Smoke on cold start
 

My 1987 300 SDL smokes badly on cold start up----replaced glow plugs thinking that was problem but still smokes very badly on cold start-----doesn't smoke at any other time---no smoking on warm start....Car runs fine-----188000 miles..Is there a temperature sensitive sensor that richens fuel supply when engine is cold and could this be mal-functioning? Would appreciate any and all help-----I don't have much mechanical knowledge....

What color smoke? Does it run rough or stumble on cold start, like you have to keep your foot to the floor? Do you notice any coolant loss?

If its white, your probably in big trouble.

Turbodiesel, thanks for your post-------the smoke is grey-blue with slight fuel odor-----starts easy and fairly smooth idle since replacing glow plugs but still heavy smoke until achieves normal operating temp .....no coolant loss....Hope can resolve this problem because otherwise this is a near perfect vehicle.....I'm impressed by the mileage on your 87--- have you had to do much to it?-----this is the first frustration I've had with mine.... 87 300SDL 87 300E 85 380SL 82 300D 81 240D 80 450SL 79 450SL 78 280SE (2) 81 300SD

Your experience with the 1987 3.0-liter diesel engine is fairly common. My 300D provides a good cloud of smoke for the first two minutes or so after startup. The problem seems to have been resolved to some extent in the later model years by letting the glow plugs run for awhile after startup. In 1986-87 the glow plugs stop right at engine start when you release the key. I have given some thought about a modification to the glow plug relay controller that will keep the glow plugs on for awhile after start. Something like a timer module to go inline with the connector that provides control signals to the glow plug relay.

My car has done this since I've had it, which is only a few months.

I'd like to know if this is something that has just started for you, or if the car has always done this.

Thanks,

Ken300D
1987 300D (332K Miles)

Ken, thanks for some great thoughts on the problem----I bought the car at 95k miles and no smoking problem until 150k.....your thinking makes sense to me.....have you at any other problems in particular with your car......thanks again, lbeeman.....Indiana

Erm
 

What does white smoke mean? My car has white smoked in cold weather ever since I bought it. Replacing the glow plugs helped a little, but we're about to find out for sure because this morning is coldest this year I think, and Im about to go start her up.

Very interesting - I suppose there could be something getting weak or going bad that causes the smoke - possibly an injector or two. However the car runs great after the minute or two warmup.

I read somewhere on here that a weak injector can "leak down" after the engine has stopped and spill fuel into the cylinder from residual pressure supplied by the injection pump. But that doesn't explain why the car never smokes on a (more) warm startup - even up to eight hours after running.

There might be something wrong that is causing the smokey startup, but the car runs so well otherwise that I'm not going to deal with new glow plugs, injection pump, injectors, etc. to stop it. I'll just drive.

The classic cause of pure white smoke (fluffy, like clouds in the sky) is water. The water has to come from somewhere, like a leaky head gasket. However, you don't want to confuse in panic the smoke we are talking about for "water vapor" smoke. The smoke we are talking about is light gray - maybe with a little bluish tint to it - and smells pretty strongly of unburnt diesel fuel. A true white cloud due to water wouldn't have much smell I don't think.

Ken300D

Yeah
 

Its not fluffy white, but its grey white and it goes away immediatly after starting the car and never returns. (To start it in cold weather I have to jam on the gas after a double glow)

lbeeman,

Your engine is just not combusting the fuel properly for some reason, hence giving you some grey smoke, i'm not really sure about the problem, someone else can probably fill you in.

I bought the car with 220K miles a year ago and have only had to put a vacuum pump in. As far as I can tell, the engine and transmission are totally original.

John

Ibeeman,
Have you tried the trick of waiting 10-20 seconds after the glow plug light extinguishes? This practice made a giant difference to my 87 300d, settled the idle down much more quickly. OTOH, perhaps with new GPs this is not so significant.
The other suggestion is getting the injectors serviced. You hear different stories regarding injector servicing on these cars, everything from 'it's not a scheduled item' to 'get it done every 50,000kms on an IDI engine'. I bit the bullet recently, had the tips replaced and the injectors calibrated. I noticed my start up plume of blue-grey smoke had disappeared and what did appear on occasion was a faint wisp of darker coloured emission. A huge difference, as was the general cleaner running, idle steadiness, willingness to downshift, and (gasp) acceleration. I thought it ran well beforehand; I think the 603s hide loss of tune because of their smooth running.
Your comment that it smokes until reaching 'normal operating temperature'. That is going to take several miles - does it smoke while you are driving it 5-10 minutes after cold start? I'd have thought fuel leakdown or residual fuel due to poor ignition should be cleared fairly quickly one the idle settled down, in say 1-2 minutes.

good luck,
Philip.

Unburnt fuel is my vote.

Philip and DW-----thanks for you replies-----I'll try the trick of delaying starting until aftr glowplug light goes out-----interesting idea-----was injector servicing a particularily expensive procedure?---Thanks again, Lee

lbeeman,
I'm a diesel novice, so the cost of the injector service took me by surprise, over $US300. I live in Australia, and the costs here won't be relevant to you. I have read figures of $50 per injector in the US but I may be wrong about that. It looks to be an easy job, but what do I know? Certainly a specialist job. The injectors in my car looked to be rusted in, so it looked like they had never been done before (212,000 kms) so the shop had some work to do to clean them up. Guys like psfred can probably advise on cost to you. Maybe check around your area, see a good indie shop.
It did make a big difference though.
cheers, Philip.

What differences did you notice? Start/idle/running? All the above?

My 91 300D does that too. Although #2 glow plug is short but I don't think it has that much effect. I guess the valve stem seals have something to do with it after you shut it down for a long period.