Diesel Engine Failure: What Are the Causes?
Like any complex machinery, many things happen to diesel engines that can cause failure.
What Color Is Your Smoke?
Under most operating conditions, a well-maintained diesel engine operating properly should emit no visible smoke. It's normal to emit a puff of vapor while accelerating under loaded conditions, but otherwise there should be none. If there is, there's a problem that needs to be addressed. Experienced operators are aware that the color of any smoke gives important clues as to what the problem may be, how severe it is and how to fix it.
- Black smoke is the most common type. It is often seen when driving uphill, when the throttle opens to inject more fuel faster than additional air can be introduced to combust it. This means the fuel-rich mixture is being only partially burned. If black smoke is seen only under these conditions, things probably aren't too bad, but if you see black smoke regularly, action needs to be taken.
Other causes of black smoke include poor engine timing, over fueling, poor valve clearances, faulty or dirty fuel injectors, improper fuel/air ratio, poor cylinder compression (worn components) and others. Regardless of the source of the problem, black smoke under normal operating conditions requires a mechanic to replace worn parts, correct the mixture being burned, or to make other adjustments.>
- Blue smoke is a common occurrence upon a cold start. It is an indication that motor oil is entering the engine's combustion chambers. This happens if critical engine parts, assemblies or seals (cylinders, piston rings, gaskets) are worn and permit oil to enter the cylinders. Also, if the oil is too thin for the application, it can penetrate the combustion chambers. Fuel leaked into the oil system also causes it to thin to the point where lubricating qualities are compromised. One thing to watch for is the possibility of burning engine oil without producing blue smoke.
If engine compression is strong, it will burn fuel (and any leaked oil) completely and this will not show up as telltale smoke. If you notice a truck consuming more motor oil than normal without blue smoke, there are probably worn parts that need to be replaced.
- White smoke can mean unburned fuel in your exhaust. If you see white smoke when you cold-start the engine and the smoke disappears as the engine warms, the common cause is fouling deposits on the piston rings. Persistent white smoke could mean something more serious, specifically worn or faulty injectors, poor compression in the engine cylinders, or poor injection timing. This phenomenon is also observed when moisture enters combustion chambers as a result of worn head gaskets or cracked cylinder heads or engine block.
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Helping you "read" the color of your smoke, and suggesting remedies that are economical and beneficial in the long-term, is an important service we provide to owner-operators and fleet managers throughout Ohio, Indiana and Kentucky.
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