Preventing Engine Runaway in Diesel Engines

One of the most dangerous situations that can occur in a diesel engine is "Engine Runaway" or "Diesel Engine Runaway." That's why we at Motor Guide thought to discuss Diesel Engine Runaway in diesel engines today. This is when the engine operates uncontrollably at extreme speed, like it's gone mad. Let's discuss how to prevent this situation.

What is Diesel Engine Runaway?

Normally, a diesel engine is shut down by cutting off the fuel supply. However, when a Diesel Engine Runaway occurs, the engine begins to accelerate uncontrollably by drawing in a different Combustible Material through the Air Intake System, using it as fuel, independent of its own fuel system.

The main contributor to a diesel engine going into Diesel Engine Runaway is Engine Oil leaking into the Combustion Chamber, often through points like Turbocharger Seals or Piston Rings.

Even if the Ignition Key is turned off, the engine continues to run at excessive speeds, eventually leading to a Catastrophic Failure of the engine.

Main Causes of Diesel Engine Runaway

You need to know these causes to focus on prevention.

• Turbocharger Failure:

  A fractured turbo seal (Oil Seals) causing a large amount of engine oil to be drawn through the air intake system is considered the main reason.

• Excessive Engine Wear:

  Oil leaking into the combustion chamber through worn Piston Rings or Cylinder Liners is also a cause.

• Chemical Vapors in the Air:

  Diesel Engine Runaway can occur if the vehicle operates in an environment with Flammable Vapors (e.g., an oil refinery, a chemical plant), and those vapors are drawn into the engine.

• Fuel System Malfunctions:

  Although rare, a malfunction in the Injection System causing an uncontrolled supply of fuel beyond the required amount can lead to Diesel Engine Runaway.

Steps to Take to Prevent Diesel Engine Runaway

The only safest way to prevent Diesel Engine Runaway is to properly maintain the engine before it happens and install emergency protection systems.

Prevention through Maintenance

• Always use the correct type and good quality engine oil and filters.
• If there is any oil leak or abnormal noise from the turbocharger, inspect and repair it immediately. (Blue smoke or excessive oil consumption can be a clue).
• PCV/Crankcase Ventilation system maintenance; ensure that excessive pressure within the crankcase is properly vented.
• Be mindful of the environment. If a diesel engine is used in areas with flammable gases, special safety measures must be followed.

Safety Systems Installation

This is the most effective way to prevent or quickly stop Diesel Engine Runaway.

• Positive Air Shut-off Valve (ASV/PAMS):

  This is an emergency shut-down valve installed within the Air Intake Manifold. If a Diesel Engine Runaway condition occurs, this valve immediately closes, completely cutting off the air (Oxygen) supply to the engine. A diesel engine needs fuel and air (oxygen) to operate. When the fuel cannot be controlled, cutting off the air can stop the engine instantly. These can be activated automatically (when RPM exceeds a limit) or manually.

What to Do if Diesel Engine Runaway Occurs?

If a Runaway occurs, remember that turning off the key will not help. First, stay calm and act immediately.

• For Manual Vehicles:

  Release the clutch, engage a very high gear (4th or 5th gear), and hold the brake pedal firmly. Then, rapidly release the clutch. This attempts to stall the engine by overloading it. This is a last-ditch effort that may damage the gearbox.

• Cut Off Air Supply:

  If you have an Air Shut-off Valve installed, activate it immediately. If such a system is not present, locate the engine's Air Intake Hose and obstruct it firmly and completely. (E.g., take a strong piece of cloth or a blanket and press it tightly against the opening to prevent air from entering the engine). Extreme caution must be taken as this can be very dangerous.

• Evacuate Quickly:

  If none of the above methods succeed, you must move away from the vehicle. The reason is that an engine in Diesel Engine Runaway can eventually explode. In such a situation, being near it could lead to the loss of life.

The most important thing is that even if the engine stops after a Diesel Engine Runaway, it is likely to have sustained major damage. Therefore, it is essential to have a complete inspection performed by a professional mechanic.