How Does A Diesel Engine Runaway?

Working in or near hazardous environments, such as those found in the Oil & Gas business, exposes you to dangers and risks on a daily basis. Between 2013 and 2017, 489 oil and gas extraction employees were murdered on the job in the United States alone, according to the Occupational Health and Safety Administration (source: https://www.osha.gov/SLTC/oilgaswelldrilling/). The dangerous occurrence known as diesel engine runaway is one of the lesser-known yet lethal threats. Engine runaway is explained in this video from AMOT’s Ask the Expert series.

To comprehend runaway, you must first comprehend the operation of a diesel engine and how it varies from that of a gasoline engine. Spark plugs ignite the fuel and air mixture within the cylinders of a gasoline engine. Combustion in a diesel engine, on the other hand, takes place in a very different way. Clean air is drawn into a combustion chamber by a diesel engine’s intake. The air and fuel mixture in the chamber is squeezed to such a degree that it produces high heat and ignites.

The fuel delivered into the combustion chamber is regulated by a governor, which also controls the engine’s speed. The governor controls how much fuel is allowed into the engine. The more fuel allowed in, the faster the engine will run. A diesel engine can only be turned off by withdrawing the fuel supply or cutting off the air supply.

When a diesel engine ingests a hydrocarbon vapor, or flammable vapor, through the air intake system and uses it as an external fuel source, it is known as a diesel engine runaway. As the engine runs on these vapors, the governor releases less diesel fuel until the vapors are the engine’s sole fuel supply.

It can cause the engine to overspeed, the valves to bounce, and flames to pass through the manifold if not halted promptly. These flames can create catastrophic accidents and casualties by igniting the combustible gases present. The Deepwater Horizon explosion in the Gulf of Mexico on April 20, 2010, is a well-known example of this type of mishap.

Even low concentration levels of gas pushed into the engine intake can cause runaway in 3-12 seconds, giving little time to react. A person’s first instinct when an engine starts to runaway is to turn the key off and stop the engine. Unfortunately, because the engine is now running on combustible fumes entering through the intake, this will not solve the problem. The engine will continue to run wildly, and cutting off the air supply is the only possible alternative at this time.

Thankfully, diesel engine runaway can be avoided. Devices that identify overspeed and shut off the air supply can be put on an engine’s air intake pipe to safely and quickly shut down a diesel engine.

Is diesel runaway a common occurrence?

Diesel engine runaway is a rare event in which a diesel engine absorbs extra fuel from an unanticipated source and overspeeds at higher and higher RPMs, producing up to 10 times the engine’s rated output until it is destroyed by mechanical failure or bearing seize owing to a lack of lubrication.

Can you put a stop to a rogue diesel?

Diesel engine runaway is a risky phenomenon that can be lethal when working in a hazardous environment. When a hydrocarbon vapor is swallowed through a diesel engine’s intake and becomes the engine’s uncontrollable fuel source, engine runaway occurs. When this happens, the governor loses control of the engine’s speed, causing it to speed out of control. If the engine is not stopped, it can suffer irreversible damage or, worse, ignite the fumes and explode. This condition is explained in further detail in our blog regarding diesel engine runaway.

The only proven approach to stop a diesel engine once it has begun to runaway is detailed in this video from AMOT’s Ask the Expert series.

The most usual reaction when an engine starts to runaway is to remove the ignition key and turn off the engine. Unfortunately, this step will be ineffective. Turning off the key will have no effect because the engine is now running on fumes. At this point, the only practical option is to turn off the engine’s air supply. Fortunately, there are safety measures that can cut off the air supply during a runaway situation.

In the event of a runaway situation, these safety mechanisms are known as air intake shut off valves, and they simply block off air entering through the intake. When shutting off the air supply isn’t an option, the engine shuts down since diesel engines work by consuming clean air through the intake.

Depending on the make and type of your engine, multiple systems are available, but they all work on the same principle: once your engine enters a runaway condition, the air intake shut off system will operate, either automatically or manually, and cut off the air entering through the intake. As indicated below, the systems are usually mounted between the engine air filter and the intake manifold.

