Runaway Engine Shutdown

[jbolt]

Since this came up as part of another thread I though it would be a good stand alone topic.



From what I gather from some previous posts it it possible to turn the full power screw in far enough once the factory stop collar has been removed to cause engine runaway.



What are the best methods for rapid shutdown?



1. Key off?

2. Shut down lever on pump?

3. Pull wire to fuel soleniod?

4. ?



Second part of this is:



What is the best way to creep up on the fueling (fuel power screw) without getting a runaway?



One of nascarmarks comments was:



"Generaly you're safe when you rev the engine and it has no hesatation coming down to idle. "



Any other tasty tid bits (words from the wise) on this?



Jay

 

[formula]

Jay,

The runaway condition you're about to experiment with is caused when you turn the full load screw way in, it adjusts the internal linkages so far that the governor cannot counteract the control collar travel.



The fastest and most effective way to kill the engine would be to choke off its air supply either by covering the turbo intake or disconnecting the intake tube at the intake horn. ( do not use your hand :-laf )I used the latter method and had Dad sit in the cab and watch the tach. If it ran away, I could quickly cover the intake horn with a piece of lexan that I had handy.



The only way to eliminate this condidion is to back off the full load screw.



Shutting off the key and disconnecting the wire from the shutoff solenoid do the same thing, but due to the pressures inside the pump, may not work in this situation. The shutoff lever also may not work.

BE PREPARED!



As you turn the full load screw in, you'll notice that it turns pretty easily to a point then becomes much harder to turn. It is at this point that the strange and unusual things will begin to happen. The first thing is that the engine's midrange speed will become flaky, it will want to rev from low to high rpm with little movement of the throttle lever in the middle of its throw, but the governor will still work to control the top end. If you turn more, the governor will cease to function altogether and you will get full rpms with only a little bit of throttle lever travel. If you keep turning more then you will get runaway and the engine will not come back down to idle or can just take off on you. There is only about 1/2 turn or so between the point where the governor starts acting funny and runaway.



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Sean

 

[Philip]

Like formula said. Have your intake hose off. Have something heavy and solid to block it with. Do not trust in any of the built in features of the pump. On a runway with the adjustments you are doing. . If it can pull engine oil from anywhere. It will run untill the pan runs dry.

 

[RGT]

I wonder if an exhaust brake would shut things down enough that you could get out and cover the air intake before doing damage? I used to work on a couple of Detroit 71 series gensets and they all had shut down system that comprised a solenoid tripped shutter that chocked the engine, maybe you guys on the outer limits need to consider this, or I suppose you could have a co2 extinguisher plumbed into the air intake to be used in an emergency.....

 

[jbolt]

Originally posted by Philip

If it can pull engine oil from anywhere. It will run untill the pan runs dry.

Not sure I follow you on this statement



Jay

 

[Midnite]

Jay, your engine will happily run on engine oil, and if there is a leak (usually at the turbo from what I've read), then the oil will enter the engine through the intake, and can cause a runaway by itself. In this case, the rate of the leak would actually be your throttle, and nothing you do to the injection pump would kill the engine--the only way to stop it is to deprive it of air, either by something over the turbo inlet, or by shooting an inert gas (CO2 or something else) into the intake.



Thankfully I've never actually experienced this, but if anyone else here has and sees that I've missed anything, hopefully they'll pitch in.



Mike

 

[formula]

Originally posted by jbolt

Not sure I follow you on this statement



Jay

Jay,

This probably won't happen in your case, but it's something to be aware of. The diesel engine will run on darn near any kind of fuel that's fed to it. So, if you blow a turbo gasket badly, it'll run on the engine oil. If it blows rings or various other internal parts then it can suck oil and run. If it sucks up flammable vapors (propane, methane, gasoline, etc. ) into the intake, it can run. The only way to shut it off in these cases it to choke off its air supply.



I remember a time when I saw a D8 run over a propane tank..... it sucked in the cloud of propane into the engine and the engine took of like mad



Sean

 

[Philip]

That was a good explanation Midnite.



