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-   -   Diesel Engine Runaway - What it is, and how to stop it (https://www.team-bhp.com/forum/technical-stuff/204960-diesel-engine-runaway-what-how-stop-2.html)

Great thread and an eye opener. Was not aware of this. I was wondering why not press the clutch and put the car in neutral, engage the parking brake and get out of the vehicle. Let the engine revv and kill itself. The engine will die but at least the vehicle is not dangerous. I am wondering if the clutch is engaged and you loose breaks due to overheating. The vehicle may get uncontrollable.

One of the causes of the Texas City oil refinery explosion was apparently a runaway diesel engine.
A diesel engine will runaway when there is a secondary source of fuel other than the injectors. What has been described so far has been engine oil sucked in to the diesel engine. But if the atmosphere itself has suitable hydrocarbons, and that is sucked in through the air intake, the diesel engine will runaway.

See these links:
https://en.wikipedia.org/wiki/Texas_...nery_explosion
https://www.popularmechanics.com/tec.../a295/1758242/

Nice information Sankar. A few weeks back a Piaggio goods vehicle suffered this in the middle of the road. I believe it has a pretty ancient engine and mechanically governed. The engine revved like mad, there was no visibility on the road due to the smoke emitted, which was mostly white smoke. The engine revved for around five minutes as the driver watched helplessly and it finally seized I guess, since there was all sorts of noise and screeches made. Perhaps a more experienced driver would have done something, especially when the engine of this vehicle is not that complex with electronics and stuff.

Very interesting topic. Would be a disaster if a car would runaway uncontrolled.
In the oil fields, this has happened quite a few times with the engine taking on gas from gas wells and leading to explosions.
Nowadays there is a shut off mechanism on such engines. When the engine starts revving up, beyond a preset value, the fuel and air shut off mechanism would trigger and shut off the engine before a disaster happens.
Regards
Sravan

Many thanks for the information, me being a person who uses an Ambassador (1989 BMC Diesel) as a daily driver.

Many Thanks for such an educative post - I really hadn't even heard of this phenomenon prior to today (though as of now am not a diesel user anyway).

One question came to mind wrt below quote -

Thiis can only happen if the vehicle is stationary; so what can be done for a moving automatic in this case ?

More common on two stroke diesels.

What decompression switch?

Not on our national diesel engine! Look up Shankars thread
https://www.team-bhp.com/forum/techn...ml#post4226520

Regards
Sutripta

The objective is to cool the turbo down. Driving the car at slow speed for a km or for a couple of minutes would be sufficient.

For eg. The turbo in my car kicks in at 1800 RPM. The moment I turn off from the main road into my street, the vehicle speed is low (<20 kmph) and RPM is less than 1800. Once the RPM is below 1800, the turbo beings to cool down. By the time I finish parking the car, I would have already give the turbo ample time to cool.

Didn't the earliest Amby diesel engines come with a decompression lever/switch, instead of the pull switch for diesel pump cutoff? Or am I just confused?

Our old CJ 340 had a knob on the dashboard that had to pulled to shut down the engine.

^^^
Pull to stop cut off the fuel supply. (Which is also why one could also push start a locked Ambassador diesel)! Once started by whatever means, it would continue to run.

CJ340 - strange, this pull to stop.
This was standard on the older diesel jeeps, but by the time the DPs made their appearance, the electrical shut off was standard. The FIP still retained the fuel shutoff lever though.

Regards
Sutripta

Any modern day turbo diesel with a leaky turbo (leaking oil into the engine manifold), will cause a runaway. I have witnessed a Dicor 2.2 runaway like this in my friend's garage. The car had come in for fixing it's leaky turbo, to diagonise the exact area of leak, they fired up the engine and suddenly the car was revving like mad, blelching out white smoke and it ran for a good 5 mins until a mechanic managed to stuff a big rag into the air intake and starve the engine to a stop. The engine was running purely on the oil from the turbo...needless to say, the damage was bent pistons in two cylinders, a fully damaged turbo and some bent shafts.

Well, I have witnessed this not once but twice, IN THE SAME CAR!!!

