A Detroit 500 engine riddle, can it be solved

I'm no mechanic, but this is my theory. When the turbo failed, you lose boost. Where does that boost go? It goes into the intake. When the turbo is replaced and oil is in the charge air cooler and from the story, the truck was started up and idled find. How much boost is there at 600 RPM? My guess little to none. BUT, when the throttle is raised the turbo spools up and my guess air from the turbo has enough force to PUSH oil into the intake, the oil begins to fuel the engine and the engine picks up speed and so does the turbo, more oil gets burned with the suction/boost the oil gets sucked in. That is my theory, is it true? Who knows. Without a doubt, after a turbo fails the CAC maybe full of oil and not run away. BUT, explain why it is when the new turbo is installed that it runs away? I think I nailed it.

 

my old 2 stroke, if i let er idle too long, it revs up to a very high rpm(pant crappingly high!) until it burns off whatever is leaking into the intake. usually for about 6 seconds then it goes back to normal. i might put in a intake, emergency shutoff valve like they use up north in h2s situations . when screaming at these high rpms, the pull shutoff wont even work. if i high idle it or rev the crap out of it for a bit, it does not do the rev thing.

 

Sounds to me that no one cleaned the charge air cooler out from the old turbo passing oil into it so when it finally made its way through the engine started running away on the oil happens all the time when you lose a turbo going down the highway I would wanna know why they dident clean out the cac and also why dident the mechanic leave the intake off and have a 1/4 steel plate with a handle ready to cover the turbo inlet just in case I leave it off and have one ready to any time I start a new engine or do any kind of major engine work I've never had it happen to me but if it does I wanna be ready

 

I have seen many engine, from every manufacturer, with the CAC full of oil, to the level of the intake, to the point it shuts the engine down, Never, not once seen an engine run away from ingesting oil. I did engines for 40 years, 2 cycle Detroit's, naturally aspirated Cummins and Cats to the latest computerized units. The old Cummins would rev up but not blow up, The old single and double disc Cummins were a scary pieces to work on.
Being in BC we get units that are pulling their guts out, and then have a problem, when they ingest oil, they slow down as the oil preignites, uses the oxygen in the cylinder and the fuel that comes in at the right time has no oxygen to burn.
It is a great wives tail just does not happen.

 

But on the other hand, I have seen it happen. I have had it happen to me while driving. Not in a truck, but in an automotive diesel. The factory came out with a different crankcase ventilation system to keep the engine from sucking the oil into the intake, which stopped the problem.

It's fun going through town when the engine takes off by itself and overrides the brakes.

These engines wouldn't do it from idle, but at a medium rpm on up.

 

I'm sure Elliot/Wilson Peterbilt's mechanic thought the same thing after replacing a turbo that oiled the aftercooler..........until he started the Cummins ISM engine in a Fairfax County VA firetruck. The truck was sitting outside the shop foreman's office when the engine took off. Maybe you'd like to talk to him, his name is Steve Doyle, he is the shop foreman at the Landover MD Peterbilt dealership now. At the time of the incident he worked at their Manassas VA dealership. I'll make it easy for you to contact him with a toll free phone number 800 787-9000. I'm sure he hasn't forgotten about it after buying the county a new engine, because of a lazy mechanic not bothering to check the aftercooler for a large amount of oil and cleaning it out while on an hourly work order. That was a very expensive lesson that a mechanic learned the hard way, fortunately for him it didn't come out of his pay.........wives tale my azzzzzz

 

I spent 10 years at a Detroit dealership, and we had engines that got a sniff of Gas, Natural gas in a diesel above 8% will also preignight. They all had a Barber rig saver, and the reason for that was to reduce the possibility of fire not to protect the engine.
I saw lots of engines in the dyno room that had solvent in the Air box and it would rattle when taken above idle. Never ran away. We built Natural Gas motors out of 8V71s. Many truckers run propane as a boost in their engines, as long as it is kept below 7% they have no problems.
Motor oil burns quite well as does bunker C which is nearly asphault. You have seen ships, most of them run on Bunker C.
All the new Diesels run the breathers into the intake, Detroit had the 8.2 they took the breather out of the intake in the early 80s because the injectors leaked fuel and the engine sounded like they were coming apart, pre ignition.
We were the engine dealer never had one come apart.
Natural gas engines have lower compression ratio's if they did not they would preignight. I worked on and built duel fuel engines, they run gas as a fuel at 7% and diesel as the ignition source, and the power part of the engine operation.

 

every once and a while if i don't idle up my 8v92, it will do a runaway thing for bout 6 seconds when i give it a rev. seems to only do it if i let it idle for 10 minutes or so without idling it up. Is that my turbo ? it it rather frightening when it runs away. thanks

 

Check your air box drain tubes and make sure air is coming out of them during idle. If not, take them off and look at the check valve. The tubes or the back of the air box may be full of crud not allowing the oil and excess fuel to drain out of the tubes.