Now that you understand how an air shut off system works, you should know which diesel engines should have one installed. Diesel engines employed in hazardous situations, such as upstream, midstream, and downstream operations, are all susceptible to diesel engine runaway and should be protected at all times. This comprises both large and small equipment, such as fracturing blenders and coiled tubing units, as well as light towers and generators.

The only established and dependable technique of stopping a diesel engine once it has started to run away is to use an air intake shut off device. Don’t wait until it’s too late to protect your workers and equipment from a calamity that could have been avoided.

Contact AMOT, download our selection guide, or use the filters on our products page if you need assistance choosing the right valve for your engine.

Is it possible for new diesels to go off the rails?

It used to be that a runaway diesel was a fairly typical event. However, since things have evolved, this is now a rare occurrence in modern diesels. Most Electronic Control Modules (ECMs) can more accurately measure fuel, and sensors alert the ECM, allowing it to avoid problems like these. However, everything has an exception, and parts do fail.

So, what creates a diesel runaway condition?

Well, there are a number of factors. Pumps that stick and meter too much fuel, turbocharged engine oil seal failure, overfilling the crankcase, broken/damaged internal fuel pipes, incorrectly assembled or faulty fuel linkages, and even dual fuel engines that use bottled gas (like propane) or are in an environment saturated with airborne vapors are all possible causes. However, aging and wear, as well as vapors, are the most typical causes.

Runaway diesel is particularly noticeable in fleet vehicles that are used frequently, are badly maintained, and are almost always on the road, such as the UPS truck pictured above. However, with one exception that can affect both new and old diesels, age and neglect appear to be the most typical causes of runaway diesel. Because a diesel engine meters the fuel rather than the air, the air flow is fully uncontrolled. If hydrocarbons such as diesel, gasoline, propane, or other airborne pollutants are present in sufficient concentrations, the engine will run uncontrollably till its demise. Due to the extreme heat, the car will occasionally catch fire. So get as far away as you can if you’re going to let it die.

Wear and neglect can also cause the engine to run uncontrolled. In most internal combustion engines, as piston rings deteriorate, a little quantity of oil leaks into the combustion chamber. However, if the wear is high enough and the diesel engine is hot enough, the oil in the crankcase vaporizes and escapes past the piston rings. When the evaporated oil reaches the cylinder and combustion chamber, it behaves like diesel fuel and ignites due to the severe compression. Once this occurs, the engine will continue to run until the oil is depleted or it blows up, whichever comes first.

Is it possible to fix a rogue engine?

If your engine had a runaway and it wasn’t caught before it seized on its own, the first thing to figure out is why it seized.usually It’s cheaper to buy an entire motor than to try to repair an engine that seized due to metal-on-metal contact.In a hydrolocked engine, however, the damage is usually limited to a few bent connecting rods.It won’t be cheap, but it should be possible to fix the engine and get it back on the road.

Is it possible to excessively rev a diesel engine?

There is a maximum RPM for every engine. Though the engine’s maximum RPM can be increased through tuning and other modifications, there will always be a point where the engine can no longer turn faster without causing damage.

The maximum RPM of your engine is ultimately limited by a few variables. These factors include air flow, engine displacement, and piston bore and stroke.

The propulsion that propels engines forward is provided by a series of small explosions. Explosions, like any other fire, require ignition, fuel, and air. Many people install a cold air intake or hood scoop to boost air flow to the engine so that they can gain more propulsion per explosion, however air flow can only be increased so far, and the amount of air available will limit air flow.

Rev limiters are used on modern engines to make it more difficult to damage the engine by over-revving it. Over-revving is only a problem if you’re into old automobiles or like to modify your car to get it to the next level of performance. Older cars can have rev limiters installed, or you can buy ones that can be modified for your new tuned maximum RPM.

The majority of rpm limiters are actually fuel control limiters. They essentially deplete your car’s fuel supply, forcing it to slow down. Spark control limiters are another sort of rev limiter. They work by removing the other component required for combustion: the spark. The issue with spark control limiters is that fuel is still pumped into your engine’s cylinder; it simply isn’t burned. That fuel will still wind up somewhere, and where it will end up is a whole other delightful issue you’ll have to deal with if your engine decides to slow down.

