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Old 15-03-2011, 15:13   #1
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More Yanmar compression problems

Hi

I have a Yanmar 4LHA-STE turbo charged and inter-cooled engine rated for 230HP

and I am getting diesel fuel in the engine oil to the extent that it is thinning the engine oil considerably.

I also have very low compression on 2 of the cylinders (120psi) at idle speed of 600 rpm the other 2 cylinders show 240 psi. The fuel lift pump has been checked and appears to be ok.

What are the likely causes of fuel getting into the engine oil ????????

A list in order of probability would be helpful in trying to locate the problem
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Old 15-03-2011, 15:33   #2
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Re: Yanmar Engine Compression Test Values

Raw fuel in the engine oil? The pump is the most likely suspect, so consider checking that twice.

I wonder if the injector pump's internal area has access to the crankcase in the event of a malfunction? Could be similar to the lift pump in that it has an internal proximity to the crankcase. I can't think of any thing else where fuel can reach the crankcase.

I've built gas engines, but diesels are new to me.
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Old 15-03-2011, 15:50   #3
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Re: Yanmar Engine Compression Test Values

" 2 of the cylinders (120psi)... the other 2 cylinders show 240 psi."

Time for a rebuild. Cylinders, rings, head, head gasket...in any case the engine has to come apart and everything evaluated once it is open. Unless you're up for a rebuild job, it is time to find a pro and let him take over.
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Old 16-03-2011, 17:30   #4
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Re: Yanmar Engine Compression Test Values

Quote:
Originally Posted by hellosailor View Post
" 2 of the cylinders (120psi)... the other 2 cylinders show 240 psi."

Time for a rebuild. Cylinders, rings, head, head gasket...in any case the engine has to come apart and everything evaluated once it is open. Unless you're up for a rebuild job, it is time to find a pro and let him take over.

^that
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Old 17-03-2011, 03:55   #5
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Re: More Yanmar compression problems

Fuel in the engine oil -- usually lift pump diaphragm is leaking.

How many hours on the engine?

Sounds like the engine is well knackered. Probably from running it without lubrication (lube oil too much diluted with fuel).

Sorry.
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