Reasons and Treatment of Diesel Engine Runaway
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August 03 11:07:52, 2025
The diesel engine runaway, also known as "coasting," is a dangerous condition where the engine speed exceeds its rated limit, causing violent vibrations, loud noises, and excessive black or blue smoke from the exhaust. This phenomenon not only damages internal engine components but also poses a serious risk to the safety of the operator. It is essential for crew members to recognize and respond promptly to such situations.
Diesel engine runaway can occur due to two main causes: excessive fuel supply or burning oil. Although both scenarios result in uncontrolled engine speed, they differ in symptoms and handling methods. When the issue stems from an over-supply of diesel fuel, the exhaust emits black smoke, and the problem can usually be resolved by cutting off the fuel supply. However, if the engine is running due to burning oil, the exhaust will emit blue smoke, and simply cutting off the fuel may not be enough. In such cases, it's necessary to cut off both air and fuel supplies simultaneously to stop the engine effectively.
Common causes of fuel oversupply include misalignment of the plunger adjustment arm, improper rotation of the fuel pump plunger, worn-out injectors, or issues with the governor mechanism. On the other hand, oil burning can result from excessive oil in the air filter, oil leakage into the cylinder, or faulty piston rings that allow oil to enter the combustion chamber.
When a diesel engine starts to run away, the operator should act quickly. The first step is to close the throttle and shut off the fuel tank valve. Loosening the high-pressure tubing connection and restricting the air intake can help reduce pressure and bring the engine to a safe stop. Specific procedures may vary depending on the engine model, so it's important for operators to understand their equipment thoroughly.
For example, with the 105 series engine, turning the hand crank of the high-pressure pump counterclockwise by about 180 degrees and lifting the lifter can cut off the fuel supply. For the 485 type engine, blocking the intake pipe and disconnecting the fuel line are effective measures. It is crucial not to reduce or remove the load during a runaway, as this could cause a sudden speed increase.
To prevent diesel engine runaway, regular maintenance is key. Avoid adjusting the fuel pump without proper tools or training. Keep all mechanical parts clean and ensure smooth operation. Use the correct grade of fuel and lubricant, and check the governor components before long-term storage. Always follow manufacturer guidelines to maintain the reliability and safety of the engine.