Onan 7.5K DKD Diesel Genset blowing white smoke at startup

[rvwarrior]

Hey guys, (Gary, Carl, Russ and gang)

Hope all of you are well,

As most of you know, recently I replaced the exhaust manifold on the that genny

Then, a week later, the generator quit and it turned out to be the lift pump. Had it replaced and she was back to running good again

She's got 3000 hours on her, I run this thing for about 12-15 hours a day quite frequently and right now, it appears that she's running very good

Here's the problem. When I start it now, it blows out a good amount of "white smoke" for approximately 45 seconds. Sometimes, it will blow white for up to a minute give or take. There will also be a smell of oil associated with it.

Additionally, when she starts, it seems a little rougher than it has in the past, but once she's all warm, it seems to level itself off and sound normal again.

Any suggestion? Could this be a sign of a potential larger problem looming?

I'm going to throw this out there, but could it possibly be that my "glow plug" is going bad? Do glow plugs go bad? Do they need replacing at some point?

As always, I look forward to hearing your thoughts

Currently, Tina, Otis and I are up in Concord, NH on the way the White Mountains to ride the tramway and check out the Flume up at Cannon Mountain.

Beats sitting in a cubicle wouldn't you say!?

Warmest,

shad

[Russ Chastain]

It doesn't sound good.

White smoke indicates burning oil (as does the smell of oil you mentioned).

Very little oil should ever be present in the combustion chambers of your engine, which is where it's burning.

I think (and someone should correct me if I'm wrong) that the only way the oil can get in there to burn on your engines is it it's making its way past the piston rings.

The rings seal the bore of each cylinder, to keep burning gases out of the crankcase, and to keep the oil in the crankcase and out of the combustion chambers.

When rings and/or cylinders get worn, they can leak at that seal (the rings).

You lose compression and you burn oil. Eventually the engine won't run because it's worn out, and will need to be overhauled.

Make very sure to keep the oil level topped off, because you're losing some oil each time you fire it up, and possibly while it's running.

Someone else here will be better able to provide specific advice on what steps to take next. Me, I think you can keep using it for now, but expect to have it rebuilt or replaced in the not-too-distant future. But I am an amateur, and I could be wrong.

[RV Mech Tech]

White smoke indicates burning antifreeze (smells similar to burning oil) , blue smoke indicates burning oil- have the head gaskets checked- you probably have coolant leaking into a cylinder(s) from a coolant passage (gasket has blown through between coolant passage and cylinder- a pressure test of the cooling system will tell you) - oil can enter past worn piston rings, and valve guides, and in rare cases a crack in a cylinder head from the valvetrain area into the intake passage (aluminum heads) and also on a V-8 through a defective intake gasket from the valve lifter area - your generator has an inline engine.

[rvwarrior]

Good replies so far,

RV Mech Tech and Russ,

If it's a head gasket, what would a repair ($$) typically run?

So far, my oil or coolant levels have not gone down.

So, a pressure test of the cooling system should tell me if it's a head gasket?

s

[RV Mech Tech]

rvwarrior- you can have antifreeze only leaking into the combustion chamber or combustion gasses leaking into the cooling system -if its the latter then there is a chemical test to check for contamination of the antifreeze- if ant. is leaking into the combustion chamber then a pressure test will tell you - if the gasket is leaking the cooling system will loose pressure - if allowed to continue damage to that cylinder(s) will result - you will have an inline 3 or four cylinder diesel (engine make depends on when it was made) but the service procedures are the same - if the generator is on a slidout drawer and the engine is easily accesable then it takes less time to remove the cylinder head and replace the gasket- the engine block and cylinder head have to be checked for other damage as well and the cylinder head may have to be resurfaced -(some diesel cylinder heads cannot be machined/resurfaced if damaged - the Oldsmobile 1980's diesel is a good example) prices will vary depending on who does the job - a generator shop may charge you less than a regular RV dealer or garage - a small amount of coolant leakage will cause smoke for a short time on start-up but a major leak will keep pushing antifreeze into the cylinder and not stop- you said that it lasts for only a minute or so and this would indicate a small leak at this time - sometimes contaminated fuel will cause smoke of some type but if this was the case it would not stop -

[rvwarrior]

Thanks for the in depth replies

Unfortunately, I don't have my generator on a slideout drawer

My unit is from 1995-1996, DKD Genset

If by chance, I have a damaged cylinder head, can mine be machined/resurfaced?

