White smoke from diesel engine

nevster

nevster

Member
Joined
30 Jun 2003
Messages
33
Location
East Sussex
Visit site
Went to boat to day to do some work. Decided to give engine,MD2B, a start as it hadnt been run up for about three weeks. On starting there was some white smoke coming out of exhaust and this continued to come out whilst engine idled for a while. Is this because engine has been standing, should I be looking for a problem or am I just worrying. I seem to remember seeing a post saying about various coloured smokes from diesels but cant find anything and cant remember what was the right colour to be. Any help gratefully accepted.

Mark
 
I think it relates to unburned diesel but i wouldnt worry until you have warmed it up properly and given it a good run.
 
I have got one of those, lots of nice folk keep telling me it is smoking, usually calms down after a few miles, but does start first time, and has never let me down.

Relax!
 
I had a couple of Perkins 220`s that always gave off a lot of white smoke on start up, in eight years they never gave any trouble but I’ve always wondered why?
It couldn’t be glazed bores as the engines always did it.
Could turbo oil find it`s way into the inlet manifold or is it excess fuel on cold start , I dunno.

...........
 
Some white smoke at start is nothing to worry about. It is unburnt diesel fuel in the form of atomised spray from the injectors, and occurs when the fuel sprayed from the injector does not all burn. Unlike petrol engines, for various reasons a diesel may ignite only a part of the fuel in the combustion chamber, and unburnt fuel passes through into the exhaust appearing as white smoke. The cylinder temprature has to reach 600C + before the fuel will ignite on cold start. If the cylinder compression is down marginally, the initial heat from the compression is unsufficient for the fuel to ignite except in the vicinity of the heater plugs. White 'smoke' appears at the exhaust until the combustion chamber has warmed up enough to allow complete ignition. It is a symptom of a part worn engine, and can be ignored UNLESS it continues once the block has reached working temprature. In that case it can be symptomatic of a range of problems from underfuelling (insufficient fuel reaching the injectors due to blockage or slightly aerated fuel) to valve or cylinder problems preventing fuel from burning off properly. Certain injector faults can also cause it. The general; advice is that as long as the smoke has more or less cleared within a couple of minutes from cold, there is nothing to worry about. I have seen a 450,000 mile Peugeot taxi that smoked for over five minutes from cold, but would run happily the rest of the day.

Also after excessive cranking without actually starting the exhaust system can becoime soaked in fuel oil, which then evaporates off producing a lot of white smoke as the engine warms up. Most marine engines have watercooled exhausts which wash the oil out without vaporising it, though.

"Could turbo oil find it`s way into the inlet manifold or is it excess fuel on cold start ..."

Excess fuel on cold start will cause the characteristic puff of black smoke often seen on start up, particularly on large slow revving marine diesels as seen in commercial shipping where overfuelling is needed to get the engine up to speed. Many smaller engines also start at full throttle, plus an extra dollop, then go to tickover as soon as the engine fires, producing a puff of black smoke.

Turbos can dump lube oil into the manifold with spectacular and sometimes destructive results. If the oil seals fail sufficient oil can get into the inlet manifold to run the engine. I very recently had to deal with a charged Perkins with a badly worn turbo that was not only feeding oil direct to the manifold, but was causing suffient crankcase pressure at near full throttle to force lube out of the breather into the manifold. The engine ran away on its own lube, producing a huge volume of grey smoke even after switching off, running up to 6 -7k revs before the breather pipe came off and saved the day! The engine itself was undamaged, and after fitting a new turbo is now running quite happily again!
 
As with 99% of other boats ??

Now I was told :

White smoke is too much air, not enough fuel.
Blue smoke is oil
Black smoke is too much fuel, not enough air.

Many say that white is due to atomised diesel on start up ... mmmmm I dunno on that .. as it seems that engines normally build up fuel when starting then chuck out some when started ... but when that's happened with mine - its a black whoosh and rainbow streaks across the water ... But I have to really have throttle open for that ....

Others will talk about water and steam ... but engine is not hot enough yet ....