The car was a 2006 1.9 TDI Skoda Octavia(my dad's car). A runaway diesel engine is something that is pretty much horrifying and any layman won't even understand what is happening. Even if you turn off the ignition and pull out the key, it will keep on revving like crazy.

This was one fateful car. It first got hydrolocked in the rain water. My dad got it repaired at the Skoda ASC (costed around 3 Lakhs in 2008 IIRC) and after that there was like no pick up at all in the engine. Skoda ASC were demanding a couple of more lakhs to change the turbo and some other work. My dad was fed up with them and took it to a workshop specialized in Skoda cars. They changed some valves/seals there and the car was running fine then.

One evening, me and my dad were coming back from somewhere. He parked the car outside the house and I don't remember why but he was revving the car upto 2.5k-3 rpm at idle (Maybe the car had a weak battery at that time and he thought this might charge up the battery) and suddenly all hell broke loose! The car was revving well past the redline, it was like the needle was broken and was resting on the other end of the rev-counter. He turned off the ignition and took out the keys and still the car continued to revv. We got out of the car and ran away from it. We literally felt like it was going to blast or start burning. Well this is a situation which makes you go in full panic mode.

We couldn't see anything around the car. It was like the car was vanished in a cloud of black smoke.Also it was a foggy winter night in Delhi. Luckily the engine was not damaged much and some minor problem in the turbo was diagnosed and it was taken care of...

... No it wasn't taken care of very well. A couple of years later, I got my drivers license. After a few months of getting it, one night I was coming back from the railway station after picking a cousin. I was on a well lit, deserted stretch of road. The stretch was empty with almost not a single vehicle on the road. I was in third gear, I thought about flooring it (The turbo surge of 1.9 TDI was pretty good). The car went 2000 rpm, 2500 rpm, 2800 rpm, 3000 rpm and I pressed the clutch to change the gear and it was all hell broke loose all over again!

Since the road was empty, I managed to pull the car to the side of the road and slammed the brakes. The car was in neutral and the clutch was in the fully pressed position even when I was not pressing it!!

It was exactly the same scenario, thick black smoke engulfing the car. The rev counter was like at 180+ degrees and even after removing the key the car was continuing to revv. After a couple of minutes it shut down by itself. I was around a couple of kms away from home.

I called my dad and told him that it happened again :deadhorse . He said bring the car if it starts by driving it or else get it towed. I sat back in the car, pulled the clutch pedal back out and it was somewhat working okay then. Started the car and it started but something was odd, something was very odd. It was vibrating a bit and felt like it was misfiring. Since it was pretty late at night and it was somewhat a deseted area, dad asked to drive it home if it drives.


This time the engine was gone. It was a miracle that the engine was running in that condition. My dad got it repaired, and still ran it a few years before selling it lol:


PS: Back in 2011, we had booked an Innova instead of Octavia but because due to some issues with the dealer the booking was canceled and Octavia was booked. Well, if the Toyota dealer had not given our Beige car to someone else and not offered us a white car instead, I wouldn't have experienced a runaway diesel engine twice!

Surprised to know that these happen even on modern engines. With so many sensors aboard. Though I haven't experienced one personally or have seen one in person for that matter, I am sure it should be one helluva experience, seeing that motor revving to glory.

What I am surprised by is the fact that you guys got it repaired it back to back spending so much money on the vehicle. Nevertheless, would you say it's built like a tank or is it. ;)

Now, my questions.

Are mileage of the engine factors taken into account for this to happen or can it happen even to a new vehicle, given the wrong circumstances?

Secondly, what is the ONE MOST imminent factor apart from the list of factors that can cause such a displeasure.

Cheers!
VJ :cool:

I don't think mileage played any part in my scenario. When the first time it happened, the odo was at around 55-60k kms, and it happened because the car was hydrolocked a few months earlier and was not repaired properly. The turbo was not working properly after engine was redone at the ASC and then the turbo was repaired at an independent workshop.

Second time also, it was maybe due to the fact that it was getting maintained at an independent workshop. This was a complicated car and I don't think that independent workshops have the proper equipment/expertise to do preventive maintainance as required by the car. But then, as most people know in the automotive community, Skoda ASS was pretty terrifying during those days! (Can't say about what they are upto nowadays)