Runaway diesel engines

[carmarche]

Originally Posted by deblen

Every diesel should come equipped IMHO
https://www.amot.com/en/products/die...ring-database/

Thx for the link ! Was thinking this was the obvious solution ! Wouldn’t think there would be so many choices/styles. (Only intake size differences) Hopefully one is made for Yanmar or be able to cross-fit.

[sinnerman]

Originally Posted by deblen

Every diesel should come equipped IMHO
https://www.amot.com/en/products/die...ring-database/

They have these installed on diesels on offshore drilling rigs. They are called "rig savers"...

[sailorladd]

I built a sailboat in South Africa in the mid to late seventees, and I happened to be single handing a few years later in the False Bay area in Simonstown, where I lived.
It was a Tuesday morning and I had brisk south easterly trades. Unbeknownst to me, Tuesday's was the official navy training day in the bay and it was forbidden to go out sailing in this area for some hours (I forget what the hours were). I was somewhat of a novice and was practicing solo sailing... and was on my last tack back towards the mooring area, and had my little diesel engine running (Yanmar SM 10, I believe it was called, a one cylinder ten h.p. cast iron body)
I was heeled over to port as my boat was very tender back then, and all of a sudden two things happen that put me in an instant panic!
I had seen a navy frigate maneuvering about a mile or two off my starboard bow, and was taking precautions to keep as far away as possible.

Suddenly my engine started picking up revolutions and rapidly it reached a terrifying rpm...I had just recently heard about diesels that could "run away" and I flew down below, abandoning my tiller and ripping away the engine cover ...I was in absolute panic mode I did not know what to do, but in the back of my mind I recall that one way to stop this was to starve it of air, and to stuff a rag into the air intake. I had no rags handy, and I looked about wildly for something to use, I happened to glance out the stern of the boat and to my horror saw how close this navy frigate had suddenly become!

The engine was still screaming at the highest possible rpm's and I grabbed a pillow from my buck which was right next to the engine, and started stuffing it into the air intake ...The pillow was sucked partially into this and slowly the revolutions started coming down until I was able to pull the stop cable and kill it.
What had apparently happened, according to the mechanic who had just worked on my engine a week or two before, was that he had had to remove a sump oil strike pan (this had a breather pipe attached to it, and he confessed that he may have replaced it upside down. What must have triggered off this terrifying incident was that as my boat heeled over to port, the sump oil was now being sucked into the head, via this breather pipe, now upside down and full of oil...and it started running on this sump oil, with obviously no governor control!

The plate was soon turned back around by the mechanic and I NEVER, thank God, had that problem again!

The engine was a Yanmar YSM 12, now that I think about it....and I don't mind saying that that little one lunger served my 7 ton 31 foot sailboat for over twenty five years of excellent, faithful service and I would highly recommend it to anyone! It finally wore it's heart out and I installed a 24 hp Vetus... but wish I had replaced it with another Yanmar!

There are several memorable (engine) incidents mentioned in a sailing book I wrote after my journey (Days of Deja vu) you may find useful...

[Shaneesprit]

There is a huge difference between a runaway stuck rack, which mostly just going to scream at you at full revs without damaging anything, diesels are designed to run on full power forever. Well almost.
Where as a diesel running away on its own oil has zero control and is more likely to fail and projectile it’s internal parts externally through the side of the block. Even found them imbedded in the engine along side which was probably 6 feet away.
The later is most often caused by lack of maintenance, or improper use.
Such as not replacing the fuel lift pump at X years just to ensure it doesn’t leak, or running the engine to charge batteries for long periods, then only being gentle with the throttle while motoring.
I was in a car once where the engine tried to runaway - simple case of pressing the brakes did just fine, cause was extreme mileage and a driver who was very very light on the throttle.

[col50]

Originally Posted by Jim Cate

I find the above to hard to believe. Having spent much of my early life desperately trying to get more HP out of engines, realizing a X10 increment seems wildly improbable. The limiting factors would be the max airflow that can be obtained through the intake passages and valve float at high RPMs.

Runaway engines are a scary phenomenon for sure but hyperbole ain't justified whilst discussing them.

Jim

Exactly. How do these myths get started?

[Briis]

Originally Posted by Pete7

I am concerned about this advice and hope no one will try an put a hand anywhere near the air intake of a run away diesel. There is the potential for very serious injury.

