Engine Smoke

[dale farley]

I've probably reached my quota of questions in the last couple days, but I have another. I let my bus idle for about 15 minutes this evening then pulled out on the highway. When I took off, I got a terrible cloud of white smoke (obviously oil). It lasted for just a few seconds, but was really embarrassisng. I looked like a truck killing mosquitos.

It acted like a bad case of leaking valve seals, but that is normally most obvious when you turn off the motor then start it a few minutes later, allowing the oil to drip past the valve seals into the bottom of the head, then blowing it out when you start the engine.

Any suggestions as to what may have caused the smoke? I don't really know anything about the 8V92. Does it burn more oil than a 4 cycle diesel?

[JIM CHALOUPKA]

Dale, White smoke could be a coolant leak. JIM

[Jon Wehrenberg]

Ditto.

On a sub zero morning immediately after start up white smoke is unburned fuel. After the engine is running and had gotten warm my first thought would be what Jim said.

Smell it. You will know.

FWIW, I had a hairline crack between two valves in my 8V92 that allowed coolant into the cylinder. There are a number of reasons for coolant getting into the cylinder and none of them are good news.

[dale farley]

I suppose I will end up at Detroit Diesel for this one.

[Jon Wehrenberg]

Dale, before you take steps to mortgage the farm try to find out what the white smoke is. Smell it because if it is fuel or coolant you are going to know.

Coolant can turn out to be expensive, but fuel might be an injector.

[dalej]

One other thought, did by chance someone put a lighter oil in? You need a straight 40 weight in it. Also was it on high idle? A minute is max on low idle.

[dale farley]

Jon,

I really don't think it is fuel because it was over 60 degrees outside in the afternoon, and it should have been dark smoke if it was fuel. Once I took off and got down the road about 1/2 mile it ceased to smoke, even though I went 15 miles and stopped and started several times.

I will see what it does when I go back to get the bus in a few days, and if it repeats itself, I will attempt to determine the sourse by the smell of the smoke. I certainly vote for a bad injector vice a cracked head or other serious problem. I would welcome it being an injector that was leaking fuel in the head then burning/blowing it out when I accelerate. Thanks for the suggestions. Dale

[Jon Wehrenberg]

Partially burned fuel will be black.Typically that is what you see when you mash the pedal and the turbocharger has not spun up enough to supply enough air for complete combustion so the rich mixture is the black puff out the exhaust.

Raw fuel however is white. But so is coolant.

[dale farley]

Jon, I now better understand what you are saying about the injector. I called a couple Detroit dealers and one of them mentioned that it might be an injector. I asked why it wouldn't be producing black smoke, and he said because I would probably still be getting enough air to keep the smoke white. He said it will definitely produce white smoke if the injector is leaking, but the cylinder is still getting sufficient air.

I was thinking about an engine putting off black smoke when it is running too rich, but that could be from a lack of air just as much as an abundance of fuel.

The technician said the problem may be finding out which injector is causing the problem. He said it could be one of the small poppet valves sticking intermittently and may be difficult to locate. I hope to be able to verify it is a fuel problem the next time it happens. I see your last post validates exactly what the technician was saying.

[Jon Wehrenberg]

RR,

Maybe this is wishful thinking, but if I were Mr. Detroit Diesel my DDEC reader would be able to zero in on the problem, if not by accessing cylinder specific data, but by telling the solenoids (which are part of your electronic injectors) to stop firing so you can see which cylinder is least affected by the misfire, and thus may be the culprit.

You may be able to at least cut the number of choices in half by monitoring your pyros. If one has changed from its normal range at least that might be a clue to where to lok

If you can verify the white smoke is fuel with the sniff test, maybe a good run will be all that is necessary to deal with an intermittant problem and get everything back to working smoothly again.

If it is coolant I would drive it right to DD.

[dale farley]

Dalej,

I am sure the oil is straight weight Dello 40w. I've heard conflicting theories about idleing at slow or fast idle. What happens if you idle at slow idle for several minutes?

[JIM CHALOUPKA]

RR Dale, Wondering what the milage is and if there was any injector maintenance done recently. If you have high mileage and no records it might be prudent to rebuild or replace the injectors now for a trouble free start of your buss journey. Amsoil makes various cleaning addatives as well as synthetic oils and greases. You may be more comfortable with DD doing the work or you could make up an intermediate small tank to insert cleanerr to run through the engine without adding anything to the large tank. ;) JIM ( I am qualified to make things up. I hope this blurb is complete. I have to go to therapy now and I am late)

[dale farley]

Jim, The milage is 147K, and I am not aware of any injector maintenance. Are you aware of anyone who has been successful in solving an injector problem by just cleaning the injectors using cleaner in a small tank? Dale

[Jon Wehrenberg]

Dale,

Fast idle serves several purposes. When in cold temperatures fast idle will be required to maintain adequate engine and thus heating system temperatures. When using the AC / heating system on buses with over the road air the current draw is large due to the blower motors. At low idle your alternator might not be providing sufficient output to prevent battery discharge for extended periods.

