Smoke on Startup

[first230sl]

I searched through the old postings (love the new forum's search by the way) and there is a fair bit of discussion on smoke at startup.

When I start my 8V71TI's reasonably warm (not been run recently but have the Kabola heating them), they start immediately and produce some blue/white smoke (does not dissipate) for a couple minutes. Then they clear completely.

When I start them cold (in, say 50 degree weather with NO pre-heating), the smoke is worse, and it takes a few tries to start them. They catch and die a couple times, and on the third or fourth try they catch, hunt for maybe 30 seconds, and settle. Sometimes a tiny bit of throttle is required to get the first light. The smoke eventually clears completely.

Should I be concerned about the smoke, slightly difficult start, and RPM hunting? They were just tuned. How much smoke is too much smoke? They do not use oil in any apparent quantity.

I know much of this has been discussed, but I haven't seen any quantitative discussion of how much smoke is too much smoke. I mean - does a few minutes of smoke really matter? Who cares?

Also - I always turn them over for about 10 seconds with the kill switch engaged to bring oil up before starting. Would this increase the initial smoke?

Just trying to gain some perspective here.

Take care - Murray

 

[MikeP]

I'll add what my 8v71Ti's display...


On cold start up with ambiant air temps in the low 40's, they light off immediately and produce substantial clouds of blue/white smoke. They will hunt for maybe 10-15 seconds. It takes probably 2-3 minutes for the smoke to reduce to the level where mosquitos can safely return to the area. The engines continue to lightly smoke which will never completely clear with the boat sitting at the dock, regardless of the RPM setting. Thermostats are 160's and engine temps will not rise above that at the dock, even at no-load WOT. Water temps here at the moment are in the low 40's. At ambiant air temps in the 50's, they will not hunt at all, but settle immediately to idle. With the block heaters on and engine water temp in the 110 range, the engines are harmless to mosquitos but will lightly smoke as described earlier.

If the boat is in gear and operating, the smoke clears. There is none at any RPM setting...as long as the engine temps are above 175. This leads me to the conclusion that these engines are happier when operating in the 180 range, rather than the lower end of the temp scale. DD temp specs per the service manual are from 160-195 so there is a pretty wide range involved.

My port engine had 180 Tstats in it for some reason (Star had 160s) when I bought it. The port engine ran temps of 194 at 1800 RPM which scared me. When I discovered the stats were 180's I replaced them with 160s. Now it runs around 175 at 1800 RPM. But it didn't smoke at all after it was warmed-up with the 180s.

I posted a question about T'stats/smoke on the marine diesel forum but got no replies. But the proof is in reality anyway, not on advice. The engines don't smoke at 180 degrees; they do at lower temps. I am not saying all is OK because there is a 55 Searay next to me with DD's and it smokes only briefly at start-up with one pretty big puff and then and clears completely very quickly.

The engines have approximately 350 hours since overhaul in 1998 but the boat was hardly used for two years between 2002-2004. There could be some stuck ring or other issues causing what I consider to be too much smoke although airbox checks of everything were fine at purchase last year. It seems to smoke more now than it did then. Fuel is from last November - whether that's an issue or not, I won't know until I refuel. I have been thinking of running a fresh batch of fuel through the engine with the fuel pickup and return lines sitting in a 5 gal bucket of fresh diesel. Whether I actually will or not remains to be seen.

 

[Nonchalant1]

I wouldn't worry about yours. Get an engine heater if you're worried about smoking out the marina, but at ours when you hear the deep rumble of diesels, you can always tell who just started up by looking for the smoke.

My 8V71TI's do this:

I don't have engine heaters, don't pre-crank, and 375 hrs SMOH.

If starting cold after sitting a few days in 40 degree weather, they light on the 2nd of two 5 second cranks. They hunt for about 10 to 15 seconds, then idle. They both smoke clouds of white smoke for about 1 minute, gentle smoke for a few minutes, then completely clear at 650 idle.

If they have been run that day, they start instantly and no smoke.
No smoke at any speed or operating temperature under way, unless I accelerate hard and then I get light black haze diesel smoke as the engines are revving up.

Doug Shuman

PS - There's a guy who swears that his bbq grill set off a cloud of diesel fumes wafting across the marina in Michigan. Says it just went "FOOM" and didn't start fires or blow anything up.

