HELP! fuel contamination in oil

[atlowers]

Just had results of an oil sample which has returned a warning on FUEL dilution to the oil..
Have been advised that the engine oil should be changed immediately. And the source of fuel contamination located and rectified. Analyst suggests Fuel contamination of the oil may be from a Faulty fuel lift pump or Injector pump seals leaking fuel oil into the timing case.
Trouble is I have run the engine for 6 hours since the sample was sent and have had a clogged pre filter problem which caused loss of speed but am really worried about any damage I may have done running her with the contamination. She ran fine until the clogging and after changing the filter but can anybody iether calm my nerves or send me into orbit with the possible consequences and advise on other possible causes of the contamination.
Thanks
Andy

 

[fisherman]

Not too much of a problem IMHO. Diesel fuel is a reasonable lubricant, trouble starts when you have so much in the sump it goes up past the piston rings and runs the engine, which then cannot be stopped.......Sounds like you didn't get that far.
I always rub the sump oil between my finger and thumb when checking the dipstick for this reason.

 

[Solitaire]

Andy - contact Bill Brown at BBMS - he is all man Yamaha. 07802 290840.

 

[oldgit]

One other possibility.May well be worth testing the injectors before serious dismantling takes place.
Oil dilution in fishing boat diesel proved to be nothing more than faulty injector pumping neat fuel into the cylinder.The engine had just been rebuilt by workshop with excellent reputation and it was removed and rebuilt twice before problem was traced.Funny thing was the engine apppeared to run normally under load.The sump oil level would rise during any trip out.

 

[Bilgediver]

It wouldn help if you confirmed what engine it was so we knew what we were discussing. Some small engines have their fuel pumps inside the crankcase and so these are a source of fuel dilution when worn...some modern diesels have a high pressure fuel pipe running round the timing case to cam timed injectors and these pipes can fail at the connections and leak.

also as one other has said the fuel lift pump if fitted to the crankcase can be a source if the diaphragm fails..

You must change the oild and even flush too as well as identify the leak.

John

 

[atlowers]

Bilgediver, thanks for the reply, its a yamaha 370 me370 sti 165hp. How would I identify the source, would the diaphragm be obviously faulty and also do you know how I check the injectors. Also is it ok to run the engine at all before sorting or would I be doing major damage.
cheers
Andy

 

[Wiggo]

we had exactly that problem last year - 4 injectors hosing neat fuel. The oil level in the sump rose dramaitcally, and at low speed we were leaving a huge smoke cloud, but she ran fine at high revs. All cured now, though.