Diesel Engine Runaway - It is what? What will you do in response?

Diesel engines experience engine runaway more frequently than gasoline engines, which is a dangerous condition. A runaway engine will almost always utterly destroy itself if it is not controlled. If a runaway occurs while you're driving, the car can start to speed on its own, without your asking it to. Understanding runaway and its causes can help you decide how to treat it the best.

Engine runaway: What is it?

Given that you are reading a blog about diesel engines, you probably already know that diesel engines employ compression ignition, or high compression, to start burning diesel fuel. Diesel fuel explodes inside the cylinder due to the intense heat and pressure. Diesel fuel isn't the only fuel that may be used in a diesel engine; in fact, Rudolf Diesel's first diesel engine was intended to run on vegetable oil!

Diesel fuel is the only fuel source entering the cylinder under typical conditions. Yet, since a wide variety of objects can serve as fuel, issues occur when a different source of fuel is present. Engine runaway happens when the engine is using fuel that is not its primary fuel source and is unregulated or unmetered. Engine oil is the most frequent fuel type in engine runaways.

What causes engine runaway?

The engine is constantly burning a little amount of oil since oil vapors are constantly present inside the cylinder, either from the EGR or from leak-by of valve seals or piston rings. The oil content is negligible enough to have no effect on cylinder combustion. Yet, conditions are ideal for runaway when a component of an engine malfunctions and allows extra oil to enter the cylinder.

The turbocharging system nearly usually contributes to excessive oil entering the engine and causing runaway. Although it happens less frequently in small and medium load diesel engines than it does in big industrial motors, runaway can nevertheless happen with severely leaking piston rings or valve seals. The turbocharging system can produce runaway in two different ways:

• Engine oil is used to lubricate the internal parts of the turbocharger. In the event of a turbocharger failure, oil may seep into the engine's intake system. If you think your turbocharger may have failed, stop driving the vehicle right away and have it repaired.
• Engine runaway can also happen with a healthy turbo when there is too much oil in the intercooler or intercooler pipes. This is known as a properly working turbo pushing oil collected in the intercooler system.

Runaway After New Turbocharger: Always drain and clean all intercoolers and hoses before reassembly when repairing a turbocharger or boost issue, including replacing the turbocharger or actuator. If you resolve a boost issue without taking care of those things, any accumulated oil in the system will be forced into the engine, which may result in a runaway.

How can you know whether a runaway is taking place?

In all honesty, experiencing engine runaway is unnerving. Watch some runaway YouTube videos instead of learning about it for the first time in real life. I've put together a playlist of my favorite runaway videos here.

There are two indicators of a runaway condition that stand out right away. The first is engine acceleration, which occurs even when you are not depressing the accelerator pedal. In other words, the engine's RPMs are increasing or the car is speeding. Second, the engine will emit an enormous amount of smoke.

What should you do if you think a runaway is present?

If you are driving the car, there are two principles to follow while dealing with a runaway.

• DON'T TRANSMISSION THE VEHICLE TO NEUTRAL! The engine will accelerate quickly since being in neutral relieves it of load.
• STOP THE ENGINE AND BRING THE CAR TO A COMPLETE STOP USING YOUR BRAKES! Keep the automobile in drive while applying the brakes to slow it down. It should be simple to slow the automobile down using the brakes even while it is in gear because a runaway engine actually produces very little power.

The engine's air source needs to be shut off as soon as you can if you are working on it and it takes off. Suffocating the engine will stop the runaway since combustion can't take place without oxygen. If you work on engines frequently, keep a sturdy object nearby that you can use to block an air intake, such as a piece of plywood (1' x 1'). Blocking the air intake will cause a runaway engine to stop in a matter of seconds.

What harm might result from a runaway not being contained?

A runaway that isn't correctly managed using the methods above will typically be either entirely ruined or require a significant engine repair. A runaway engine will keep speeding up well past its redline until it is physically unable to spin any faster. Engine oil, which typically coats internals like crankshaft and connecting rod bearings, begins to fly off these surfaces when the engine spins more quickly. After there is enough oil discharged, metal-on-metal contact takes place and ADVERSE things happen. The crankshaft's bearing surfaces may sustain damage from a seizure of the engine, or some parts may entirely fail or shear off. It happens frequently that an engine component, commonly a connecting rod, fractures and pierces the cylinder block.

Another possibility is "hydrolocking," which happens when the cylinder is filled with so much liquid, such as engine oil, that the piston is unable to rise to the top of its stroke. The engine will also seize as a result of this.

Now what after a runaway?

The first thing to figure out if your engine had a runaway and it wasn't stopped before the engine seized on its own is why it seized. Usually, it is less expensive to purchase a complete motor than to attempt to fix an engine that has seized due to metal-on-metal contact. However, the damage in a hydrolocked engine is often only a few bent connecting rods. Although it won't be inexpensive, it should be able to repair the engine and get the vehicle back on the road.

Let us know your tale!

Can you recall any runaways? It scared you, right? What time did it occur? Have you had it fixed, and if so, how? Please comment below.