Diesel Runaway: Causes, Solutions, And Prevention

Published on 08/30/2022

diesel runaway causes solutions and prevention

Diesel engines are ideal for towing and hauling heavy loads. However, a diesel vehicle running on the wrong fuel type can cause significant problems. Knowing the causes, solutions, and how to prevent these problems can help you stay safe.

Diesel runaway, an engine that keeps revving even when off, is a common issue with diesel engines. The engine should stop when you shut off your diesel vehicle’s ignition. An engine that won’t shut off can lead to fire, significant vehicular damage, and potential death or injury. 

Modern and older diesel engines are prone to diesel runaways. Here's an explanation of what to do if you encounter this issue. Additionally, learn about common piston ring failures to prevent other serious problems.

What Is A Diesel Runaway?

A diesel runaway occurs when a diesel engine still operates despite being turned off. Without stopping the fuel or air intake, the RPMs become uncontrollable. 

During a runaway, the engine still receives fuel even while off, and continued air intake results in burning this fuel faster. With continued fuel burning, the engine RPM increases significantly. The engine revs stronger and louder, often prompting black smoke from the exhaust.

Parts may fly from the engine, and crashes are common. This can cause severe damage to the engine itself and everyone around it. 

Causes Of A Diesel Runaway

A diesel runaway has a few different causes. Oil in the intake is the most common issue, while fuel-contaminated air and a stuck accelerator pedal are less frequent causes. Older diesel engines with manual fuel pumps have their own problem where the pump fails and supply the engine with endless fuel, causing runaway.


Oil in the intake

Lubricating oil is a prevalent cause of diesel runaway. While it is necessary to keep internal parts running smoothly, a leak can cause quite a few problems, one of which is runaway.

The turbocharger and crankcase are the two most common culprits that allow oil to reach the fuel intake. Damaged seals make it easy for oil to mix with the air and leak into the engine.

An old crankcase ventilation pipe often has damaged piston rings. Wear and tear here lets oil into the combustion chamber. This issue causes gas to build up and leads to explosions.

Contaminated air

Although possible, it’s less common for contaminated air to cause a runaway engine. Air mixed with natural gas, propane, or other types of fuel a diesel engine can't process can tax the engine, leading to runaway.

Diesel engines are particular, only able to process certain types of fuel. If your engine is around various fuels that it can't handle, runaway is likely.

Diesel Runaway Solutions

Diesel runaway can occur when you’re inside or outside the vehicle, and both situations are equally dangerous. Depending on your specific situation, force may be the fastest way to stop the vehicle. 

It’s crucial to be mindful of other drivers and your surroundings in a runaway situation. Use your best judgment when handling a runaway.

Cut off fuel and air

The fastest way to stop a diesel runaway is to cut off the fuel and air supply. Because diesel engines need these two ingredients to stay running, finding the source of the fuel leak and stopping it is necessary. If you already know the cause, stop the fuel’s flow as safely as possible.

If you cannot stop the fuel and air intake, your best option is to let it burn in a safe location and extinguish the flames with a CO2 extinguisher.

Get off the road

If your runaway occurs while driving, pull over as soon as possible. Slowly remove your foot from the accelerator and apply the brakes. After stopping, get out and contact your local fire department or others who can assist.

Stop the engine

There are various ways to stop the engine. You can spray a fire extinguisher on the intake or throughout the engine to replace the oxygen with carbon dioxide, or physically block the intake with a rag or other object. The goal is to stop the airflow.

It’s not always possible to block the air supply. Damage along the entire intake hose can prevent this. If your vehicle has a manual transmission, you can hold down the brakes, put the vehicle into high gear, and let go of the clutch to cut the engine off.

Preventing Diesel Runaway

Preventing a diesel engine runaway is relatively simple. Routine maintenance and monitoring of the intake hose and turbo are the best ways to keep your vehicle from suddenly developing this dangerous problem.

Schedule regular maintenance

It’s wise to schedule regular maintenance on your vehicle to prevent a diesel runaway. Frequent maintenance can successfully prevent diesel runaways. 

Cracks and other damage in the turbocharger, hose, and crankcase can spread lubricating oil throughout the engine. Because metal parts become worn with time and regular use, you’ll need to monitor and maintain these components to keep them from cracking. Professionals can determine whether your parts need replacing. 

Monitor the turbocharger

The turbocharger is a hotspot for engine-related wear and tear, causing runaway. You should monitor it regularly. Check for physical damage like cracks and splits in the intake hose and contact a mechanic if you notice oil, residue, or other buildup.

Contact Us To Resolve And Prevent A Diesel Runaway

Diesel runaway is an emergency that requires fast, effective, and safe handling. No matter your location in California’s Bay Area, you need an expert diesel vehicle mechanic who can stop runaway and repair the subsequent vehicular damage. 

Without assistance from trained professionals, you face significant difficulty resolving diesel runaway and preventing future episodes. That's why it's crucial to work with a fully-licensed team to keep your engine safe.

A heavy equipment and diesel truck repair company like All Bay Diesel is your leader in mobile vehicular repairs, hydraulics, and more. Contact our friendly diesel experts and get high-quality mobile diesel repair services by All Bay Diesel throughout the Bay Area, CA. Call us at (925) 522-1780.

Call Now: (925) 522-1780