems. Oil changes and oil filter changed regularly. I finally got it out for a test run and used the Generator and when running the heat pump to give me Air Conditioning while driving I went to back up and couldn't see in my mirror. I realized it was smoke I was seeing and nothing wrong with the mirror. I shut down the generator and when it cooled off I checked the oil. It was very low so I topped it up so it was showing almost full on dip stick. I waited till the next day to try and start the generator and it ran fine. I decided I should do an oil change and oil filter and check my air filter. When I opened the cover of the air filter oil dripped out and the filter is soaked and dirty. I'm wondering if it's because I didn't change my air filter after 450 hours that has caused the problem with the oil or could it be something else. I can't seem to find anywhere on the internet to answer the question "What can cause oil in an air filter on a gas generator". I have spent all day trying to find out how to post a thread. I hope I've put it in the right place.
Windsurferlady
35U Winnebago Adventurer
Kingston, Ontario
Canada
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Old 08-15-2022, 09:51 AM   #2
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If the filter was restricted and the crankcases breather is behind the filter, it could suck oil in from the engine. It would need to be pretty plugged and oil would go into the engine not really on the filter.

If the filter is packed with oil coverd dust, I'd say replace it and run it. If it happens again then you may have a blowby problem .

Blowby happens when the piston rings wear don't seal the compression in the cylinders.

Did you happen to start it with the filter off to see how much oily air is pushing out the breather hose ?
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Old 08-15-2022, 10:57 AM   #3
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Okay I was waiting to hear from anyone before I try anything. I didn't know if it would be safe to start it without the air filter. I took two pictures and will try and post them. If the breather hose is the small round hole that is where I'm to look right. The other I'm assuming is the carburetor or we used to call them on a car a buttery fly. The oil was on the bottom ridge of the air filter cover and ran off about a tsp. I'm working on finding out where I can order it from here in town. The Onan distributor is no longer dealing with them but there is a place that works on generators and she is looking up what the cost is for both the oil filter and air breather. It will be around 75.00 for both I'm guessing by the time the shipping costs are covered. I didn't know whether I should just go and have it fixed first or spend this much to see if by me putting oil in fixed the issue. That round silver plug below the drain plug has always weeped a bit of oil so I always kept a close eye on it. Because I haven't traveled or used it much I neglected to check the oil level before I went on this trip. I suppose even if the oil was low that isn't a reason to spew into the air filter. Now I'm starting to think it was low as there is another more serious problem than the filter being plugged. I'll try what you suggested of running it with the cover and air filter off and see what is taking place. Thanks for the help. I only know enough to be dangerous and have to reach out after that. Joanne
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Old 08-15-2022, 11:39 AM   #4
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At 200 p/h all the normal maintenance you do.. will save you.. I am going to assume you are out of warranty.. so I use hi quality fram oil and air filter.. in stock at most fram sellers .. less than 20... fram makes their stuff anyway and just relabeled for onan.. so if you love paying 4 times for parts.. ok with me.. go to fram.com and get cross over # and write down go get.. that out of way..

Don't change oil yet.. as Twin Boat suggests.. leave air filter off and run gen.. see if oil comes up into air cleaner housing.. get back to us on how much you see..
Gen has positive crankcase ventilation.. just like a car.. made just like cars in 70s and 80s.. even today.. so if oil is coming up crankcase vent.. we need to know..

Now I got to go.. be back later..
Good luck and keep us posted
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Old 08-15-2022, 01:21 PM   #5
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Is this spray coming out of the carburetor or the only other place is that little hole to the left of the carburetor. Can I hold a kleenex up in front of that and it will catch any oil spray? I've worked on this all day and am tired anyways but I'll do it tomorrow when I'm fresh and get back to you. This is in a 2001 Winnebago so it's definitely out of warranty.
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Old 08-15-2022, 01:35 PM   #6
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How many hours on the unit?
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Old 08-15-2022, 01:39 PM   #7
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The small hole to the left is the crankcase breather.

You should see sone slight puffing out of it but not oil drops.