Unfortunately, whether or not you have a rev restriction placed, if you have a manual transmission vehicle and it shifts poorly, it makes no difference. Cutting power won’t necessarily prevent your engine from spinning significantly faster than its permissible range if you’re downshifting early. Over-revving occurs most often as a result of missing a gear during shifting, rather than as a purposeful attempt to push a vehicle.

A rev limiter in a manual car will not be able to react quickly enough to prevent the engine from over-revving if it downshifts accidentally. This is known as a mechanical over-rev, and while it’s simply a temporary blunder, it can have long-term engine damage.

The sound is usually the first thing that people notice. As soon as the car is placed into an uncomfortably high RPM, it will produce a terrifying sound. This sound serves as a warning siren, alerting you to the fact that something is badly wrong.

If you’re driving a manual transmission automobile and realize you’ve under-shifted, the easiest approach to avoid over-revving is to slam the clutch foot in. In a manual car, depressing the clutch prevents the wheels from being connected to the engine.

When we talk about engines in “litres,” we’re talking about the entire volume of the engine’s cylinders. The displacement of the engine eventually becomes a limiting factor in maximum RPM. Torque and power increase as displacement increases.

The pistons must pass through four stages: induction, compression, combustion, and exhaust, all of which take time. Although the amount of time it takes is minor, it does become a limiting factor.

Even in the few seconds it takes to realize you wanted to shift to fourth gear but landed up in second, over-revving can cause major damage to your engine. The good news and bad news is that you’ll know almost immediately if you’ve significantly damaged something.

Over-revving can damage your valve train by allowing a valve to stay open for an extended period of time, resulting in valve float. When a valve floats between open and closed, it is known as valve float. There will be an instant loss of electricity as a result of this. Valve float is the only one of these issues that can go unnoticed for a long time before causing trouble. At greater speeds, you’ll be able to discern if the engine is misfiring or losing power. Simply replace the springs to fix valve float, which is a nice thing to do anyway as part of routine maintenance.

The most common cause of catastrophic engine failure is a connecting rod failure. The connecting rod is a metal element that links your piston to your crankshaft and resembles a wrench. It is necessary for the vehicle’s operation, but it isn’t why it causes catastrophic engine failure. Connecting rods are found in the heart of an internal combustion engine’s magic.

With the pistons and cylinders above and the crankshaft below, the connecting rod is a solid piece of metal. Whatever direction you throw your connecting rod, it’ll throw a lot of essential stuff out with it, and it’ll throw your engine out of rhythm. The only reason your automobile isn’t destroyed by the millions of small explosions that occur in your engine is because of a perfectly timed series of operations that contain and utilize every ounce of power generated by those explosions.

However, if one element of choreography fails, the entire routine can be undone in a matter of seconds.

This makes the most sense out of all the problems that over-revving might bring. Your clutch is what connects your car’s wheels to its engine. When the RPMs are much higher than the safe maximum output, it is this section of the car that will suffer the most immediate damage.

Friction is the sole thing that makes the clutch operate, but too much friction generates a lot of heat and tension between the clutch plate and the flywheel.

We recommend that if you suspect a problem, you have it checked out by a specialist.

Is black smoke harmful to a diesel engine?

Diesel engines are known for being filthy and producing a lot of black smoke. One of the most common images is of a diesel rig speeding down the highway, black smoke billowing from the stacks. That was pretty much viewed as normal in the 1960s, 1970s, and 1980s. All of this is unfortunate, because a diesel engine is more efficient and reliable than a gasoline engine.

The modern common-rail diesel engines are a significant improvement over older diesel engines, allowing for significant increases in horsepower and performance without producing a lot of black smoke.

The corollary to this is that if your diesel emits black smoke, it means something is wrong and needs to be corrected.

Not only does it make you look ugly, but it’s also bad for the environment, and it’ll cost you more in the long run because black smoke implies lower fuel mileage and more money out of your wallet. So, let’s look at what produces black smoke in diesel engines to see how we might lessen it.