If you are in traffic or will be idling for a short period of time, normal idle is fine.

Some diesel engines will load up with carbon if idled excessively, but I don't know if that applies to our engines. I know truckers idle all night long, but I assume they are on fast idle.

As far as additives, DD would be the best to answer your question. Generally regular use keeps everything working good, and when DD discussed this issue at a seminar years ago, the only fuel additive they recommended was fuel stabilizer if the bus would not be run for an extended period.

[JIM CHALOUPKA]

I do not know anyone and have not done it myself. I am only giving out ideas and tickeling the debate pot. :D:D JIm :rolleyes:

[Jon Wehrenberg]

Jimbo,

It's worth a try because if DD has something like that and it works, or even if they don't have something but recommend something and it works that beats pulling his bus apart.

I'm never that lucky.

I know one thing about these buses. They do not like to sit. Bad stuff happens. They need exercise and frequent use. Maybe all RR needs is to take it out on the road and run it.

[dalej]

Dale, when you are in low or normal idle, the fuel loads up and thins the oil on the cylinder walls, causing excessive wear. Do not idle more then a minute. Most of the time you are slowing down and the blowers or turbo cools down enough so as not to worry about turbo lock. Semi's that idle all the time are mostly inline 6's so they can idle forever. Don't treat a 8v like a inline. or 4 stroke.

[Ray Davis]

Wow, that is very new news to me. I've got an 8V, and don't remember anyone saying doing idle for over 1 minute. I routinely go to where I have the bus stored, and run it for over 20 minutes, since it normally sits for a long time.

I'm going to double check with my DD guy. I know when he's been over, and we're checking codes or whatever, we routinely start and let the engine idle on slow idle.

[Ray Davis]

FYI, I sent a note to my friend who is Regional Product Support Manager for DD, asking about idling on the 8V92. Although he didn't quite agree 100% on your assessment, it sure seems that I should be idling at high idle more.

Here's his response:


Regarding the idle issue, that is info is not 100% correct. Excessive idle will cause slabber, puddle of oil. Running at high idle is better to reduce slabber and better air flow in the cylinders but not absolutely required. If you idle for more then 15 minutes, you should kick it up to high idle for 5 minutes. No hard and fast rules.




Thanks for posting about using high idle! I wouldn't have known!

[dale farley]

Based on everything I have read here, I may have caused a puddle of oil on top of my cylinders that blew off when I accelerated. I had been on slow idle for about 15 minutes.

I had previously used fast idle for anything over a couple minutes, but I thought I was told that it didn't make any difference on this engine. Next time, I will try fast idle and see if I get the oil blow-by.

[Joe Cannarozzi]

I put catch containers on the 2 smaller tubes, I don't care for the mess it leaves behind, and once it warms up I shut it down drain the containers before I go. If I then use the high idle when resting or momentarily stopping for whatever reason NOTHING will reaccumulate in the jars. At an idle I have a pretty constant drip. I would like to believe that if we used it more that charicteristic would also be less.

I might add I empty those containers right back into the engine, it helps give me a better indication as to just how much oil its actually burning.

Currently we are right at 100000 miles on a rebuild that I am unsure of as to what was exactly done.

Dido Jons comment about the normal flow of heavy traffic being O/K for normal idle and dido Dales comment too. If I idled our bus for 15 minutes before rolling, even the best techinque with the throtle, and it would SMOKE. If ya just stepped on it it would be worse. The high idle automaticly goes off when you release the parking brake. I just leave mine on until I want to shut the engine off. Even though the strait-6 handles the long term idle well I believe it would be better to idle them up or shut um down.

[garyde]

On my Coach with the Detroit 60 Series the Manual says; " after starting , low idle for two minutes, to provide lubrication of the turbocharger. Before driving Coach, run engine at high idle and then check oil pressure."
It also states " with DDEC engines, the accelerator pedal must not be pressed down before starting. This will cause malfunction with the fuel system control. " It goes on to say " wait 30 seconds before starting engine if accidently depressed"
I go out and run my engine every 2 to 3 weeks for about 45 minutes. Gary

[Joe Cannarozzi]

Gary, ye know, both mine are mechanical the Cat and the Detriot as well.

At work as well as the club I'm surronded by computer controled stuff.

I always wanted to make a bumper sticker that said,

The best engines have throttle CABLES.:eek:

[dale farley]

I started this post several days ago because of an incident with engine smoke after an extended period (15 minutes) at slow idle. I took the bus to Detroit Diesel in Mobile, AL on Monday and got it back today. They performed numerous tests including cylinder cut-out test, injector response times, oil check valves, DDEC codes, etc.

They said the nature of the 8V92 2 cycle engine is to allow some oil to build up in the air box at slow idle, and then flush that oil through the check valves when under a load. In summary, they said my engine is working properly. Unless someone who has this engine tells me differently, I suppose I will take the DD's word as being the real facts in my case. The shop foreman also said they could reprogram my DDEC to smoke a little less from fuel, but said in every case they have done this, there is a significant power loss. One good thing is that they only charged me $166 for the diagnostic work. Thanks to everyone for your input.