 

[capt4fish]

I ran a 46' Bert. that had 892's, It would smoke pretty good at start up, would get better as it got warm but would never go away completely, until you ran it. After running and getting back to the dock it would not smoke. These engines had 4900 hrs without any rebuild. They have since been rebuilt and only slightly smoke on start-up and it goes away completely very quickly. I ran a 55' Hat. that had 12v71's, after a fresh rebuild they would start, smoke slightly, ( or heavily if it was cold) but would clear up very quickly, and completely within a couple of minutes. When a piston went bad the engine would smoke badly at start-up never clear completely but would clear significantly, while running you could not tell there was a problem, other than it would not turn up. When you got back to the dock the white smoke would return. If you suspect you've a problem, have your mech. dead out each cylinder until he finds a weak one, then have that cylinder compression checked, or have the injector changed, which ever the mechanic diagnoses. Either way, Detroits are usually fairly easily diagnosed
by a compentent mechanic. Tight LInes.

 

[Pascal]

can't say anything about starting in 40deg weather obviously... coldest i've fired the 8V71Ns in must have been in the low to mid 50s.

in average weather like in the past month, 60/70, on a cold start, mines start right ayay, not even 1 second cranking and will settle around 5/600 rpm within seconds of firing up. Port sometimes seem to be about to loose fuel so as soon as the Oil pressure climbs up, i give it another couple of 100 rpms which seems to help. same engine which has lost prime in the past...

Port never smokes at all, hard to believe but i've never seen anything coming out of the exhaust, I always go to the stern after i fire them up to check for smoke and water flow and by the time i get there, it's clear with no lingering smoke. Stbd smokes a little, 10seconds, maybe 15 at the most, then the smokes stops completly.

less visible in summer, a little worst in "winter"...

engines were supposedly rebuilt 6 years/500hr ago although paperwork was minimal and survey revealed some wear on the crosshatch patern incosnistent with the low hours advertised.

funny story... the first time i heard about DD smoking was a few years ago, when the owner of a trojan express docked next to me at a marina in the keys, asked us to close all hatches, and step back 50' because he was going to start his engines and "DD always smoke a lot" .... no kidding... for the next 10 minutes, I couldn't see my boat from 50' up the dock!

 

[MikeP]

I read recently somewhere

that the definition of "Detroit Diesel Engine" is, "A device for converting Number two diesel fuel into noise and smoke."

Seems right!

 

[first230sl]

Thanks everyone. It is very helpful to get some perspective on this.

Next mechanic visit I'll mention the hunting when cold - but I am not going to worry about the smoke I have. Seems par for the course and a long way from the Trojan Pascal saw in the Keys.

Thanks everyone!

Murray

 

[SKYCHENEY]

Weather in the 50's, my 6v92's with 3300hrs had white smoke for only about 30-60 seconds and then cleared completely. This was at launch after winter storage and the service manager at the marina said, "Boy, those must be naturals." I told him no that they were 92's and he couldn't believe how quickly they started and how fast the smoke cleared (no heaters). I think that this situation has improved ever since I started using Diesel Kleen. Maybe it's just my imagination, but I really think it has helped to reduce smoke. Any thoughts?

 

[Genesis]

Diesel Kleen boosts cetane which significantly helps cold start smoke.

Hunting on a cold start is not unusual at all. If you have hunting once the temp gauge is off the cold peg, you need a tuneup. Not a big deal but should be looked it. Usually just a buffer screw adjustment, but the governor gap and rack should be checked.

 

[neosin]

cold start with smoke for a few mins + some minor rpm hunting = leaking fuel injector maybe?

Mine did the same thing, port side engine would smoke for about 3 - 5 mins or until warm in 85f weather. Found out it was 2 injectors leaking slowly after the last run after shutdown.

Have someone check them. Or if they are old replace them. That way you know what you have in there. One of mine leaked so much once it bent a rod which cause that piston to not get complete conbustion... which led to the engine never quitting smoking and i almost had to get some smoking patches nicoderm CQ? Boat had a problem.... lol replaced 2 rods, problem was G O N E....

I would say if your smoke gets any worse or if you see it lasting any longer than what it has been, check into it...