Runaway Diesel???

[BIGDIG]

Last night an excavator in our tunnel started to rev high. The operator wasn't touching the controls,just sitting,idleing. . It started to shoot soot and black smoke ... He couln't shut it down. He even tried to choke out the air intake,but then it went WEEEEEEEEEEEEEEEEEEEOo. Maxed out RPMs and the soot/smoke filled the tunnel. Up we all went in the cage,leaving the machine running,along with us . The shaft disapeared in the smoke,then up it came,covering our site like the London Fog. Then the machine stopped and idled back to normal. . Fire Dept arrives looking for The High Rise Building Fire... . . So what causes a RUNAWAY DIESEL anyways. .

 

[bighammer]

A leak in the turbo can cause the engine to use its own lube oil as fuel. Even though you don't give any throttle, it will run like crazy until the lack of oil in the crankcase catches up.

 

[lmills]

Not, sure, but I have heard that it can come from a seal in the turbo leaking oil. The oil is then burned even though the injectors aren't feeding the motor causing it to run away.

 

[lmills]

bighammer beat me to the punch

 

[BIGDIG]

Ok,but the machine idled back down and stayed running,ran for about 30mins before I gave the ok to go back in. Then the oper went in and shut it down. the lube oil was still at an ok level though. . and it's been running for almost 24 hours non-stop since then. . I dunno??

 

[RustyJC]

Any combustible fuel pulled into the air inlet can cause a runaway diesel. Could there have been a methane pocket?



Rusty

 

[BIGDIG]

Not likely..... But it was next to a Port-a-Poti:-laf

 

[R.E. Miller]

What engine was it? It is unusual for an engine to runaway from idle unless it had picked up a gas like stated above, our fuel/oil went directally into the intake. The Hazmat guys that come to our work to vac out bad gas, diesel, oil, or whatever, use an exhaust extention on the pump on their trucks because the trucks engine can at times... . catch a wiff And sceptical me actually got to witness that, pto was set at 1200, with a celect plus cummins engine, you are going to sit at 1200 if you ask for it. The guy was pumping out gasoline, and at times you could hear the engine just sniff in the free HP in the air... . yikes



If the engine was mechnical, and was an old pt pump cummins like the 855 or l-10, you might be able to make it do that a little if some how the AFC got air on it, or if there was an all-of-the-sudden restriction in the return line (neither likely) I wonder if the unit has air controls... ..... Wait a minute, brain fart, there is a unique engine speed control that was used on the old PT pump engines that used air to run a valve that jacked-up pump pressure to raise engine speed for extened idle/PTO operations. I was working on a bus that had one, they capped off the return line on the engine speed control, which caused a huge back-up, that allowed max fuel pressure at any throttle posistion Real scary, insane RPM's, tons of smoke, but IMHO if that went wrong on that excavator, it would have locked-up in less than 10 seconds.



Sorry for the chatter,

Russell

 

[Ncostello]

On rare occasions... when winds change or drivers dont position trucks right... fire trucks can suffer this. Black thick smoke from a building fire can be very rich in carbon and other combustible materials. Its just waiting for an ignition source to flash or burn. More likely is when firetrucks are positioned too close to gas leaks. They make intake valves to shut down runaway diesels. I've never seen it personally but have read about it. Wonder if by some strange occurance the smoke from the exhaust was at just the right mixture to cause this? Then finally it ran out of enough oxygen to support the combustion which killed the engine. Just a theory among other things possible.

 

[MPBerk]

There is two different ways to describe what you experienced. What you stated is what we in the Naval Engineering world call a "over-speed", going to or above the max no load rpm and staying steady at a given rpm. Second, is a "runaway", Thus burning oil thru turbo, blower and any oil it can find to sustain combustion. The engine rpm continues to rise, rise, rise until the it suffers a catastrophic failure. . or the "BIG BANG".



Most i have experience are from earlier model engines using mechanical or hyd/mech governing mechanisms and mechanical fueling arms "The Rack". It becomes stuck in full fuel position and the gov flyweights respond accordingly, but cannot bring the rpm back down. Over-speeds were common on Cummins 1710/903 series with a PT/PTG (Pressure Timed Gov) assy. Know of a few on 53/71/92 series Detroits and one of a CAT 3412 (over-speed). Most were controlled by a electrical/mech solenoid as an overspeed trip at a given rpm above normal. Since the evolution of the electronics (ECM controllers) such as DDEC iii/iv, they occur few and far between.



If its a runaway you will know it when it happens, scare the poop out of the biggest man. Only seen one and never want to see another. Best to control both is secure the fuel supply and place a plastic bag over the air intake and wait/pray. If it won't stop, if possible keep a load on the engine, NEVER place it neutral or equiv. NEVER EVER shoot CO2 into the intake..... hot internal components+ immediate sub-0 temp =you get the picture. Avoid positioning yourself @ the side of the cyl block ( be at the front or flywheel end, much safer.



Now that I have bored you. . hope it helps you understand what happened.



Mark

 

[Philip]

place a plastic bag over the air intake

Won't work most of the time. Not enough material thickness. A run away would suck it in with no problem. I have seen a runaway 6-71 Detroit suck a field jacket out of a guy's hands and inhale it. The engine didn't die till parts of the coat went out the muffler. Talk about a mess. LOL " It was not me that did the coat trick either".