Mine is a 2.7 liter naturally aspirated engine and has around 1.5" pipe intake from the manifold side once the airbox is removed (I've intentionally made it easy, takes me me just few seconds to remove it). I've tried to kill it at near max RPMs and there nowhere near enough vacuum power to do the damage with my bare hand covering it. High RPM turbos and higher revving engines may be different matter and I agree it shouldn't be a recommended practice. I've said before, a prepared rag or a very thick plastic bag (over airbox if it doesn't come off fast) might be preferred solution in terms of safety.

Originally Posted by col50

Exactly. How do these myths get started?

You ought to dyno one then to prove your point then, I reckon.

"Diesel engine runaway is an occurrence in diesel engines, in which the engine draws extra fuel from an unintended source and overspeeds at higher and higher RPM, producing up to ten times the engine's rated output until destroyed by mechanical failure or bearing seizure due to a lack of lubrication.[1] Hot-bulb engines and jet engines can also run away via the same process." Wikipedia.

Provided if the engine oil found it's way into combustion chamber and into all cylinders then from what I understand the only limit of the RPMs in a runaway is basically air intake amount (for combustion efficiency, and a crazy WHOLE lot more with a turbo engine!) and inertial weight of mechanical parts with their respective friction (pistons/rings, conrods, crankshaft). Hence all the engines act different in a runaway - depending how high they over-rev up on those factors. The ones with huge air intake manifold and short-stroke definitely can make up multiple times of stated max HP (which comes from from RPMs anyway) power due to multiple times over-revving from those factors. Yet a non-turbo heavy long-stroke engines with a very small air intakes may not over-rev up as much in a runaway. Go figure, since it's only a theory...

[hpaabor]

When I changed the engine mounts of the Yanmar 30 I apparently damaged the governor when setting the motor back. The result was the sound of a diving airplane. Mechanic said runaway usually describes people when they are around such a motor. I did eventually think to cut off the fuel supply which did work. I was surprised to still have a working motor.

[Brendo77]

Yanmar 2GM... probably less than an hour run time after a rebuild...
Engine revved pretty hard but the fuel shutoff didn't work.
I ran down and flipped the decompression levers on top of the engine and it stopped. Luckily I was at the dock so no dramas.
I was not happy.
I asked an injector pump company what could have caused that and they said they hadn't seen anything like that before on Yanmar pumps...

I still don't like thinking about it but I now have two shiny new 3YM's...

[skipperpete]

Well, that’s a new way for a GM cartridge pump to cause a runaway, I guess the locating screw for the cam follower came loose but to break the side out of the pump body is next level destruction.... I guess the camshaft was badly damaged too.
The runaway engine enigma is fertile ground for the propagators of urban myths.... among them is the ever increasing potential manifold vacuum, another is the fabulous increase in power output, Diesel engine have a heavy rotating mass and break fairly quickly if they overspeed .... dragcar and race car drivers are very familiar with high rpm failures and go to extreme lengths to lighten up and strengthen that mass with lighter steel flywheels, not heavy cast iron; ultra sophisticated lightweight pistons and con-rods etc, but even with the best formula one technology, engines often fly apart.
There are distinct types of overspeed , the most common is “high idle” where the engine is operated with no load and the controller at maximum fuel... the engine is still under the control of the limiting speed governor but goes a few hundred rpm higher than the published max rpm.... perfectly normal. It’s still controlled.
Far less normal is when an injector plunger hangs up in a Bosch type (rotating plunger with helix) injector pump. The plungers are all linked and rotate as one until there’s a seizure then they all are locked at the same delivery and I promise you that the amount of fuel to cause a destructive overspeed unloaded is surprisingly small, not much above idle will do it and if the seizure of the plunger occurs under load and the load is removed (ie neutral is selected) the sky’s the limit but usually mechanical failure ends the drama, thrown or dropped conrods, dropped valves are the most common events but once , back in the days of 1200- 2100 rpm engines there was a threat of the usually very heavy flywheel reaching its tensile limit and flying apart, cast iron gives up easily. This is another smoko table yarn diesel mechanics tell, we’ve all talked about it over a coffee......but never seen it happen even though it’s totally possible.

