SAFETY!!! Couldn't turn tractor Off! Anyone experience this?

[EE_Bota]

Wow! What an experience. These are very interesting stories and a new world for a "gasoline engine type of guy - like me!"
I recently bought a bx25 so I am very interested in these diesel engine stories.
A gas engine that ran at full throttle, with no load on it, would self destruct. I can't believe these diesels can do that and not be damaged.

Good...don't believe it.
If you are new to diesels, don't take any instruction from an improperly running out of control diesel. That diesel was getting it's fuel from a different source than is normal, and it was likely a 2 cycle diesel too. The poster will have to speak to that, but frequently detroits on a boat are 2 cycle so in the case of two props, they can run in opposite directions.

There is a good chance that the engine was being governed to a very low speed as it was running away, and was getting it fuel from a mixture of lube oil and diesel, directly from the blowby gasses. That is not normal, and don't base your new understandings of diesels on that scenario.

 

[jgheck]

Wow! What an experience. These are very interesting stories and a new world for a "gasoline engine type of guy - like me!"
I recently bought a bx25 so I am very interested in these diesel engine stories.
A gas engine that ran at full throttle, with no load on it, would self destruct. I can't believe these diesels can do that and not be damaged.

Hello Homeputter, Let me clarify a little of what the condition was. If you read the entire thread it probably will make more sense. The BX 25 is a 4 cycle diesel. Not as EE_Bota mentioned. It is not a 2 cycle, it also was not getting its fuel from a different source. He apparently has not read the entire thread as this was explained. I only posted all this to help others that may run into this problem. The 20 amp fuse had blown and this would not allow the tractor to shut down by turning the key off. It was not running at full throttle either. But I had it up on blocks and had been working on it. I started it as usual but could not turn it off. If you read the entire thread all of this was explained. I ended up pulling off the air inlet to the engine and put my hand over it to shut it down. Even disconnecting the battery would not turn it off. I since have put an emergency shut off on it. Just in case it would ever happen again. I hope this helps. I learned an awful lot about this tractor working on it. I too have read as much as I could find on this forum about the BX 23. It is a good tractor and is now running well.

 

[Max Power]

Wow! What an experience. These are very interesting stories and a new world for a "gasoline engine type of guy - like me!"
I recently bought a bx25 so I am very interested in these diesel engine stories.
A gas engine that ran at full throttle, with no load on it, would self destruct. I can't believe these diesels can do that and not be damaged.

most gasoline engines are not governed (industrial and utility gas engines are ..like lawn mowers and standby generators) that is why a car engine will destruct if it is put to full throttle.

diesels are almost always governed to a top RPM

the run-away diesel engine is an anomaly, it is very rare and also can exceed it's governed speed because the engine's fuel system is out of the picture and there is no governing of the engine.

 

[JoeL4330]

The emergency shutoff you installed shuts off the (normal) fuel delivery but as others have pointed out diesels can be fueled by other routes, and the only sure kill is to smother it...as you did;

Google "runaway diesel" and you find out all you could want to know and more.

Emergency shutoffs, when installed to stop runaway dieseling, are plates that occlude the air intake ...and, they may only be good for a few emergency stops before the baffling plate is bent and ineffective.

Want to install a real emergency shutoff? check out:

air intake shut off valve by amot control - emergency shut down valve

for example

 

[Max Power]

Good...don't believe it.
If you are new to diesels, don't take any instruction from an improperly running out of control diesel. That diesel was getting it's fuel from a different source than is normal, and it was likely a 2 cycle diesel too. The poster will have to speak to that, but frequently detroits on a boat are 2 cycle so in the case of two props, they can run in opposite directions.

There is a good chance that the engine was being governed to a very low speed as it was running away, and was getting it fuel from a mixture of lube oil and diesel, directly from the blowby gasses. That is not normal, and don't base your new understandings of diesels on that scenario.

4 cycle diesels can run away as well as 2 cycle ...the detroit diesel 2 cycle was more apt to run away then other types of diesels (many industrial applications had emergency shutdown systems that would drop a plate across the air inlet.) ...also it will not usually run away when at low speed ..they usually run away when operated at high speeds (RPMs)

..and the 2 cycle wasn't designed to be a boat engine per se.

the 2 cycle Detroit Diesel was the only engine in locomotives and highway buses for many years in north america.

 

[keyman1808]

I may be mistaken but isn't the BX25 a 3 cylinder diesel??

 

[Max Power]

I may be mistaken but isn't the BX25 a 3 cylinder diesel??

yes ...three cylinder ...4 cycle

 

[keyman1808]

My bad I didn't have my glasses on....duh

 

[CT Jay]

I haven't tried this, because my BX25 hasn't had a runaway engine (yet!)...but I have a feeling that if you completely obstruct the exhaust, the engine will quit.

I'm thinking that a heavy towel or cloth stuffed into the exhaust pipe, or a heavy insulated glove held firmly over the exhaust pipe will choke off the engine.

I used to fly radio control planes, and occasionally someone would have an engine that wouldn't shut off because of a control servo problem that wouldn't close the throttle. The standard quick way of stopping the engine was to put a finger over the carburetor air intake....but a lot of guys, including me, were nervous about sticking a finger that close to a spinning propellor.......I can tell you from my own experience that even a model airplane prop can do serious damage.....I have a bunch of scars on my left forefinger from an accident where I got in the way of an idling prop....needed a bunch of stitches at the emergency room.

So, the safer alternative was to block the exhaust at the muffler outlet. A rag did the trick. Engine would quit in seconds.

Now, of course, we're talking about a 2 or 4 cycle glow engine, with about 1/1000th the power of my 3 cyl Kubota diesel....but I have a feeling the principle is the same, and this would work, as long as I didn't burn my hand on hot exhaust while doing this.

My son once had the tailpipe of his car stuffed with snow that then iced over....completely blocked the exhaust system. He couldn't start the engine, until he finally figured out that he had a tailpipe full of solid ice from having backed into a snow pile the day before while parking his car, which then froze solid overnight.

Personally, I'd rather choke off the exhaust on my tractor, with the pipe right out there in the open, than mess around under the hood with the engine running, taking off the air cleaner and choking off the air supply.

Anyone have any experience with this? Or is this a dumb idea and I'm not seeing why it is?

 

[aczlan]

most gasoline engines are not governed (industrial and utility gas engines are ..like lawn mowers and standby generators) that is why a car engine will destruct if it is put to full throttle.

Actually, many cars (all Volvos with EFI) DO have a rev limiter in the fuel injection "brain".
If you hold the gas pedal to the floor on a Volvo 940, you can bounce the engine against the rev limiter all day long. When it hits the rev limiter, it stops feeding fuel until the RPMs drop to below the limit.

Aaron Z