Runaway diesel

[Captain Larry-DH]

I stumbled on this YouTube video tonight and I suspect it‘s a “runaway“ diesel. For those who don’t know that’s when an engine starts to run on its own internal crankcase oil and the only way to shut it down is to shut off the air supply.
My engines air intakes would be pretty easy to block off with a cutting board but it would take at least 2 or 3 minutes to
1- recognize and understand the situation
2- grab the cutting board
3- climb down into the engine compartment and block the air.
I’m now convinced after seeing the speed and violence of this engine explosion that I need a remote way to kill the air supply in case this ever happens, OR I continue under the assumption the odds are extremely low in a properly maintained engine and if it ever happens just let it blow and deal with the aftermath (fire and damage). There’s no way I’d climb down into the engine compartment if it’s revving like a banshee. I don’t want any close encounters with flying metal.
If I’m wrong and this isn't typical of what happens with a runaway diesel please set me straight
Runaway diesel explodes

 

[garymalmgren]

If I’m wrong and this isn't typical of what happens with a runaway diesel please set me straight

You are wrong and this is not a typical runaway diesel!

 

[Hayden Watson]

If I’m wrong and this isn't typical of what happens with a runaway diesel please set me straight

You are wrong and this is not a typical runaway diesel!

I agree, that is not a runaway diesel. In a runaway, the engine will rev in a series of surges like you are punching the throttle and then letting it spool up and back down. What it is doing is burning the oil that leaks past the rings, and it actually makes very little torque. This truck was on a dyno and they were going for max horsepower output and something let loose inside.

 

[Captain Larry-DH]

Ok thanks gentlemen. Reassuring to know. Startling video.

 

[jackhart]

Unless your engine has a turbocharger, you shouldn't have to worry about it.
The turbocharger is burning the oil.

 

[colemj]

There is a situation where the engine can runaway at full bore and cause catastrophic damage. That is when the fuel pump diaphragm splits and dumps fuel into the oilpan, which easily goes past the rings into the cylinders. The entire crankcase will fill with fuel and thinned oil. It won't explode like that video, but it will likely end up with a cracked block or thrown rod or other catastrophic event.

It won't be slow surging like when bad oil rings let oil burn, and it has nothing to do with a turbocharger unless its oil seal fails and dumps oil into the air intake. Turbos don't burn anything themselves.

Mark

 

[Alan Gomes]

There is a situation where the engine can runaway at full bore and cause catastrophic damage. That is when the fuel pump diaphragm splits and dumps fuel into the oilpan, which easily goes past the rings into the cylinders. The entire crankcase will fill with fuel and thinned oil. It won't explode like that video, but it will likely end up with a cracked block or thrown rod or other catastrophic event.

Which is one of a few reasons I bypassed the on-engine mechanical diaphragm pump on my Yanmar 1GM and replaced it with a Facet electric fuel pump. (The other and main reason was so that I could modify the fuel plumbing to make priming the engine a breeze through the flick of a switch in the engine compartment.)

 

[Ralph Johnstone]

I may be missing something here but how does a boat's diesel engine manage to run away if it remains in gear ? A reasonably propped engine will be pretty much tapped out at 3,600 to 4,000 RPM and supplying more fuel by engine mishap will only lead to smoke. Not one iota more power. The engine will smoke because it needs a higher RPM for more combustion air.

To me, it's always appeared that somehow the engine is placed in neutral before the runaway begins. If my engine appeared to be taking control away from me, the last thing I would do is to shift into neutral. My first choice would be to make sure I had enough room to come to some decisions before hitting something.

 

[Urban Hermit]

Governor failure, at the point when it puffed black, stopped smoking, and increased RPMs?

 

[dlochner]

To me, it's always appeared that somehow the engine is placed in neutral before the runaway begins. If my engine appeared to be taking control away from me, the last thing I would do is to shift into neutral. My first choice would be to make sure I had enough room to come to some decisions before hitting something.

Sometimes you don't have that choice. I haven't had a runaway diesel, but I did lose control of the transmission while in gear in a narrow fairway with lots of expensive (think Hinkley) boats around me.

 

[Urban Hermit]

Had an old Grand Banks woody. Transmission cable came loose. Rammed a dock. Embarrassing but both dock and woody were stout enough to escape damage.

 

[Robert Strickland]

I agree, that is not a runaway diesel. In a runaway, the engine will rev in a series of surges like you are punching the throttle and then letting it spool up and back down. What it is doing is burning the oil that leaks past the rings, and it actually makes very little torque. This truck was on a dyno and they were going for max horsepower output and something let loose inside.

I agree with some but not all here.
It's a solid response, but in my case, there was no pulsing or series of surges.

It happened to me, I didn't recognize it for what it was and tried throttle, pulled cables (troubleshooting) and stuck the palm of my hand over the air intake and slowed it to near stop and realized I could control it to not stall. I asked (Probably yelled and sounded urgent) my wife to jam it in gear and it stayed revving more reasonably.

Once I realized we weren't over revving to blow something, my goal was to get us nearer shore before bailing out then in 12 or 15 minutes, we were within reach of the marina and I parked it with a pretty good bump on the dock.

Points to note;
1. Yanmar 2qm15 - in hindsite probably safe enough to snuff out with palm of hand - bigger engines I think cold hurt you with ait intake?
2. No pulsing in my case, but later found 1 connecting rod snapped so it was running, run away on one of 2 cylendars, maybe different cause could have the pulsing?
3. Agreeing with above, I think (a) I was trying to shut engine down with restricted air but once I got some comfort and wife put it in gear... I believe there was very little torque. Probably running on one cylendar, with quesiotnable rings?
4. That video is more like a 300 or 400 horsepower engine and intentionally held to high rev's
Maybe others have experience with runaway on engines between my expiernce (15 horse Yamar) and that truck in the video?

 

[colemj]

If the cause is fuel dumped into the sump, this usually manifests itself at the next startup after fuel has accumulated and the rings have cooled, and not underway while in use. Even in use, what good is an engine running uncontrollably at "only" 4000rpm? You still need to stop it either way, and prolonged running at WOT or greater will harm most small auxiliary engines. So the only practical difference between a runaway engine limited to prop delivery and one in neutral is the relative safety of getting to it to shut off its air supply.

Mark

 

[Urban Hermit]

That, methinks, was a lot more than an engine pushing a rod through the block or blowing off a head. That had to be a lot of pressurized fuel vapor lighting off. Whatever the malfunction I'd bet a crankcase explosion.

 

[garymalmgren]

The original video is a gasoline engine being pushed over specified operating limits.
It is on a dynometer to measure the engine performance.( horsepower. revs. torque)
Something went wrong and it disintegrated. Or maybe for clicks the "influencers" wanted this result.

In any case it has nothing to do with a diesel engine run away.
Especially, a small marine diesel engine!

Gary