If it stops or goes real low after a few minutes run - then IMHO - it is same as many other boats and will most likely run for years ...... without change.

It was funny .... last time in Yarmouth, nice family in their boat across other side of pontoon downwind of me - before I started my Perk - I advised them after 30 odd years of use my engine may smoke a bit ... they appreciated the warning and went below while I got her running. NOT a wisp ... not a hint of anything .... unbelievable.
 
Mine has black smoke on startup followed by white smoke when running. The white smoke does not clear, so I guess I have a problem. But my engine is 30 years old.
 
[ QUOTE ]
Good answer. Nothing to add....

[/ QUOTE ] ....except most complaints of white smoke on boats is actually steam from the coolant in the hot exhaust. Genuine diesel white smoke looks very similar, but is much more pungent in smell - and I wouldn't recommend a lungful of it! Check that enough water is getting through to cool the exhaust. On some engines like the Bukh, it is normal. If the smoke varies according to air temperature - lots on a cold day, noticeably less on a fine day - then it is steam.
 
Hi, you seem to know your stuff so I would be grateful for some advice. I have a Yanmar 27Hp diesel outboard (yes a diesel outboard!) it's a great engine, uses next to no fuel, grunty and basic! The trouble is that I am getting whitish grey smoke on start-up and it continues after the engine has warmed up, it smells of diesel exhaust. I recently put some redex deisel in the fuel as it was getting troublesome to start and I thought the injectors may be a little clogged, it quickly went back to it's one turn starting but then this smoke started getting worse. I have also been using some old fuel, maybe that is the cause, although this has been pretty much diluted with new stuff now. The blokes in bars have various opinions from catastrophic to don't worry about it.
ANY ADVICE WOULD BE WELCOME!!
 
"Old fuel" - how old? Diesel (and petrol) can be stored for quite some time before it detriorates provided containers are sealed and are not translucent. Believe it or not light is what causes fuel to go stale.... But Diesel will store for a long time before problems start. BUT was it clean? Was there any likelihood of contamination or condensation in the storage tank? If so theres a good chance your fuel system is contaminated and needs cleaning (new filters, service injectors).

Have you noticed any power loss? reduced revs at full throttle and whiter smoke indicate either partially blocked fuel system or a very slight air leak in the system.

But if Redex reduced the problem for a while, then maybe the old fuel has mucked up the injector spray patterns. B4 doing anything though take it out and give it a good thrash for an hour or so - full throttle all the way in! Carbon build up in the cylinders and exhaust will cause poor starting and smoking and working it as hard as you can periodically will clean it all out. I commute in a diesel car - and it just hates it. A good run 20 - 30 miles down the fast lane of the M27 fettles it up nicely for the next 2- 3 weeks!

If that doesn't work: check for any trace of leakage in the fuel system. Wipe each joint dry, run up for 10 minutes then check joints with a coloured tissue - any oil present will darken the paper making it easier to identify if there is a leak. If oil is coming out - air is getting in and causing the smoke.

Next thing is to have the injectors out and the spray pattern checked. If you can shift them yourself, most dealers will check them while you wait if you take them along to the workshop when things are a bit quiet.

After that things get more complicated and need specialist attention: injector pump faults, valve problems or cylinder problems all of which need workshop facilities to check out properly. At least you can take the beast to the mechanice raher than pay him to come to you!
 
Thanks a lot for that, I will keep you posted if you don't mind! Have a daysail planned for the weekend so will give it a blast down the harbour, so if anyone sees a cat doing 10kts down Portsmouth harbour with a trail of white smoke, please have some sympathy!!
 
White smoke= Water vapour, not a problem if it stops once the engine's warmed up in which case it's probably just condensation in the system, if it continues check head gasket and for water in oil.

Black smoke= Worn injectors, incomplete combustion, get 'em reconditioned or try new air filter first

Grey/blue smoke= Burning oil, worn pistons/cylinders, engine recon most probably required.

IMHO.
 
You must log in or register to reply here.

Other threads that may be of interest

Jon magowan
White Smoke from my Engine
Replies
11
Views
462
Ian_Rob
I

Share this page

Top