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B75 711 turbo ran away


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Just started up the mack to take a nice Sunday drive with my 3 year old daughter to get ice cream and it ran away. Ran beautiful when I parked it in the barn last year.  Oh man did I go into scramble mode. Got intake pipe off and stuffed my t shirt in there. Danm thing wouldn't stall. Just set down to a low idle. Had to find plastic to wrap over the t shirt to get it to stall. Got it idled down quick enough but took good time too get the dam thing to stall out. Any ideas? Fuel is probably 2 if not 3 years old, Startin to smell like kerosene. Injection pump problem? Or running off oil that leaked down? Never had issues before.  It's a 711 turbo in a b75 with triplex. Old pics but pics are always good to look at

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2 hours ago, mrgumby said:

Stuck rack maybe?   Is turbo sucking oil?

Nice looking B-75 in any case!  Only experience I ever had was I had rented a good size Deutz powered boom lift to stain my house.  I'm up in the air and all of a sudden rpms change and it starts smoking like crazy. I get down real quick and it wont shut off.  I pulled the air intake hose off the air cleaner and jammed a rag in it.  Rental outfit told me it had a cracked ring and was pulling oil.

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You can look inside the tubes and the turbo and see if it's gooey. To make it run away it would be REALLY messy in there and low oil level. It's not much work to verify. If you don't see a big oily mess you have a problem in the pump.  I'm just glad the old girl didn't end up mortally wounded. These things are tough and you cut the air supply quick. 

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20 hours ago, Freightrain said:

A handful of bolts will get the cover off and you can see if the plungers are stuck.

Last I went by this logic I had a fuel elbow broken which didn't allow me to place a wrench on one of the bolts. It didn't spin over its threads as I supposed to

Никогда не бывает слишком много грузовиков! leversole 11.2012

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On 9/2/2020 at 1:41 AM, tippi98custom said:

Yes after thinking about it that night it must be the injection pump it stuck at full throttle internally because it was not smoking when it was revved out, once I cut the air off obviously it started chugging smoke so I don't think it was running on oil

Agree. A long while back I had 1975 Mercedes car with diesel engine. One day I started it and noted more smoke off the exhaust pipe than I used to see and when I pressed the pump knob in (the same rack control setup as an old truck) it didn't stall. I removed the air filter hose and closed the hole by a palm of my hand (Later I figured it was not a good idea but the hole wasn't big so no damage to the hand). Got the engine stopped. Started once more and stopped the same way again. But there was really heavy and smelly grey smoke and I saw no oil level on the stick after half an hour I stopped that thing. Later I discowered the issue was a vacuum pump which supposed to sypply brakes. It should take air from vacuum buster line and put it into intake manifold. The pump had diaphragm. It collapsed so the pump started putting not only excessive air into the intake but also the engine oil.

Никогда не бывает слишком много грузовиков! leversole 11.2012

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  • 4 weeks later...
On 9/25/2020 at 9:31 PM, Milaca said:

Thirty years ago I had a GM diesel run-away in an Allis-Chalmers HD9 dozer. I suffocated the intake with a steel coffee can until the engine shut down. The mechanic diagnosed it as a stuck governor. He repaired the governor then all was fine.

I've seen a lot of the 2 cycle DDs with emergency shutoffs...flapper door on the air intake. Handy thing to have!

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7 hours ago, h67st said:

I've seen a lot of the 2 cycle DDs with emergency shutoffs...flapper door on the air intake. Handy thing to have!

I have never seen a screamer with out the flap 

Wonder if we only got screamers with the flaps in Australia, I wouldn't think so as they are sort of well known for their ability to run away 

 

Paul

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  • 2 weeks later...
  • 3 months later...

I have had 2 macks "run away".

First wa a 74-75 RD600 with 237 engine. The injector pump keyed sheared as it was reved up and would not come off the 2300 rpm the governor was set at.  I got the load of asphalt off, then stalled it by putting in 5th and letting out the clutch.

Second was a 2 valve 350 that came out of a salvage yard and was swapped into a first generation superliner after the V8 gave up the ghost. Something in the injector pump let go, and it took off as I was crossing a highway.

I got about 1/4 mile away from the highway next to an open field and started braking.  Got it down from pegged 3200rpm tach to around 200 rpm when the clutch let go.

I could not open the hood to cover the air filter, so I stood behind the trailer to not get hit with parts when it blew.

The belts flew off a few minutes later and it started getting hot. It ran pegged 3200 rpm tach for over 5 minutes before it heat seized.

While it was screaming there were flames 3 foot out of the stacks. No one wanted to get near it, so the cops just blocked the road, and the fire dept stood by with a pumper and 6000 gallon tanker incase it caused a fire.

When we finally got it home, it was trash. The crank was blue from the heat.

 

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when you are up to your armpits in alligators,

it is hard to remember you only came in to drain the swamp..

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