Diesel engine producing black smoke - why?

Question

After a few goes, the smoke started to clear a bit, but it was pretty bad on the first couple of goes. What's your diagnosis?

This is on a diesel electricity generator (big). We tested it on load, but not full load (maybe 1/3).

The smoke is coming from the correct place of course (the exhaust)

PS the generator hasn't been used much but it's of modern vintage.

Answer 1

Diesels not running under load undergo a condition called slobber. Considerable unburned fuel builds up in the engine and turbo. The set should be run at full load at least once a year. Better if you can do it monthly. Most owners test the set weekly without load. This is when the problem begins. The exhaust does not get hot enough to rid itself of the unused fuel. Of course maintenance of the air filter is a must as well.

Answer 2

The answer from Letsee is pretty accurate but I would add that using an injector cleaner ("Tune-Up In A Bottle" made by Lucas is superb, sold at Motaquip stores) added to the fuel will help. My diesel car was smoking quite a bit and after the injector cleaner went in it was a lot better. I subsequently backed off the fuel pump pressure and now the car only smokes slightly when very cold. It is worth high revving the engine once per week to clear out the slobber.

Answer 3

Probably soot building up. You'll need to clean the injectors.

Classic method is to get the motor hot, then run it flat out for a couple of minutes.

If that doesn't cure it, you can get injector cleaning fluids to add to the fuel from most car accessory shops.

If those don't work, check the timing, then after that try replacing the injectors.

To prevent soot build-up in future, mix rapeseed or sunflower oil with your diesel fuel. You need at least 20% veg oil, some diesels are happy on up to 95% veg oil. This is quite legal for a generator as well as cheaper & better for the environment.

Answer 4

Black smoke is normal for a diesel engine.

If you follow a diesel car which is accelerating, you will see black smoke from the exhaust.

It is due to the chemical composition of the diesel, and the method of combustion.

Blue smoke is oil being burnt.

White smoke is unburnt Diesel coming out of the cylinders.

Answer 5

black smoke is always a sign of unburned fuel or hydrocarbons. it happens when the air fuel mixture is to rich or its not properly burning. it could be anything from a slow o2 sensor which is the oxygen sensor on the exhaust telling the computer how much air is coming in and how much fuel to insert or it could be a fuel injector that is leaking or simply dumping too much fuel too soon . i know some diesel engines smoke but some shouldnt smoke as much like in a car. and details on how it runs while sitting or driving ? like does it get rough or is acceleration feel like it hesitates ? any check engine lights?

Answer 6

Just let the engine run and see if it clears ? if not check air filter,
If the generator has been turned on it's side ? it could be that engine oil has run into the valve ports in which case the only thing that you can do is let the engine run and it will slowly burn off ! PS black smoke is engine oil , white smoke is diesel oil !

Answer 7

They call diesels "smokers" for a reason.
You may need to clean the injectors or just let it warm up for a few.
Black smoke is not bad...Blue white smoke is.

Answer 8

Run it on full load for an hour to get up to correct combustion temperature and to clear any deposits.If problem persists check oil level in sump and condition of air filter.
If still smoking check injectors .

Answer 9

if it hasn't been used much it will blow black smoke for a while it is all the carbon that has been in the engine over time it should be fine after a few runs, put it on max load it won't harm it.

Answer 10

Its burning oil. Get it sorted and make sure it's tested on full load