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Author Topic: ST3 engine. Diesel getting into engine oil  (Read 12637 times)

forestlander

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ST3 engine. Diesel getting into engine oil
« on: May 20, 2007, 06:11:55 AM »
I have a lister ST3 engine as part of a 15kva genset. When I bought it it was reputed to have done only 20 hours running. Subsequent examination of engie parts suggests that this may well have been true. After around 100 hours use, I noticed the oil start to creep up the dipstick, and sure enough , diesel was getting into the oil. Checked all the usual things, loooking for cracked leak-off pipes, leaking injector pipes, changed the lift pump diaphragm, had all the injectors serviced. Still the same.Started to suspect an individual injector  pump lower seal The engine was running a bit rough, and by 'cracking' injector pipes and using decompressor on individual cylinders, found the cylinder nearest the fly wheel was the rough one.
No choice now but to strip and look. The whole head was coked up on the exhaust side, with the exhaust manifold aperture almost closed off with very hard carbon. (got a small cupful out). Rings were completely free, valves in good condition, (just a bit of work needed due to carbon build up causing sticking, but only to be expected). Wear-wise, everything in virtually new condition.
Looking at the common exhaust manifold, the cylinder aperture nearest the flywheel again, nearly closed off, the others with a bit of build up but not excessive.
Any ideas about this one any one? Haven't looked at the other heads yet, but will have to. In the meantime having to use my original 3kva lister single cylinder genset to charge my battery bank of 900 amp hours, which I can normally charge at an nitial rate of 150 amps.

dieselgman

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Re: ST3 engine. Diesel getting into engine oil
« Reply #1 on: May 21, 2007, 05:14:47 AM »
I have seen delivery valves leak fuel out of the injection pumps. This problem with internal fuel leaks is well known on these models, usually it will be related to fuel lines. We often replace them with new when overhauling the engines just to be sure. The coking on #3 could be any number of things but most likely - injector nozzle. I would recommend servicing all fuel pumps carefully and then you could swap injectors around to see if the problem moves with the injector. Pay close attention to cylinder crosshatch and ring condition, #3 may have ring seal issues as well. What kind of crankcase vacuum did the engine have when the unit was running? The Lister S Series Service Guide goes into detail about the internal fuel leaks.

You can email me if you need more specifics on this model.

Best of luck!

Gary
diesel-electric.us
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations

forestlander

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Re: ST3 engine. Diesel getting into engine oil
« Reply #2 on: May 21, 2007, 07:54:41 PM »
Thanks for the reply. Injectors are all done now.
 Could the coking cause neat diesel to get down past the rings if combustion not complete? Trouble is, don't know which is cause and which is symptom. would like to get to see that bit of the manual about fuel leaks.

dkwflight

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Re: ST3 engine. Diesel getting into engine oil
« Reply #3 on: May 23, 2007, 02:26:52 AM »
Hi
Dribbling injectors can do what you experienced.

What temps are you running the engine?

Maybe not hot enough.
Dennis
28/2 powersolutions JKSon -20k gen head
Still in devlopment for 24/7 operation, 77 hours running time

forestlander

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Re: ST3 engine. Diesel getting into engine oil
« Reply #4 on: May 25, 2007, 09:05:32 PM »
Thanks Dennis,
                      Injectors were my first thought, and I did them all before I finally stripped the head off.
Of course, with cylinder 3 exhaust manifold already reduced to pencil width, the serviced injector would not have made much difference. Rings and cylinder are all OK, so I'll clean it all up, put it all back and try again.

dieselgman

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Re: ST3 engine. Diesel getting into engine oil
« Reply #5 on: May 27, 2007, 11:23:38 PM »
If your cylinder walls are glazed and rings not sealing properly, then that cylinder can allow fuel into the oil. This is surely not the top of the list of possible culprits though and generally an effect rather than a causative factor. Good luck on your "clean-up", most of the time this is all that is needed.

Gary,
diesel-electric.us
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations