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Author Topic: Runaway Detroit 6-71 - Last night's excitement  (Read 8450 times)
WEC4104
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« on: July 22, 2006, 12:42:15 PM »

It was Friday evening, and I've got the wife & kids packed up for a weekend away camping. I have only put 1100 miles on a fresh inframe of my 4104's 6-71, and she is absolutely purring. I am cruising westboard on the PA turnpike wearing a big S.E.G.

Everything was going well for the first 30 miles. Then, as I am cruising down a slight grade, I feel I am going pretty fast. I sneak a quick glance at the gauges and see I am doing 70 mph at about 2450 rpms!† I am governed at about 64 / 2200, so I backed completely off the accelerator and still have to brake a bit to lower the rpms. It was a slight downhill grade but certainly not THAT steep.

As I continued on, I discovered that I could run at about 62 mph without even touching the accelerator. Uh-oh.† I jabbed at the pedal a few times wondering if I had a throttle cable hung up.† No difference.† I tried pushing in the clutch briefly, and the rpms immediately shot up.† More uh-oh.

So there I am cruising down the PA turnpike, in thankfully light traffic, pondering my options.† I know from replacing a dashboard light bulb recently that a previous owner had disconnected the EMERG. SHUTDOWN switch on the dash.† †Of course, I could just keep driving until I run out of fuel, but remembering that I had just topped of my tanks, I quickly realize that would be somewhere out past Chicago.

I also realize that if I take her out of gear, I stand little chance of ever getting her back in any gear. Likewise, stopping the bus by depressing the clutch is going to take the rpms into the stratosphere, turning my freshly rebuilt 6-71 into scrap metal.† As a test, I depress the clutch again for just an instant. The rate at which the rpms rise makes me quickly rule out the possibility of parking and rushing to the back to block the air intake.

As I continue to cruise west, I keep having flashbacks of the Sandra Bullock movie Speed.

So in a bus traveling at highway speed, which will win out?:† the 6-71 in runaway operation, or the 4104's brakes?† I am not sure I want to discover the answer at some turnpike toll booth.

Up ahead I see signs for a rest area. The off ramp looks flat with a gradual curve, and there are big parking lots for trucks in the back. Quickly, I decide this looks like my best option. I start bleeding off speed using the brakes. I get off at the ramp doing 35 mph, and by the time I am moving through the back parking lot, I am down to 20 (still in 4th gear). I pull into a parking slot and hit the brakes to execute an intentional stall and kill the engine.† †Whew! I'm shut down.† Not the nicest thing to do to the engine, but given my options it was the best I could come up with.

I caught my breath, relaxed my "pucker factor", and went back to look in the engine compartment.† There was quite a bit of oil dripping, especially on the radiator side. Some of the wet areas were up pretty high too, although it might have been thrown up there by the fan blades.† I couldn't see any apparent throttle or govenor problems.† The oil level was down quite a bit, but still in the acceptable range on the dipstick.

I am not very knowledgeable about runaway diesels, but I think I have heard that they can happen from the engine running on it's motor oil.† †I'll mention that the N60 injectors were all replaced with the engine rebuild.

Fortunately, our family was planning to go to two different places on Saturday, and for the first time in six years, my wife was following in her car. The 4104 has never broken down on us before, and we have never had a car with us before.† :}

So there she sits, in the parking lot of the Rest Area as I await contact with my mechanic. I am hoping I can find a solution that won't require towing. Suggestions from Board members are always welcome, too.† (Aside from "Get the Engine Shutdown switch connected", which is a given.
« Last Edit: July 23, 2006, 10:10:44 AM by WEC4104 » Logged

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Mike in GA
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« Reply #1 on: July 22, 2006, 02:53:48 PM »

Wow! Fascinating situation. Every busnut's nightmare.  Please do tell us how this all works out, since maybe we can learn how to avoid this, etc.  Besy of luck!
Mike in GA
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DuaneMC7
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« Reply #2 on: July 22, 2006, 03:00:10 PM »

Wow! Quite a story!  Sorry I have no help to offer, but this is a reminder to us all to have our emergency shut downs in working order.  Good luck and let us know how it works out.

