Read Those Marine Diesel Engine Smoke Signals

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Read Those Marine Diesel Engine Smoke Signals

Diesel engine maintenance is pertinent for functioning. Even a small problem can cause irreversible damage to the engine.

Overheating, overloading or problems with other parts are indicated by particular signs. Smokes, of various hues, are one such sign.

Smoke can alert you to a problem with the diesel engine. It can also be indicative of future problems. Typically, blue, black and white smoke is observed.

Let’s learn a bit about these smoke signals so you can gauge a possible cause.

Blue smoke

Blue smoke usually appears upon burning of crankcase oil in the combustion chamber of the engine. It can potentially cause carbon buildup in the chamber.

Worn valve stems (thin shafts on intake and exhaust valves) and guides (tubes in which stems move) can allow oil to sneak past and mix with the fuel. Since oil is heavier than diesel, it doesn’t completely burn. This results in blue smoke and carbon formation.

The culprit could either be stems and guides or piston rings. Cylinder differential leak-down test can help determine the actual problem. A diesel mechanic can perform this procedure. Keep in mind that the test requires compressed air.


Black smoke

This is an indication of partially burned fuel oil. One of the causes can be overloading. It is also called overfueling as more fuel than what can possibly burn is filled in the engine. This can occur while docking if the engine is gunned for a moment, resulting in black smoke.

If black smoke constantly emits when running under heavy load or even under ordinary speed, it is a sign of chronic overfueling. This can happen if a propeller has too much pitch or has a great diameter.

Fouled prop, worn out or malfunctioning injectors, and wet or clogged air filters can also cause the same problem.

White smoke

A number of factors can result in white smoke. Most often, it is a result of one of these:

Overcooling: Cylinder head as well as combustion chambers operate at a lower temperature than required for proper combustion.

Piston-ring blowby: It indicates low compression and reduced combustion.

When cold engine is started, it is normal to see small droplets of fuel resulting in a fogged appearance. However, this is only visible until the engine heats up. However, it can result in excessive white smoke production if an air-intake heater or glow plugs are malfunctioning. It might be long lasting and make it impossible to start the engine.

Low quality fuel, especially the one formulated as Number 2 diesel burns poorly, also resulting in a white smoke. A fuel cetane booster can potentially alleviate this temporarily and thus help identify this problem.

Worn or poorly adjusted valves, blown head gasket, partially activated decompression lever and cracked cylinder liner or head can also be a factor.

Overheating can cause white smoke, which is actually steam coming from exhaust system. Measuring water temperature of exhaust hose can help you test this.

If you find that one or more parts are malfunctioning, resulting in any of these types of smoke, we recommend changing them immediately. Delays can further exaggerate this problem. Changrun trade is a marine engine spare parts supplier, offering high quality ship engine parts. Contact us today to get replacements.

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