Runaway Diesel???

[illflem]

mikel, Deutz makes one and two cylinder diesels used in fishing boats that are designed to run forwards and backwards. Eliminates a gearbox if you want to go in reverse. A lever switches the valves though so the exhaust doesn't come out the air cleaner.

 

[Camara]

Hey Bigdig, in the early 80's a friend of my fathers was building a 65' fishing trawler in Weymouth. They put in a 12v71n Detroit. There it was down in the engine room all nice pretty & brand spanking new. Hooked it up, and started it up to break it in a little. It started at full throttle and kept going. We stuffed a jacket in the intake of the blower. All we got was sparks out the exhaust. We left. About 45 minutes later it stopped. Pieces everywhere. The engine room completely wiped out. Large pieces landed in the water. We never did recover all of it. GM gave hm his money back! That boat is now in Florida with 2 NTC 350 Cummins engines in it and to this day they have not even been opened up to adjust the valves. The boat owner religiously changes the oil and all the filters every 200 hours. Does not believe in testing the oil for contaminants. Says it's a waste of money.



As for the leibher... ... ... Thats the problem. Wouldn't give you a nickle for it as scrap metal. Don't like them, never did, never will. My own personal opinion

 

[BIGDIG]

Originally posted by Camara





As for the leibher... ... ... Thats the problem. Wouldn't give you a nickle for it as scrap metal. Don't like them, never did, never will. My own personal opinion

You should see it now,covered in shotcrete,pieces broken off lites covered up with muck,It's too bad it didn't blow-up. We would have had some down time... . sitting around making more money to pay for my truck. .

 

[RThompson]

Runaway Detroits are no fun shutting down. I had one get away while running the the rack. It started picking up RPMs so I went to the blower for the air shutdown valve. Found out there wasn't one. It was a 4-53 in a Drott shovel. By this time it was well past any governed speed and was spewing smoke and crankcase oil straight up in the air. Crawling back up the motor house to cram coveralls into the air cleaner inlet was an adventure I don't care to repeat. Sure made a mess of the shop! Ended up throwing most of my clothes away becuse of all the oil stains. The air boxes tend to load up on old worn out detroits when they get idled to much. Put a rebuilt motor in the Drott with the shutdown valve, and I checked all of the rest of the GM diesels for that valve.

 

[R.E. Miller]

Good stories!

Recently at work I was running a 8. 3C on the dyno, the shop foreman wanted to know what the boost pressure was. I didn't have my guage working, so I borrowed one. Didn't think to ask what the guy was using for before me. Just an innocent little pressure guage with a cummins compu-check fitting Hooked it up, powered down steady for first pull... . let off, rpms go into bark/hover mode then in a drowsy fashion, the engine returns to idle. Turns out that my buddy had used his guage right before me to check fuel pressure and it had a 10' / 3/8" hose on it. Yup, hose was clean, and I laughed after I figured out what happened.



Russell

 

[QRTRHRS]

Not exactly the same but....

Working on this vacuum asisted piece of equipment. It has two gated ports, one for the main pump and one for a turbo pump. Pumps were running to put vacuum on the forelines, one of which had a slight leak. By mistake, we opened the turbo port. The port had a particle screen which immediately disappeared but not without protest. So much for that turbo. So much for our shorts too.



BIGDIG, I have seen TV shows about that project. Takes a special breed just to go down into that hole.

 

[JWhitcomb]

RThompson,

What is "running the rack"?

 

[BIGDIG]

Re: Not exactly the same but....

Originally posted by QRTRHRS





BIGDIG, I have seen TV shows about that project. Takes a special breed just to go down into that hole.

It's all about the diesel fumes... . Oo.

 

[illflem]

running the rack

Seems like RT has a different meaning for it but I've always heard it used as a pool playing term meaning to hit all of your balls in after racking up and breaking without the other player getting a shot.

 

[GWHaley]

since these are somewhat funny stories....

Thought I'd add an engine running backward story (even though it's not diesel).

I had a '77 KTM 400 motocross bike that would start up backward from time to time. The first time it happened to me, I noticed like the others that it was running rough. I let out the clutch and it started to move backward. Really not a problem, it was fairly easy to tell when it would do it.