Restricted Air

Fuel that hasn’t completely burned is seen as black smoke. When a diesel engine is working properly, it will totally burn the fuel, producing CO2 and water. As a result, black smoke indicates that something is preventing the fuel from totally burning. The proper amount of air is required to completely burn the fuel, which is a vital component of the combustion process. Incomplete fuel combustion results from a lack of air.

What may be the source of this suffocating air? It could be due to a clogged or limited air cleaner system.

Turbocharger Lag = Puffs of Black Smoke

When large diesels with huge loads are about to accelerate from a standstill, they often puff black smoke. This enormous diesel has massive turbochargers that require a long time and a lot of fuel to get up and running “Spool it up.” They’ll do this while they’re waiting for the ball to start rolling “Before the light turns green, they “roll coal,” trying to get the turbocharger up to speed before they move. This consumes a lot of gasoline in an engine that runs at low RPMs.

This problem occurs primarily in older trucks and is a design flaw. There isn’t much that can be done about it besides perhaps adding a combustion catalyst to the fuel to increase the amount of diesel burned at low RPMs.

Incorrect fuel/air ratio or injector problems

Black smoke is produced when a mechanical issue breaks the equilibrium between the proper quantity of fuel and the right amount of air being burned. It could be as simple as tweaking injector timing or inspecting the EGR system to ensure the EGR valve does not require replacement.

If it’s not like that, you’re dealing with a mechanical issue. It’s possible that the valve clearances are incorrect. Alternatively, the injectors may need to be examined. The most important component of a well-running diesel engine is the fuel injectors. You won’t receive the finest atomization of the fuel if they’re worn or plugged, which is what the engine relies on for its optimal performance.

Engine Deposits Will Cause Black Smoke

When a car is brand new, it performs at its best. Engine conditions deteriorate over time, resulting in accumulations of combustion product combustion in important regions such as injectors and combustion chambers. And all of this gets in the way of optimal performance.

Diesel engines are particularly susceptible to this since a) they operate for such a long time and b) diesel fuel does not arrive from the refinery with any detergent packets already added.

The solution is to regularly add a detergent addition to your diesel fuel. Dee-Zol is a multipurpose treatment that cleans up deposits, reduces the quantity of fuel consumed inefficiently, and can even extend the life of your DPF (because less soot are being produced at any one time).

Why do diesel engines make a banging noise?

What causes diesel engines to make a clatter that is not audible in gasoline engines? P.S.

The clatter is caused by the engine’s internal burning of diesel fuel. Rather than a spark plug, the fuel in a diesel engine is ignited by high pressure and temperature inside the cylinder.

The clatter is caused by the fuel not burning evenly like it would in a gasoline engine, resulting in a knock. Unlike in a gasoline engine, knock in a diesel engine does not usually pose a threat to the engine. It is simply offensive to the general public.

Because the diesel engine lacks a spark plug and relies solely on the compressive heat inside the cylinder to ignite, the fuel must have excellent ignition characteristics. However, strong ignition quality in any fuel is not always accompanied by good anti-knock capacity. Diesel fuel has a low anti-knock capability since it requires a high igniting capability.

Q: You published a list of the most often stolen autos a long time ago. I was hoping you could provide me with some more updated information. I’m replacing a stolen vehicle because I don’t want it to happen again. T.M.

How do you bring a rogue engine to a halt?

Under no circumstances could the engine take precedence over your own life (or others). Allow the engine to scream like a demon, shift into neutral so it won’t accelerate any more, and pull over. If you drive an automatic, don’t worry; most of them allow you to pick neutral and stop while driving.

When I turn off my diesel engine, why does it continue to run?

You’ll hear your engine burning or coughing if it continues to run after being turned off. Because combustion of the air-fuel combination occurs without the presence of a spark, similar to a diesel engine, this state is also known as after-running or dieseling. The pistons continue to travel up and down the cylinders for a few seconds. These symptoms are typically caused by a malfunction that raises the temperature in the combustion chamber(s).