I found this watching YouTube yesterday, and I didn’t know absolutely anything about it. It’s pretty scary if you ask me. You can watch an example here: https://youtube.com/shorts/8z4M6dhMZt0?feature=share

Diesel runaways are an extremely rare engine fault in turbodiesel engines. It can happen in any vehicle with this engine: cars, vans, trucks, semis, buses…etc. Diesel runaways are caracteristic for the white and dense smoke coming out, but specially for the high pitched sound they produce.

Reason

These are produced by an oil leak in any main part of the engine (usually the turbo), causing to enter the cylinders and burn mixed with the diesel and air. Even if you try to turn the engine off, it just won’t, because as diesel engines don’t need a spark to work, the engine will keep running on oil. On the start of the runaway, the engine will quickly rev up on it’s own until it reaches its physical limit.

What to and not to do

If you don’t try to stop it, it’ll be just a matter of minutes for the engine to seize, blow up, or who knows. These are some things that are useful to stop the engine:

• Blocking the intake with a shirt (or any other clothing)
• Spraying the intake with a CO2 extinguisher (if you have one)
• Trying to stall the engine by engaging the highest gear and/or emergency brake, then releasing the clutch

On the other hand, these are completely useless:

• Taking the battery out
• Trying to turn the engine off using the ignition switch
• Spraying the exhaust with an extinguisher (I’ve seen people do this)

If you happen to experience this (which I hope you don’t), it’s very important to not try to turn the engine on again, as the runaway will happen once again. The correct thing to do is call 911 to get your car picked up.