Smoky Diesel engines | Smoking Diesels.

There are many reasons why diesel engines smoke. Here are a few of them. With luck, you will be able to cure your smokey diesel engine!

Smoke from Diesel Engines. Here are some reasons for smoking diesel engines

The exhaust smoke from a smoky diesel engine will tell you what's happening in your engine!

Assuming that your engine is running! The colour and characteristics of the smoke emitted will do much to tell you what either what is wrong with your engine, or what will need attention in the not too distant future!

Most (all) diesel engines emit a little bit of black smoke when accelerating. This is normal. It takes a little time for the engine system to develop the RPM and necessary power to use/burn all the fuel that is being fed to it! This is not a smoky diesel engine. (See How a Diesel works) If there is a ‘lot’ of black – or other coloured – smoke during acceleration, then there is probably something that needs to be put right!

Don’t Panic - Yet!

The first thing to check with a smoky diesel engine is the air filter. If this is dirty or clogged, then insufficient air is being sucked into the system to allow the diesel to burn properly - result = smoking engine.

Take the filter off – it won’t do any harm for a short period of time. Rev up the engine. If the engine still smokes, then it will be something other than the air filter. A pity, because the renewal of the air filter is normally the cheapest option!

The next areas to be checked – by a competent diesel fitter – will be the injectors. (A dodgy injector means low burn quality of the diesel = black smoke) and the engine timing. The latter will cause a general inefficiency of the system, resulting in unburned fuel (black smoking) coming out of the exhaust. It is possible to fix new injectors, but better to get professional help to stop black smoke from Diesel Engine. A professional will almost certainly know from experience about how to stop black smoke from a diesel engine.

After the above, then the engine compressions will have to be tested (By a diesel mechanic). If you have worn cylinders, then there will not be enough compression for complete burning of the diesel fuel. (See How a Diesel Engine Works) It may also be as a result of worn valves – or even valve guides.

If it is the valve guides, then you may see smoke puffing out of the engine crankcase breather pipe.

There are a number of things that can cause white smoke – if it persists after the engine has warmed up. It can be as a result of a faulty injector, timing problems (normal cause), low engine compression, and/or a faulty fuel pump. Air in the fuel system can also cause this problem. This is a rarity, but not impossible.

Lastly steam cause by a head gasket or other water leak into the combustion system can disguise itself as smoke. Steam will dissipate rapidly being once it hits lower temperature ambient air while smoke will persist and hang in the air.

There are other reasons why you can end up with a smokey diesel engine.

If the white smoke is ‘steam’ than it is almost certainly a head gasket blown – allowing water to seep into the engine to get ‘boiled’ or worse – a cracked cylinder head!

If your smoke problem is blue! It is a sign that your engine oil is being burned. If the blue smoke is mainly right after start-up, but then subsides after a warm running of the engine, it is probably worn valve guides. The oil seeps down slowly past the valve guides overnight or whenever, and a little is then ‘available’ for burning in the system! If this is the problem, then the oil will be burned off quickly during start up.

If you see blue smoke constantly when running – and other road users normally point this out politely or otherwise – you probably have a problem with your piston rings, or maybe the cylinders – or maybe both! It will require a major overhaul, involving taking the engine apart. BUT firstly, buy yourself a can of ‘oil treatment’ such as Wynns. This may free up the cylinder rings if left overnight. (May)

Hope this all helps you sort out your smoky - or smoking - diesel engine..

How to Stop Black Smoke from Diesel Engine |