Detroit Diesel 3-53 would not stop after air intake closed? WTF?

If you recall, I had a Detroit Diesel 3-53 in my trailer.
After I cleaned up my yard a little bit, I dragged it out, so it sits
on a cart (properly tied down).
I tried starting it again. Just as in winter, it started VERY strong and fast. It also would not respond much to the controls.
To stop it, I covered the air intake with a wooden board.
The first time, it stopped.
Then I opened the valve cover to see if controls move anything under the valve cover. One kind of did move something.
Then I started it again a second time. (with the valve cover off a mistake).
The second time, believe it or not, it did NOT stop. It kept going, slowly, but it just would NOT stop. I pulled the fuel line, and finally, after a minute, it did stop.
My question is WTF? How exactly can it run, with the air intake closed? The board seems soft and smooth, and it is not likely (but I am open to anything) that it let any air into the engine.
Since it was outside the trailer, unlike in winter, I was not in danger of ruining my underwear, but it was freaky and unsettling to have an unstoppable diesel engine.
i
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I would guess that with the valve cover off, the engine is breathing through the "breather" hose on the valve cover? Normally the breather would be applying vacuum to the valve area & crankcase and only "breathing" the limited amount of blowby from past the rings... but with the valve cover off it's "breathing" fresh air?
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David Courtney wrote:

That sounds plausible. Also wondering why he isn't using a fuel shutoff to shutdown like every diesel I've operated uses.
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Great idea. Thanks.
I have added a fuel shutoff just 5 minutes ago. It helps in getting the situation under control.
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On Tue, 21 Jun 2011 13:04:26 -0500, Ignoramus31413

Didn't the engine have a spring loaded "damper" in the intake when you got it?
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yes, it does.
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Ignoramus3171 wrote in rec.crafts.metalworking on Wed, 22 Jun 2011 07:11:36 -0500:

FYI: A CO2 fire extinguisher can stop a runaway engine. A little pricey, but sometimes things can go real bad, real fast. If you have one, you might want to have it handy.
--

Dan H.
northshore MA.
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On Wed, 22 Jun 2011 07:11:36 -0500, Ignoramus3171

That is the normal emergency shutdown device. But as someone wrote it is a bad practice to use them as a "normal" shutdown device. If you have some strange wiring around the engine and a solenoid on the inlet damper you probably have the remnants of an automatic shut down system. They usually have sensors for high water temperature, low oil pressure and over RPM.
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wrote:

The GMC engines are two stroke and use a roots blower to provide scavenging pressure. As the blowers are lubricated by engine oil pressure if a shaft seal fails it injects lube under normal operating pressure into the incoming air stream. If you shut off the fuel under this condition the engine won't stop; if you shut off the air it will.
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On 06/21/2011 12:37 PM, Pete C. wrote:

Many Detroit Diesels from that period had an emergency shutdown that moved little arms into the path of the valve spring retainers, jamming one valve per cylinder partly open , and in so doing, killing the compression. That may be what Iggy was referring to as something moving in the valve cover area. Taking off the valve cover on those engines definitely would defeat that mechanism.
Jon
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wrote:

I believe that the spring loaded rack system was made as a substitute for the inlet damper which DD recommended be disconnected. However engines used in the oil industry are still required to have inlet air damper type shutdowns. Cheers,
John B.
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I have both the rack and air damper.
The cause of my trouble was that one injector was stuck and the rack could not pull the arms out of the injectors.
i
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On Wed, 29 Jun 2011 21:19:19 -0500, Ignoramus20088

Nope Iggie, you had an old Jimmy. You rack was the old style that could stay partially open if an injector stuck. Later versions called a single screw" will shot off all the injectors except the one that sticks Cheers,
John B.
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wrote:

A lot of errors - hmmm must be my spelling checker. It should have read "called for a "single screw" will shut off".
Cheers,
John B.
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On 06/21/2011 09:20 AM, Ignoramus31413 wrote:

Either you have a leak in your intake manifold, or leaky intake valves, or it's sucking air past the rings from the crank case. Or I have my head up my ass -- I'm no diesel mechanic, nor a truck driver.
I thought diesel engines were supposed to cut off fuel to stop, and only cut off the air as an emergency stopping measure?
I was told, a long time ago by someone who wasn't a diesel mechanic (but did drive them quite a bit, and pay for them when they broke) that a diesel can 'run away' by sucking both air and crankcase oil past the rings, and be unstoppable until it has seriously depleted the lubricating oil.
I:
1: don't know how often that happened. 2: don't know if it's true at all (but it was my dad, who didn't usually exaggerate, and who was in a position to know) 3: don't know if it's common now, as opposed to the mid 1970's when I heard it.
--

Tim Wescott
Wescott Design Services
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Tim Wescott wrote:

I owned a Volkswagan Rabbit diesel for a little while. The rings were worn and after a few weeks about an inch of crankcase oil would build up in the air box. Hitting a bump or going around a tight curve would slosh the oil into the intakes and give you a very exciting 5 seconds of about 150% full throttle. Especially if you were in that tight turn at the time.
I learned to pop the airbox open and mop out the oil about once a month.

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Maybe I have my head up my ass too.

I have added a fuel cutoff valve.

I thought that it was all about just sucking oil, not air. That is a very scary possibility.
i

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Ignoramus31413 wrote:

A chap I used to know, now dead, told me lots of interesting stories from when he worked in construction and some of those included large earth moving machinery where the diesel engines ran away. In one case the operator realised what was happening and drove the machine into the tunnel wall to stall it before any serious problems occurred. Those big machines in question had oil bath air filters IIRC and in some cases the engine would start to run on the oil in those. The chap had an interesting life, he said on another occasion he was almost killed by shrapnel from a generator donkey engine exploding when someone used compressed oxygen to start the genset rather than compressed air, that was when he was working on the Aswan dam.

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wrote:

A drilling rig? No compound?
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wrote:

Sure, see http://www.energmart.com/a,12,Drilling-rig-National-T45 -(800hp)-Drawworks,-127%E2%80%99.htm for the inventory of a small (800 HP) rig.
The compound connects the main engines to the rest of the rig, and allows the use of several engines to power the rig.
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