A good solid piece of board is the best thing. I recommend anyone with a Detroit to install the factory made air shut off above the supercharger.





I don't know what caused that problem BigDig. But that runaway is something you will not forget the sound of.

 

[illflem]

The newer JD excavators I've run have a fuel saving system that returns the engine to idle when it isn't working then returns to full throttle the instant you touch a control.

Wonder if something may have messed up with this system way overfueling it?

 

[BIGDIG]

Should have posted the type of machine. .

German made--LEBHERR 900 tunnel excavator. Runs fine now. Thanks for all the replies,

 

[EMD Diesel Power]

sounds like you had an fuel sucked into the intake. (black smoke and soot) Many situations have been discussed already. I have seen locomotives idle up a bit if they suck in fuel-rich exhausts from other cold-started units.



An turbo oil leak runaway generally will destroy the engine in seconds if you can't keep the RPMs down.



As for the old Detroits... . I've heard stories where the Madison (WI) phonebooks, service manuals, etc. were used to block the intake and you could see it slowly suck the center of the book in... . it did kill the engine. Madison phone book is around 5 inches I think.



Reminds me of the time I walked by the inertial filters (air intake) of an EMD locomotive under full load testing and it sucked all my paperwork against the screens.



Another interesting thing about EMDs is that if you have a propane leak in the immediate area--- you shut the units down if you can and run like hell. If the unit keeps running, the propane will collect in the airbox until gets ignited..... then its a bomb.



I never thought about the CO2 reason that MPBerk mentioned... I know that Halon can't be used... . unless you want Poision Gas in the area along with a unfazed runaway diesel.



Either way... runaways make for some good storytelling. Oo. Oo.



Jeff

 

[johnrv4]

Short story about an overspeed.

We had a Trackmobile at work that was used to move rail cars, and it had a 4-71 diesel in it. Well, they had an emergency shutoff on top of the blower that could be closed in case of a runaway engine. It looked like a steel trap door that would snuff off the air going into the blower. Well, one morning(in the winter) we got a call that it was sitting outside and wouldn't start(about 25degrees out). The usual problem was that somebody had shut the engine off incorrectly by using the emergency shutoff, which had to be manually reset. Sure enough, as we pull up, we could see white smoke coming out the exhaust pipe while the operator tried to start it. I crawled up and removed the engine cover and reset the shutoff door. My co-worker went into the cab and started the engine. It fired right up, and promptly went to an rpm that I've never heard before:--) :--) . Crap was flying off the fan blades, and my co-worker was sitting in the cab with his hands around his head waiting for parts to fly(instead of pulling the emergency shutoff ). Then the engine slowed right back down to an idle and ran fine. Come to find out, the operator had emptied a whole can of either down the air intake before we got there and didn't mention it. I couldn't smell it either, or I wouldn't have tried to start it. The engine held together, which amazed me considering the rpm and the cold temperatures out.

 

[A Johnson]

Don't know what engine a LEBHERR 900 uses, but a plugged fuel return line on a Cummins PT system will do it.

 

[Dennis Garrett]

Back in the 70's on the Santa Fe, we had a GE U-23-B locomotive do this at Wichita. I wasn't on it, but it ran beyond it's max RPM for a short time, then blew completely. It began consuming it's lube oil somehow. For a short time, it sounded like a model airplane motor, then more or less exploded & threw oil, fire & spare parts out the exhaust stack. It was a V-12 4 cycle, about 2300 HP. Max RPM should have been around 1100 or so, at full load.

 

[Champane Flight]

Detroits

The old Detroit's are famous for this. You cannot let them idle over prolonged periods of time as they will start to load up and runaway. I have even seen them run back wards!:--) I was trying to pull out a forklift from a bog one time with a KW and killed the engine (I thought) . Pushed the clutch in hastily and went to restart the engine, the starter made a weird noise and then I heard the engine still turning, but strange noise for running (came from engine being muffled by air filters. ) Saw smoke coming from air cleaners, put the transmission in ninth and dumped the clutch. That killed it! It restarted and ran fine.

 

[mikel]

We had a 6-71 in an old ford 9000 series dump truck that I made run backwards on more than one occasion. That thing was as gutless as they come, but it just kept going and going and it didn't have the power to hurt itself so it actually made a pretty good dump truck since it spent a good bit of time off-road. Anyhow, you'd be chugging along in low and hit a soft spot making the truck bog down and if you wern't fast enough it would kill the engine. On occasion it wouldn't just kill it but actually spin it backwards enough to get it to run.



It did sound a little weird with this happened and it was pretty odd to try and back up but go forwards while watching exhaust smoke come out of the air cleaner.



It was never a big deal though, just shut it off and restart it running the correct direction and all was well again.



Sorry, not exactly runaway related but someone brought up detroits running backwards.



Mike

 

[FFutch]

Screamin Detroits...

... When we would mess with the rack on one,we would usually have 3 people around when we started it. One with vise grips on the rack,one with a shut-off board at the intake,and the failsafe guy with a big hammer at the fuel lines . I seen one run-away at a diesel school and the kid threw a paper back shop manual over the blower intake,yep it ate it ,good thing it was just a trainer engine. I've seen a few 3406 cats run-off if the rack in the fuel pump wasn't right,or if someone put on a new turbo without cleaning the oil out of the after-cooler from the failed unit. A diesel runs dam good on motor oil . Hey diesels don't run-away,just the mechanics :... Doug