Duane.
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FloridaCliff
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« Reply #3 on: July 22, 2006, 03:16:21 PM »

Wow, What a story.

And i thought my exhaust leak and fire was scary Shocked

By the way, great job on keeping your head and doing the right thing.

Having loved ones with you only intensifies the experience,

Please let us know what you find.

Cliff
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WEC4104
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« Reply #4 on: July 22, 2006, 03:58:17 PM »

Ironically, I already had plans to get the EMERG STOP switch operational again, and had begun to start on it.

For several years, I did not realize my switch was non-operational. I was always concerned about the switch location and the fact that it blends in against a bunch of similar toggles. My concern was that it is too easy to hit by mistake. What if I got into a tight city location and, in the middle of a turn, needed to back up a few feet and then pull forward again? It would not be hard to reach for the REVERSE switch and hit the EMERG STOP by mistake. Then I would have to stop in traffic and go back to the engine compartment, reset it and restart, and everything. Of course, it would be raining and at night when I had to do this.†

In browsing the auto parts stores lately, I noticed that toggle switches with flip covers have become popular with the boy-racer crowd.† They take a standard toggle switch and add a hinged cover, like it was a missle launch switch or something. Guess they use them for Nitrous Oxide, or something. I bought one a few weeks ago for my EMERG STOP switch. The color of the cover was bright red, and a little too much for my tastes, but I was able to repaint it the same color as my dash.† I installed it this week, and it blends in nicely with the dash. In the process of installing it I found out that the old switch had not been operational. I think a previous owner had done more than disconnect the dash switch, and I have not had a chance of checking the rest of the circuit to get the newly installed switch working. In any event, I think this will eliminate my fear of accidentally tripping the shutdown.†

Those of you with the dash toggle shutdown switch, I offer that as an easy enhancement.

... Busless for 24 hours and counting.† I'll keep you posted.
« Last Edit: July 23, 2006, 10:16:02 AM by WEC4104 » Logged

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DrivingMissLazy
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« Reply #5 on: July 22, 2006, 04:29:58 PM »

I had the same thing happen on my 4104. I topped a mountain and when I started down the other side, she just kept on going. Fortunately I had my emergency shutdown switch working and got her stopped by the side of the road.

It has been so long that I can not remember how I determined it, but I discovered that my rack was stuck open. I removed the valve cover and found one injector stuck open which was holding the rack open. I just loosened the one injector and the rack immediately returned to the closed position.

I replaced the valve cover and drove her home on five instead six. The only mistake I made was I did not get the valve cover gasket on properly and I had a LOT of oil everywhere when I got home.
Richard
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« Reply #6 on: July 22, 2006, 07:40:18 PM »

Hey WEC, way to keep your cool man, nice job.

My 4104 has a couple of those safety toggles with the flip covers too - the guy that did the conversion put them on the switches that you really REALLY don't want to hit accidentally. (Starter, Reverse, Estop).  They're red for a reason, but I can see your point too.  They're nice, I like 'em.

Let us know how it goes.  I've heard that a slobber tube not draining properly can allow bad stuff to accumulate in a bad spot and that the engine can run away that way.  Something to check? (just repeating hearsay - some real expert chime in here please).

Good luck pal,

Casper
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« Reply #7 on: July 22, 2006, 09:30:22 PM »

when i drove a truck i bogged the motor and it ran backwards,but it did not runaway
i will check the shutdown on my 4104.thats a scary deal
good luck
      Bernie
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roadrunnertex
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« Reply #8 on: July 23, 2006, 06:43:12 AM »