[DShant]

I had a 2006 27 foot cabin cruiser with a single Volvo like 300 or 350HP. That boat had about 400 hours on it in 2011 or so when coming back to the harbor after an uneventful trip the engine all of a sudden went crazy.
It started over revving and smoking great clouds of white smoke. The captain threw it in neutral and tried to get to the air intake but it was on the other side of the engine and with the engine howling away at greater and greater speeds and giving off reams of smoke no one in their right mind wanted to lean over it to get at that intake.
The Captain finally pulled off the fuel filter which was accessible and that slowed it a bit but then it caught on fire and kept on revving. We fired extinguishers at it but in the end it just blew up. Parts flew and destroyed the engine compartment. The fire guys showed up fairly quickly and put out the fire.

As to the myths. That thing was roaring like a beast and smoking like a volcano. I would believe anything anyone said about increased HP. As to why it happened, we had an insurance adjuster who couldn't figure it out and hired an engine specialist who finally said that either an injector had blown a tip? or the turbo had started sucking in engine oil or whatever. They never did tell us straight what the issue was.
Believe it or not the insurance company totaled the boat and paid off the full amount of our policy. The only claim I've ever had on a boat.

[Tillikum]

A risk with worn cylinder bores, or just stuck piston rings causing the lubricating oil to be pulled past the rings into the combustion chambers. The faster she goes the greater the suction pulling in the oil until no more oil can be pulled in or the engine seizes or the rods/crank/pistons fail. Happened to me the odd time when taking a certain truck up a certain hill. Fortunately the fuel shut off was enough to kill it, but I later took off the air intake tube that went from the grill to the air filter and kept a piece of plywood tucked in under the hood to hold over the intake in case the fuel shut off was not enough to stop it. Diesel engines like a nice hard workout now and then if not run hard all the time, and in fact that old truck always ran better after a nice little runaway!

[Sailshabby]

Grossly overfilled my Westerbeke with oil (don’t ask). Thankfully it ran fine while negotiating some tight channels leaving the dock and then took off like a racehorse. Wouldn’t obey throttle commands and Turing it off with the key didn’t help. Finally shutdown with a pound bang, lots of smoke, and we breathed a little sigh of relief. Didn’t restart it out of caution, got towed in, problem diagnosed and remediated, and with fingers crossed, fired it up successfully. No lasting effects a hundred hours later. Lucky favors drunks and sailors, twice over when one combines both!

[captchetco]

Personal experience: Just installed newly professionally rebuilt Perkins 4-108. First start. Engine fired up, and just kept accelerating. My helper grabbed a can of green beans and stuck it over air intake, killing engine. The can of beans was badly distorted, convincing me my arm would have been sucked in up to elbow, if I had put may hand over the intake.
I now keep a 6" piece of 2x6 tucked adjacent to motor, as an emergency "killer", but in 18 years more, it has never reoccured. Problem was in fuel linkage.

[CrispyCringle]

I cant see how, unless the intake diameter is pretty big (2"+) that your going to get your hand sucked into the intake on a runaway. You cant get less pressure than zero and most intakes on a typical sailboat are probably 1.5" or so in diameter. With a small hole its just not going to be that much suction. Now, would I want to stick my hand over the intake if my engine was roaring away and pouring out smoke? Probably not. But sitting in the comfort of my sofa, I cant see it as a huge real danger.

[Djarraluda]

Originally Posted by Diamond-Esp

SkipperPete, Yes I had an incident several years ago whilst sailing from Tasmania to WA (Australia). It happened at about 2am (of course), we tried to get to the air intake but it was at the rear of the engine with a pipe pointing downward. There was no chance of getting access from the front engine hatch without lying on the screaming engine. We tried to access from the rear, but the yacht had completed the Sydney - Hobart race and the lockers providing access were filled with race sails. One of us shut off the diesel in case of injecting diesel into the hot space (so hot that I was worried the fuel lines might melt). Anyway, the engine let out one final squeak before we had silence... It only lasted several minutes (a long time), and the heat was unbelievable, we consoled ourselves by sitting in the cockpit eating a whole packet of Tim Tam's... Not a fun experience... I could provide a lot more detail about what we had done previously, and what I should have done to prevent the problem but in hindsight everything is easy!!

Now Now, how can "eating a whole packet of Tim Tams..." be considered as "Not a fun experience"? Seriously though, yes I had the issue when the foolish mechanic who had just done an oil change, yes Moi, had overfilled the sump and thought it would not matter! It was a YSE8 in excellent condition so not a case of worn rings or valve stems etc, just a moment of silliness on my part. Blocked air intake and peace was restored, engine ran beaut for years afterwards, luckily but at the time I was petrified of loosing the con rod through the sump and then through the hull!