A diesel runaway occurs when a diesel engine revs uncontrollably and cannot be shut down. In seconds, this can turn a reliable vehicle into a dangerous machine.
Understanding Diesel Runaway Safety
While modern diesel engines have advanced electronic controls that render runaways the exception, being aware of this problem may just save your engine – and your life. As your professional diesel repair technicians, we’re here to inform you about all things diesel runaways.
Key Safety Information
Knowledge of the causes of these terrifying incidents is important to all diesel engine owners. Knowledge of warning signs can be the difference between a near-miss and a total breakdown. Knowledge of what to do in the fleeting moment when a runaway does happen is equally important in the interest of safety.
Prevention Strategies
Using good prevention methods to protect your engine is the key to long-term safety. Regular maintenance, good inspection procedures, and knowledge of how your engine works can prevent hazardous runaway conditions from arising.
Continue reading to learn more about your diesel engine and what it means for one to “run away”!
What is Diesel Runaway?
A runaway diesel is exactly that – a running engine that will not be shut off even when the ignition is shut off. This hazard occurs when your diesel engine runs independently without your control, normally resulting in severe motor damage to your vehicle or risking you getting injured.
Think of it like your engine going into a feeding frenzy that won’t end. Unlike gasoline engines that require spark plugs to ignite, diesel engines rely on compression ignition. When a runaway occurs, your engine produces a secondary fuel source (typically engine oil) and runs at very high RPMs that are hazardous.
Electronic Control Systems and Safety Features
Modern diesel engines have significantly reduced the risk of runaway situations thanks to sophisticated engineering advances. Electronic Control Units (ECUs) nowadays precisely meter fuel injection, facilitating ideal combustion and preventing excessive fuel conditions. Advanced sensors regularly monitor engine performance in real time and provide feedback information on essential operating conditions. Such technological advances are complemented by systems that automatically shut off the engine once abnormal conditions are sensed so that the engine is turned off prior to a hazardous condition occurring.
Where runaway diesel engines were once standard fare in older mechanical engines, they’re now the exception. Your newer diesel pickup has advanced electronic controls and sensors that monitor engine activity to avoid such unsafe occurrences. These improvements don’t remove the hazard altogether – but they’ve reduced runaway events to exceptions and not the rule.
Causes of Diesel Runaway
Various mechanical problems and environmental factors can cause a diesel runaway. Let’s explore these potential causes:
Mechanical Failures
- Faulty Fuel Pumps: Stuck or malfunctioning pumps can deliver excessive fuel into the system, creating an uncontrolled combustion cycle
- Damaged Fuel Linkages: Incorrectly assembled or broken fuel linkages disrupt the proper metering of fuel flow
- Oil Seal Issues: Failed seals in turbocharged engines allow engine oil to leak into the combustion chamber
- Turbocharger Problems: Leaks in the turbocharger can create a dangerous mixture of unburned fuel and engine oil
Internal Engine Wear
Worn-out piston rings let oil enter the combustion chamber, a precarious condition. When the engine is warm, the oil vaporizes inside the crankcase, exacerbating the situation. The vaporized oil now becomes another source of fuel, forming a self-sustaining process that could be hard to put out. Here, the engine keeps running until it either runs out of oil or crashes catastrophically, and thus, this is a very critical mechanical failure that needs to be corrected at once.
Environmental and System Factors
- Dual Fuel Systems: Engines modified to run on alternative fuels (like propane) face additional risks from improper fuel mixing
- Airborne Vapors: Operating in environments with high concentrations of combustible vapors can feed the runaway condition
- Heat and Operating Conditions: High engine temperatures accelerate oil vaporization, increasing runaway risks
Internal Fuel System Issues
Cracked or broken internal fuel lines are among the most critical weaknesses of diesel engines. When such critical parts break down, fuel leaks into regions it was not intended to go, posing risks. Inadequately tuned fuel delivery systems also enhance such risks by introducing unbalanced patterns of fuel into the combustion cycle. Dirty fuel return lines are also another threat factor since, rather than circulating simply back to the tank, the surplus fuel might find its way to accumulate in the system, producing unsafe operating conditions.
The integration of these characteristics with a lack of proper maintenance is a recipe for disaster. Your engine’s oil becomes an unwanted fuel source, feeding through the turbocharger seals and maintaining the dangerous high-RPM state even after cutting the main fuel supply.
Stopping a Diesel Runaway
Your first impulse would most likely be to shut the key off when handling a runaway diesel engine – but here’s why that will not be effective. Diesel engines, unlike gasoline engines, do not rely on electrical ignition. When a diesel engine has gone into a runaway, it is already consuming engine oil as fuel, so the ignition switch will have no effect.
