Tech Articles

Smoking Engine

Where there's smoke, there's diesel, you might say. And most smoke is normal. But here are a few guides to help determine if your smoke is a sign of a problem. There are three colours of smoke you can get from a diesel:

1. White smoke means water.
2. Black smoke means fuel.
3. Blue smoke means oil.

A few puffs of white smoke is perfectly normal on start up. On cold days, you may create billows of the stuff, much to the joy of your neighbours if they are diesel lovers. This is largely caused by condensation. But if the smoke continues for more than say 30 seconds at idle, and certainly if it continues once the engine is warm, then you have a problem. Chances are you are running lean. The first thing to check are your filters: make sure your air filter is clean, and try swapping in a new fuel filter. This might be a good time to empty the water seperator too. And check your glow plugs. White smoke may also be an indication of coolant leaking into the engine - a blown head gasket or a cracked head - but if that's the case you should find coolant droppets in the oil and oil in the coolant.

Black smoke is what you see from the big trucks on the road when they start from a stoplight. It's simply unburnt fuel. If you're going up hill and put your foot down, you might make some. But most cruisers don't unless the air/fuel mix is off. If you're seeing black smoke regularly, check your filters, and the govenor diaphram.

Blue smoke means you're burning oil - not diesel oil but engine oil. That's bad.