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01-07-2017, 11:29 PM
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#1
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Member
Join Date: Sep 2011
Location: Chase, BC, Canada
Posts: 80
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Onan 7.5 quiet diesel smoke
My Onan 7.5 diesel started smoking blue on start up for a few seconds then it goes away. It doesn't seem to make any difference regarding ambient temperature. I have seen one other unit do the same thing but lots that don't.
It has 197 hours, I exercise it every other month under load and all fluid levels are good, there are no codes. It handles full load with no smoke or miss.
Does anyone have a quick answer or have it Happen to them?
Thanks, Bob
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2008 Winnebago Outlook 29B, V10 2011 Suzuki Grand Vitara
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01-07-2017, 11:51 PM
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#2
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Senior Member
Join Date: Dec 2009
Location: Out there, somewhere
Posts: 10,372
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With only 197 hrs, it's a pretty safe bet that the engine is not worn to any degree and therefore should be in great shape. Let me ask you something here.What is the ambient temp when you're doing your monthly exercise and start-up? You see, there is a starter/cranking delay for a given amount of time, based on the ambient temp. The colder it is, the longer the start button must be held down, prior to it actually cranking over.
This gives the glow plugs time to heat up, to assist the actual starting. If your unit is actually cranking and starting, right away, and it's fairly cold outside, it may be allowing some semi-unburnt fuel (in the form of blue/white smoke) pass through the system. It will do that for just a few seconds 'till that little Kubota 14HP 3 cylinder diesel starts to warm up even a little.
But, if you're pressing the start button and, you see green flashes on the toggle, and your engine is NOT cranking for a given amount of time while you're holding the start button, the system is working just fine. The colder it is outside, the longer the warm up time for the glow plugs. If that's the case, I can't help with the reason for your smoke. Good luck.
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2004 ITASCA HORIZON 36GD, 2011 GMC Sierra 1500 4x4 Toad '20 Honda NC750X DCT
 2018 Goldwing Tour DCT Airbag
Retired-29.5 yrs, SDFD, Ham - KI6OND
Me, Karla and the Heidi character, (mini Schnauzer)!
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01-10-2017, 05:38 PM
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#3
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Member
Join Date: Sep 2011
Location: Chase, BC, Canada
Posts: 80
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This unit did not smoke when purchased used. It was fine until it started to smoke about 2 years in to owning it.
We have friends with an 06 Tour, same generator, we travel with them on a regular basis, theirs does not smoke under same ambient temp. Location oil, etc.
It is light blue smoke, does it less when the ambient is higher, but only for a few seconds. Never misses and handles the load no smoke after this until the next time I start it.
Last summer we were in a site and a fellow with a Monaco had the same generator. It started and smoked just like mine. I talked to him about, he had the unit 3 years and just didn't worry about it. I would like to but that is just not me.
So Scott do you know what model of Kubota this engine is? I would like to pull the injectors and have them tested butt would like to do some research on it first.
Thanks, Bob
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2008 Winnebago Outlook 29B, V10 2011 Suzuki Grand Vitara
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01-10-2017, 07:21 PM
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#4
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Senior Member
Tiffin Owners Club Appalachian Campers Mid Atlantic Campers Coastal Campers Freightliner Owners Club
Join Date: Jan 2015
Posts: 1,622
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https://www.costeffective.com.au/New...ls-you-a-story
BLUE SMOKE is an indication of oil being burnt. The oil can enter the combustion chamber for several reasons.
Worn valve guides or seals
Wear in power assemblies (ie cylinders, piston rings, ring grooves)
Cylinder glaze
Piston ring sticking
Faulty turbocharger seals
Incorrect grade of oil (eg oil too thin, and migrating past the rings)
Fuel dilution in the oil (oil thinned out with diesel)
At cold start, blue smoke is often evident, and can reflect reduced oil control, due to fouling deposits around piston rings or cylinder glaze (which is actually carbon deposited in the machined cylinder crosshatching. These tiny grooves actually hold a film of oil, which in turn completes the seal between the combustion chamber and the oil wetted crankcase). Blue smoke should not be evident at any time, but it is worth noting, that engines with good sound compression can actually burn quite a lot of oil without evidence of blue smoke.
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DaveB, Raleigh, NC
2015 Tiffin RED 33AA, w/Honda CRV
VMSpc, Magnum BMK/ARC50
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01-11-2017, 08:20 AM
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#5
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Senior Member
American Coach Owners Club
Join Date: Apr 2016
Location: North Florida
Posts: 2,484
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I've seen a few that had fuel dilution
oil do this. My advice is service the gen-set, including air filter. Use the recommended oil.
Dilution can be caused by weak or defective glow plugs which cause added engine crank time before starting.
If still does it, perhaps add a oil additive like sea foam or whatever you like to clean piston rings and carbon
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1999 American Eagle
ASE med/heavy certified technician
ASE advanced diesel certified
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01-11-2017, 02:23 PM
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#6
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Senior Member
Join Date: Nov 2012
Location: bis. nd
Posts: 1,124
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not uncommon to get an injector to bleed down or is sticky an spits when not supposed to then warms little and goes away.. really doesnt hurt anything and not worth chasing..it does happen a lot in even the big engines but not as noticeable with the large exhaust and big cylinders.
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2007 Alfa Gold!! model 1008. 400hp Freightliner, IFS!!
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01-12-2017, 12:08 PM
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#7
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Member
Join Date: Sep 2011
Location: Chase, BC, Canada
Posts: 80
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Thanks to every body for participating, I appreciate your input. I will try some of these suggestion and have already done some. I have to put it on hold right now as it is -23 Celcius here right now and I am more inclined to hide inside. And thanks for the link to the information on diesel smoke, it was very interesting.
I would still like to know what model of Kubota this is.
Thanks, Bob
__________________
2008 Winnebago Outlook 29B, V10 2011 Suzuki Grand Vitara
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01-14-2017, 08:17 AM
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#8
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Senior Member
Join Date: Feb 2011
Location: Snowbird - Waterford Mi and Citrus Springs Fl.
Posts: 3,609
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It's been my experience diesels smoke on start up. All of them. No big deal, as long as it stops within a minute or 2.
Our 500 hr QD 7.5 does the same thing.
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1997 37' HR Endeavor, 275hp Cat, Freightliner
03 CR-V Blue Ox, Ready Brake
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01-18-2017, 12:18 PM
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#9
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Registered User
Holiday Rambler Owners Club
Join Date: Nov 2013
Posts: 215
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Start by adding a couple of cans of Seafoam to your fuel tank every forth or fifth fill up. Run the generator for more than your monthly maintenance check three of four hours. The Seafoam will clean the injectors in both the gen and your engine.
Mine used to smoke a great deal on start up, but ceased after changing out the fuel filter. Now that its changed and run for several hours it doesn't smoke except when really cold outside at the time of startup.
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