Yes I have seen a few run aways over the years of my working in the field. It is not pretty if you can't get the air shut off to the engine.



On Detroit's the first thing I recommend to the owner is to buy the air shutoff kits for the engine they running. All it consists of is a flap that is cable or solenoid operated. It mounts right at the air inlet to the supercharger. If you get a run away you trip it and it pops closed and kills the engine. You have to manual reset it also. No auto reset.

 

[jbolt]

:--)

 

[nascar mark]

What are the best methods for rapid shutdown?



1. Key off?

2. Shut down lever on pump?

3. Pull wire to fuel soleniod?

4. ?



None of these will shut down a runaway. Even a fire extinguisher is iffy unless done right, as if you run out before turbo spools down, it may spark back up and runaway again.

I had a guy phone me yesterday that sprayed carb cleaner into the intake of his turbo to clean up the compressor wheel. Well a complete engine rebuild later he still is needs help repairing his pump, because lack of knowledge. This is why I stressed/warned our group to be prepared... ...



A piece of plywood will work nicely or back the power screw out to relieve the pressure. I tack a nut on all my pumps that I play with.

 

[JFitzgerald]

Originally posted by formula

As you turn the full load screw in, you'll notice that it turns pretty easily to a point then becomes much harder to turn.

To go along with Mark's comment in Jay's original post -



Is it safe to say that the full load screw could be turned in up to the point it becomes harder to turn, without the engine running away? And how risky is this in regards to pump life?

 

[formula]

Originally posted by JFitzgerald

To go along with Mark's comment in Jay's original post -



Is it safe to say that the full load screw could be turned in up to the point it becomes harder to turn, without the engine running away? And how risky is this in regards to pump life?

Well, probably, but you should still be prepared to kill the engine if you're going to play around in this area.



As far as pump life, turning in the full load screw increases the maximum effective operating stroke of the pump's plunger. Longer stroke = more load on the internals of the pump (cam plate and rollers, etc) Maybe it will last a long time, maybe not, there are no guarantees.



Sean

 

[Old Smoky]

Hey Sean,

Are you sure the length of the plunger stroke changes? Or, could it just be that the control sleeve is moved farther to allow for increased fuel delivery? I have also heard that the tension on several springs is increased when the "power screw" is turned in.



Mike

 

[formula]

Mike,



I wrote "maximum effective operating stroke"

The total stroke length of the plunger is always the same and is dictated by the cam plate profile



Sean

 

[Old Smoky]

Sean,

I thought the length of the stroke was always the same on the VE44. Just wanted to be sure since you wrote “longer stroke = more load on …” It’s been a while since I have been through fuel systems, and there are so many pumps out there. I guess I will have to break out the books and refresh my memory.



There has been a lot of good information in this forum lately. Its good to see it so active. Keep it up guys!



Mike

 

[JFitzgerald]

Originally posted by formula

Well, probably, but you should still be prepared to kill the engine if you're going to play around in this area.



As far as pump life, turning in the full load screw increases the maximum effective operating stroke of the pump's plunger. Longer stroke = more load on the internals of the pump (cam plate and rollers, etc) Maybe it will last a long time, maybe not, there are no guarantees.



Sean

Thanks for the reply. That's what I was looking for - what technically is behind the idea that turning this screw effects pump life. I want to understand the cause, so I can make a more educated decision whether to "push the limit" a bit more. OK, we're increasing the effective stroke. Is this also increasing internal pump pressures, or just flow?



I'll definitely be ready to block the air off if I go there - I'd rather not experiment with how long my Cummins can live at runaway speed!



Mike is right. It's good to see this stuff being discussed.

 

[Midnite]

Originally posted by Old Smoky

Sean,

I thought the length of the stroke was always the same on the VE44.

Just to clarify, there actually isn't any such thing as a VE44. When people refer to our pumps as a "VE pump", they're using the full name, not an abbreviation.



No big deal, but it's always good to avoid confusion...



Mike

 

[Old Smoky]

I believe I had read somewhere on this site where our fuel injection pump was referred to as a "VE44. " Hmmmm... .



Mike