I finally decide to sell it and the guy that bought it put his 16 yr old kid on it for a race. Now the kid has been racing for some time, just not something this big. He gets up to the line and starts it, the thing was running backward and he didn't realize it. The gate drops and guess what... yeah, right over the bars he went!!! :{

 

[RustyJC]

Running the Rack

On our diesel and dual-fuel engines where each cylinder has its own fuel injection "jerk" pump driven off its own cam lobe, the engine is balanced by adjusting each pump individually to produce equal peak firing pressures at a given fuel rack position. This is done by adjusting the link between the rack and the jerk pump while measuring that cylinder's peak firing pressure with an engine analyzer, Bacharach indicator or similar device.



Another procedure sets maximum engine load by adjusting the rack stops - mechanical stops that limit maximum travel of the rack. DEMA (Diesel Engine Manufacturer's Association) engines are rated for 110% of rated BHP for 2 hours out of every 24 hour period. This is done initially on the test bed where the engine is loaded to 110% load and the rack stops are set at that position.



The overspeed governor on large industrial diesel/dual-fuel engines (e. g. , Cooper-Bessemer LSVB-20-GDT) is linked to butterfly valves located on each bank between the aftercoolers and the air manifolds. When the overspeed governor trips, it slams these butterfly valves closed, thus shutting off the air supply to the engine's cylinders.



Rusty

 

[JWhitcomb]

I know the pool term but have heard people talk about racking in some sort of matainence procedure.

 

[me4osu]

Originally posted by JWhitcomb

RThompson,

What is "running the rack"?

On 71-series detroit diesel engines "the rack" is a long tube that runs the legnth of the head and is supported by bearings. One end is connected to the governor and there are adjustable levers that drop from the tube. When the gov. turns the rack, each lever moves a linear "rack" gear that meshes with a pinion mounted on the metering valve for each individual fuel injector. Much like RustyJCs engine, the plunger is operated by the camshaft.



"Running the rack" is adjusting each lever so that there is equal clearance between each lever and metering valve rack. This ensures equal fuel delivery to each cylinder.



Air stops should be used as a last resort AFTER the fuel supply has been positively shut off. We would always start the old detroits, after overhaul, with a pair of vise grips on the rack, so that we could override the governor. Also, the old engines had external fuel supply tubes that you could smash with a hammer to "positively" shut the fuel off. If the air-stop is pulled first, the engine has a tendency to suck the blower seals in and run on lube oil.

 

[Champane Flight]

Old days

In the old days the 71 series detroits would always run better if you "Ran the rack" after getting the engine as hot as possible. It would always tickle me to see guys doing this on the top of Monarch pass, or some other mountain pass with burnt fingers and oil smoke rolling off the exhaust manifolds.

 

[RThompson]

Well here is a try at describing what 'running the rack' on a Detroit 2 stroke is about. Keep in mind that Detroits don't use an injection pump, they do have a small low pressure pump on the back of the roots blower that supplies the unit injectors with fuel. Inside of the valve cover the cam operates the exhaust valves (2 or 4 depending on engine model) and the cam also pushes the unit injector to provide the timed high pressure fuel injection. Each injector has a geared rack that ties it to the governor and throttle. This mechanical linkage all has to be set to provide an equal stroke on the injector. Not getting a motor up to temperature before doing this makes it hard to get a good running motor. It is always easy to tell when a detroit diesel has a good tuneup as there is a distinct crack in the exhaust when throttle is snapped open.

BTW, Detroits have been around a long time without many changes. The 71 series started back in the late thirtys and was not changed much for 60 years. They went from 2 valves to 4 valves and added a turbo on some of the high output engines. One of the odd ball engines that was made up from the 71 series was a 1 clyinder that was used on gen sets during WWII.

 

[FFutch]

Unit electronic injectors and DDEC was the best thing Detroit did on the 2 strokes,eliminated the rack completly. O. K. all you Detroit experts,what is the clearance on a 92 series intake valves ???A cookie to the first one with the right answer... Doug

 

[RustyJC]

-53, -71 and -92 series Detroits are uniflow 2-cycles. They have intake ports and exhaust valves. No intake valves.



Rusty

 

[HillCountrykid]

You owe Rusty a cookie.



I did'nt catch that one.

 

[FFutch]

That was quick . What'll it be Rusty,Oreo or chcolate chip . I do catch alot of guys on that one though,some even go to the manual to look it up ... Doug

 

[RustyJC]

Nice, hot homemade chocolate chip cookies would be nice!



Rusty