The most effective way to stop a runaway diesel:
- Cut off the air supply immediately
- Block the turbo intake using a solid, flat object (like a clipboard or metal plate)
- Never use your hands to block the intake
- Remove the intake tube from the turbo if possible
The engine needs air to continue running, so choking its air supply will force it to shut down. While this might seem scary, it’s crucial to act fast to prevent catastrophic engine damage.
A runaway diesel engine running at extremely high RPMs creates a dangerous situation. Your safety comes first – if you can’t safely stop the engine, move away from the vehicle and seek professional help.
Alternative Methods
If you’re faced with a runaway diesel and can’t access the turbo intake, you have two alternative options to regain control of your engine:
1. Manual Transmission Method
- Shift into a higher gear (4th, 5th, or 6th)
- Apply brake pressure
- Release the clutch slowly to reduce engine RPMs
- Warning: This technique can severely damage your transmission and should only be used as a last resort
2. Electronic Air Shut Off Installation
- A preventive safety device that cuts air supply with a switch
- Provides quick, controlled engine shutdown
- Eliminates the need for dangerous manual interventions
- Can be activated from inside the cab
- Ideal for fleet vehicles and commercial trucks
These methods give you additional safety options, but remember – the manual transmission technique risks significant damage to your vehicle. Installing an electronic air shut off system is a smarter, proactive approach to handling potential runaway situations.
Preventive Measures
Regular maintenance is your best defense against diesel engine runaway. Here’s what you need to focus on:
Turbocharger Inspection
Regular turbocharger inspection is crucial for preventing diesel runaway incidents. You need to drain your air intake periodically to inspect the system thoroughly. In inspecting, be careful of the turbine and compressor wheel and inspect for oil contamination. Exercise caution and inspect for excessive buildup or leakage in the entire system. While driving your car on the road, be cautious to observe unusual noises or vibrations that may suggest turbocharger faults.
Maintenance Schedule
Maintenance planning is a must to maintain your diesel engine in the best possible condition. Inspections on your engine should be performed every 3,000 to 5,000 miles to catch issues before they occur. A professional turbo check-up every 15,000 miles for proper examination by trained technicians is advisable. Modify oil and filters at your manufacturer-recommended intervals and follow the manufacturer’s guidelines. Detailed records must be maintained for every maintenance work performed, as this document is used to track the engine service history and detect possible trends or recurring issues.
System Upgrades
Installing preventive equipment can provide added security:
- Fuel shutoff switch – enables quick fuel supply termination
- Electronic air shutoff valve – provides emergency engine shutdown
- Oil catch can – helps reduce oil vapor in the intake system
- Advanced monitoring systems – early warning of potential issues
Turbo Management
Your turbocharger requires special attention:
- Consider rebuilding the turbo at 100,000-150,000 miles
- Replace worn seals to prevent oil leakage
- Upgrade to newer turbo models with improved sealing technology
- Install high-quality aftermarket turbos from reputable manufacturers
Warning Signs
Diesel engine drivers need to be vigilant for a number of key warning indicators that can become runaway conditions. Excessive exhaust smoke is usually one of the earliest indicators of impending failure. When oil consumption starts to rise above normal levels, this will immediately raise doubts about engine conditions. Strange engine noises from the area of the turbocharger need to be immediately investigated by experienced technicians.
Any loss of power or decrease in engine performance that is noticed should never be overlooked, as these may be harbingers of more serious problems. Blue exhaust smoke is especially problematic, as this is usually a sign of oil burning in the engine, something that can become a runaway problem if not addressed.
These preventative actions may appear comprehensive, but they’re but a fraction of the price to repair a runaway engine scenario. A well-cared-for diesel engine with frequent turbo checks and regular rebuilds will offer many years of trouble-free operation and significantly reduce the ability of catastrophic runaway scenarios.
Choose Supreme Truck and Trailer Repair
Your safety in your diesel engine is not worth risking. A runaway engine can turn an engine mechanical issue into a matter of life and death overnight. We’ve left you with the information to identify, react to, and avert these life-threatening conditions.
Don’t wait for warning signs – take action now. Regular maintenance checks and professional inspections are your best defense against diesel runaway. At Supreme Truck Repair, our certified mechanics are here to help protect your investment and ensure your safety on the road.
Ready to protect your diesel engine?
Arrange for a full inspection today to safeguard the diesel engine. Having preventive safety devices installed is imperative for long-term protection. Regular maintenance methods will keep your engine in good condition and prevent possible danger from arising.
Your truck keeps your business moving – let’s keep it running safely. Give us a call today at (403) 603 0274 and schedule your diesel engine maintenance or rebuild today!