Air filter is dirty but doesn't looked plugged up. Any heavy soot on the generator tail pipe ?
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Old 08-15-2022, 01:40 PM   #8
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Quote:
Originally Posted by randomledder View Post
How many hours on the unit?
Really ? it's in the first sentence.
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Old 08-15-2022, 02:15 PM   #9
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My sincere apologies. I missed that.
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Old 08-15-2022, 07:05 PM   #10
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625 hours
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Old 08-15-2022, 07:14 PM   #11
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Oops I just found my paper and it's 675 hours, good thing you asked or I would have put down the wrong number in my maintenance records. I'll check by the way tomorrow about the tailpipe soot. The filter to me looks like soot on it. I did find both oil filter and air filter at Carquest here in Kingston so I can do those replacements for $50. including taxes after we diagnose a bit more. I would hate to put that into it and it's something else so I'll do as recommended about looking at the crankcase breather tomorrow too.
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Old 08-15-2022, 07:59 PM   #12
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For starters I would change the oil and filters and run it to see what happens. At 675 hours if it hasnít been done I would definitely do a valve set, spark plugs clean the slip rings, inspect the brushes and a fuel filter. Also make sure itís running on both cylinders, there have been numerous magneto failures on these things and they run so smooth sometimes itís hard to tell. Is there oil anywhere inside the unit? Sometimes they will leak at the gasket of the crankcase halves. Just my two cents, but Iím the guy who missed the hours on the unit, take it for what itís worth.
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Old 08-15-2022, 08:49 PM   #13
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So I had a malfunction and don't see my second opinion.. while at part store.. grab 2 cans of cab cleaner.. not fuel injection cleaner.. pay close attention to what you are getting because the cans look the same.. but in fact are not.. get 2 or 3 very small toothbrush.. and some rags..
Now don't change oil and filter yet.. because I feel I see soot inside carb.. it's time for some really good carb cleaning and you must change the oil after carb cleaning.. so leave old old in for now.. also make sure you have Teflon tape..

Now I have to break this into multiple posts.. so bare with me.. I lost a big long one and maybe you got it.. maybe not.. yes there is a soot plug on bottom of muffler and you need to remove that 1/2 or 3/8 square head pipe plug.. we will come back to that..
Take white paper towels and rub that first butterfly which is your automatic choke.. there are 2 butterfly.. 1 choke and behind that is throttle..
So use all safety precautions and rag to catch back spray and spray carb cleaner on choke butterfly.. and toothbrush and clean.. engine off.. then use long screwdriver to gently hold open choke and spray carb cleaner in and on back of choke.. use toothbrush to clean sides of carb throat and sides of choke..
Next use long screwdriver to gently hold open throttle butterfly.. now you can't see this in bright sun light.. so use flashlight and look past throttle butterfly and on bottom of carb throat is your objective it is called main jet it will be a big hole..... Really spray as best you can.. next objective is to spray the tiny holes in top on carb inside throat sitting at top of butterfly.. good cleaning inside carb throat.. let sit while you do next post..
Good luck and keep us posted
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Old 08-15-2022, 08:55 PM   #14
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Quote:
Originally Posted by donr103 View Post
So I had a malfunction and don't see my second opinion.. while at part store.. grab 2 cans of cab cleaner.. not fuel injection cleaner.. pay close attention to what you are getting because the cans look the same.. but in fact are not.. get 2 or 3 very small toothbrush.. and some rags..
Now don't change oil and filter yet.. because I feel I see soot inside carb.. it's time for some really good carb cleaning and you must change the oil after carb cleaning.. so leave old old in for now.. also make sure you have Teflon tape..

Now I have to break this into multiple posts.. so bare with me.. I lost a big long one and maybe you got it.. maybe not.. yes there is a soot plug on bottom of muffler and you need to remove that 1/2 or 3/8 square head pipe plug.. we will come back to that..
Take white paper towels and rub that first butterfly which is your automatic choke.. there are 2 butterfly.. 1 choke and behind that is throttle..
So use all safety precautions and rag to catch back spray and spray carb cleaner on choke butterfly.. and toothbrush and clean.. engine off.. then use long screwdriver to gently hold open choke and spray carb cleaner in and on back of choke.. use toothbrush to clean sides of carb throat and sides of choke..
Next use long screwdriver to gently hold open throttle butterfly.. now you can't see this in bright sun light.. so use flashlight and look past throttle butterfly and on bottom of carb throat is your objective it is called main jet it will be a big hole..... Really spray as best you can.. next objective is to spray the tiny holes in top on carb inside throat sitting at top of butterfly.. good cleaning inside carb throat.. let sit while you do next post..
Good luck and keep us posted
What will that do for oil running out of the air filter housing or clouds of smoke out the tailpipe ?
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