Thread: What makes diesels smoke ?

I have owned diesel Landrovers for about 20 years I would not be too concerned re smoke on startup as on my 3.9 Isuzu the Edic motor (electronic diesel injection control) gives it a boost similar to the choke action on a petrol (loosely speaking) the only other time diesels will give off smoke (when engine and injectors are OK) is under full throttle with a load and probably going uphill or on sand with the engine working hard, other possible causes are dirty or worn out injectors, timing on the injector pump out of calibration and unfortunatley for most of us mere mortals that means a trip to the diesel specialist, by the way in my owners handbook for the 3.9 Isuzu it specifically states KEEP YOUR FOOT OFF THE ACCELERATOR DURING START-UP, so maybe read your handbook and see what it states re starting the engine, hope that helps cheers Dennis

Yep that pretty much tallies with what I thought.
Good to know I'm not a complete idiot. [img]style_emoticons/<#EMO_DIR#>/laugh.gif[/img]

Hi Vlad
Do the TDI motors have glowplugs?????? Pretty sure they do.
If so is your engine missing slightly or rough until warm-up ???????
Could be that a glowplug or 2 has failed,being in a warm part of the country it probably isnt so noticeable,but in winter where it gets nice and cold(like here) its easy to pick a glowplug playing up.
You can check if they are stuffed with a multi-meter if you remove them.You put a test wire on the top where the power connects and the other on the heating tip.Select ohms on your multi meter if no value is seen there is an open circuit and it means the glowplug is knackered.Glowplugs are removed as you would a sparkplug in a petrol motor.
Andrew

I would also think that the fact they are a turbo'd engine would have something to do with it. On startup I would say because the turbo is not "running" they would be overfuelled (I realise this happens when the turbo is not on boost but more noticeable on start) and hence the smoke on startup that clears once it is running.


Bushie

AFAIK, smoke with diesels is generally caused by overfuelling. At start up, more fuel is delivered to improve starting but will also cause smoke.

Surely Landy turbo diesels have the same technology as the jap diesels,my mitsa****y trytoo has a pressure tube from the turbo to a diaphram on the injector pump to increase fuel delivery as boost increases.
Andrew

High guys, i cant really say what is causing the engine to smoke, as said above i wouldnt be to worried about smoke on start up, there will be more fuel in the combustion chamber to kick the engine over when cold.
But what causes smoke in diesel engines, from a chemistry teachers point of view, is incomplete combustion. When a motor is started more fuel is added to help cold start up, having more fuel in there is just to make sure there is enough, the black smoke is the product of not all the fuel burning when the motor is started. A poorly tuned motor will produce the same result, either from to much fuel from dodgy injectors, or from not enough oxygen from a blocked air filter. You see for something to burn oxygen is required, just as when you light youre wood fire at home if you close the door and shut it down when you are trying to light the fire all you get is smoke. In a poorly tuned engine, where it is starved of sufficient oxygen to completely combust you get **** loads of black smoke and a dirty sooty engine. Start up is not really a concern, but when simply driving along the road at operating temp, black smoke shouldnt be observed unless under extremely high load. Even then a well tuned and serviced diesel engine shouldnt blow to much smoke, mine blows a bit up hit at high revs, but other than that it blows very little. Older engines will blow some as things are worn and not as good as they were when new. But if youre engine blows copious amounts of smoke when at operating temp, when you are just driving normally, i would drop it in for a tune, chances are its using to much fuel, or not getting enough oxygen. Matt

You also have to remember that Australian diesel is crap, which will not help either.

If you want to assure that you are doing the best thing for your motor use something like this product
http://www.fueldoctor.com.au/
it is cheap efficient and I have used it on alot of vehicles including the current freelander. As I am only on the second tank of fuel in this vehicle it is not a huge help in proof. However it turned my 95 TDI from smoking and using approx 7-8 Kilometres per litre and after about 3 months it had reduced the smoking and was getting approx 9-10 kilometres per litre