Run away Detroit.
Sounds like it was a exciting time for you.
One of the ways to stop the runaway on any detroit take a wrench and loosen the main fuel supply line.
Another is use a CO/2 fire extingusher spray the CO/2 into the engine air inlet.Please( DO NOT) use a dry powder fire extingusher.
This might be a good time for us folks to check out our emergency shut down system on our coaches.
Folks make sure you do this with the engine not running.
And also make sure that you reset the flaper valve when you finsh your check.
Just a thought on my part.
jlv
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TomC
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« Reply #9 on: July 23, 2006, 06:55:59 AM »

A couple of things on runnaways (engines that is).  The newer versions of Detroit injectors-any with a letter in them- have been redesigned so to have spring back to them, so no flapper is necessary.  You won't find emergency flappers on turbo engines.  Also, do not feed the breather tube back into the intake.  With oil mist or a failure the engine will run on oil.  The new '07 engines are going to have closed breather systems where the old road tube is going to dump into an oil separator (another part that will have to be serviced) then into the intake air.  No matter what engine you have, if you have an engine failure- turbo oil seal leak, blower seal leaking, broken or worn rings, etc, any engine runs the risk of running on.  If you have a non turbo'ed engine with a three digit numbered injector, I would keep the emergency shut down in working order.  Like all systems on the bus, they should be in good running condition.  Good Luck, TomC
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« Reply #10 on: July 23, 2006, 09:55:56 AM »

TomC
  How would you stop a runnaway turbo if, lord for bid, it happend. Just want to know because a fuel suttoff switch dose'nt
sound like it would work

Ray with the littlehouse ['77MC8]
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Barn Owl
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« Reply #11 on: July 23, 2006, 10:39:15 AM »

What would one do if you had an auto and your emergency cutoff was inop in this situation?
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WEC4104
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« Reply #12 on: July 23, 2006, 11:21:06 AM »

Barn:

Took me a minute to figure out you were asking about "auto" as in automatic transmission, (not car). I'm a little slow today.

With an automatic transmission, the question hinges on whether the brakes would be strong enough to hold back the coach as it keeps downshifting. I'm betting there would be no choice other than take it out of gear to get it stopped.

So the best scenario would be if I could get the bus stopped safely in a remote location, get my family quickly off, and run like h***.    From my brief experience, the RPMs rise very quickly with no engine load (just blip your throttle pedal while parked sometime and you'll get the idea).

There are those folks that might recommend breaking out a wrench for disconnecting the fuel line.  They've got bigger stones than mine. I know what my 6-71 sounds like running at it's normal governed max speed.  Tack on an extra 1000 rpm and there is no way I'm going to be standing next to it diddling with a wrench in my hand. Taking the bath mat out of the tub and holding it against the air intake might work. Squirt a fire extinguisher at the intake?  Maybe. (Although mine are dry chemical, not CO2)  So that would come down to a question of "Make a mess out of the engine while risking my own safety" versus "Let the engine destroy itself on it's own"  I honestly don't know which I would choose in the heat of the moment.

Of course, if I had an automatic, it wouldn't take me as long to use up all the fuel in the tank either :}
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DrivingMissLazy
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« Reply #13 on: July 23, 2006, 12:15:04 PM »

But did he have a runaway engine or just a stuck qccellerator or rack? I do not think he ever took it out of gear long enough to find out. Yes theos babies will sound like a runaway if they go up to the governor but it will really not hurt them.
Richard
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« Reply #14 on: July 23, 2006, 12:16:22 PM »

Looks like you have an injector stuck, like Tomc said.       If you are tryin to do something with it,---- pop the valve cover off, and check the rack. See if it is stuck, or someone has put the cotterpin in the wrong way, and it is sticking in the open position.     Try to move the rack, not forcing it to open and close.   If it is stuck, than you will have to find which injector is stuck, and just take the screws out, and move the little actuator to the side, leaving the screws out.  Make sure there is nothing else restricting the movement of the rack, and put the valve cover back on,  makeing sure it is seated down, and tighten it up.
      Now--  BEFORE YOU START THE ENGINE, PUT THE TRANSMISSION IN 4th GEAR, than statr the engine.   Just in case there is still simething causing the engine to overspeed.

Keep us posted, and I hope this will help a little.
Steve
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