Right now, because my family and I live in the Motorhome and are traveling full time, I run this baby 15 hours a day, everyday

This sounds like I need to get this in to the shop to get checked as soon as possible - damn!!

Knowing that it's not on a slideout drawer, any "guess-timate" on what this might run me? I'm trying to prevent getting gouged!!

s

[rvwarrior]

Mr. RV Mech Tech,

I was just googling a few things a read about others having white smoke problem

Is there any chance that I could have a Thermostat issue?

s

[RV Mech Tech]

rvwarrior- smoke coming out of any exhaust tells you that something other than the intended fuel is in the combustion chamber and when you shut off the gen. then it will collect a little bit in the chamber and when you start it up that stuff will be burned and be visible out the exhaust and you said it was white smoke ( oil burning will be white smoke with a slght tint of blue ) so its possible ant. is leaking into the chamber and this will be pure white smoke with an acid smell to it - a stuck coolant thermostat (stuck in the closed position) will cause a higher operating pressure in the cooling system and possibly be the main cause but not always (if it is antifreeze then the thstat should be replaced as well) - most diesels have a coolant bypass in case this does happen but one way or another something is getting into the chamber- where is your genset located? an Onan 7.5 K is a big gen so it should be in the front of your coach- the panels around the generator are removable and there may be a removable panel in the coach floor for servicing the gen- there is probably a flat rate fee for the actual job on the gen but getting to the gen is what makes the costs vary on RV's- each one is different - and on some of them (better get a streacher for this one) the gen may have to be removed from the coach - I have done two of these Onan diesels like that and its not fun! - this is why its important to have it diagnosed correctly and I would suggest doing this at an Onan dealer (you can locate one through the Onan website)- they can also give you an exact cost for the gen repair itself- whatever they have to do thats required to obtain access will be on an hourly basis (this is the way Onan in Ontario does it)- and as I said if the head is removed the block and head will have to be checked for warpage and cracks or other damage - if for example the head is cracked a generator shop may have a used one they can install - it all depends on what the problem is- let us know what you find and good luck!

[rvwarrior]

Thanks again for your help on this

My Genset is located on the front

There's isn't a "floor panel" to speak of. The genny is of course bolted to the frame, then it's just open ground below that

Well, I'm scared, but wish me luck

I'll let you know what I find out

s

[Rob98801]

just something else to ponder.

On one of my little diesels a bad injector gave clouds of smoke until it heated up then all was fine. I had the injector repaired/replaced by a diesel shop and after that no more smoke signals.

[Mickey]

Since this is a diesel engine, oil is what they burn so need to be careful what you read into smoke signs.

Don't know what engine is in the genset so comments are general in nature.

Is there a glow-plug for each cyl or is there a heated grid that heats the air during intake cycle? Glow plugs can and do fail. They are small heaters and give up the ghost. If one or more have failed OR for some other reason glow plugs are not getting any power at start-up time. One or more cyl may not be firing initially and takes a little while for cyl to heat up to point combustion oil ignites.

My tractor usually starts without the use of the glow plugs but as the weather cools, sometimes all cyl don't fire if I don't use the glow plugs. There will be signs of one cyl not firing and light colored smoke for a short while is an indication.

[rvwarrior]

Hey Rob, Mickey (and gang)

I just looked through my generator schematics

I can't find wich engine is in my genny exactly, but I know there are (3) glow plugs

I started her up this morning and it blew white again for about a minute, then leveled off after it was warm

Then, it seems to run excellent

Checed oil and coolant this morning. Both look fine and normal

Cleaned spark arrester

I've got an appointment tomorrow at 1PM with a Generator place here in New Hampshire called J&D Power Equipment, Inc - I'm hoping they can tell me a few things

Any other thoughts before I head into the belly of the beast?

s

[Rob98801]

My only suggestion would be not to run the generator before you get to the shop. Then, start it up only when the tech's are standing there.

My vote is for a bad glow plug or a dirty/bad injector.

[rvwarrior]

Yeah, I'll leave her cold until I gt to the shop

"My vote is for a bad glow plug or a dirty/bad injector."

I am on the same page. That would also get my vote

Hopefully this will be the case

Here we go!

s

[Cal]

Just my 2 cents
Dark smoke = poor combustion!
White smoke = something other than pure diesel in the combustion chamber/s!
It was stated before and nothing will change it.
Put your hand in the smoke if it feels wet it's water/ anti freeze.
Oily and it most likly is engine oil.