1978 yanmar 2qm20 fuel in oil. from gear and maint forum

AUBERGINE · #1 (**permalink**) 07-14-2009

over past year fighting a problem with fuel getting in oil, the latest is....

pulled the inj pump took it to a shop, they said "bad seals, bad plungers, should be the problem", tested the injectors the old ones were still good. got inj pump back, put it in, starts better, sounds good, planned a trip.

took boat out this weekend to santa cruz island (great trip!) ran motor for about 5 hrs, and as im getting ready to enter anchorage cough, chug, i shut it down, started the evinrude on the back, got anchored, checked the oil again and darn, its full up the dipstick again. It appears the problem is still continuing.

so any old school mechanics got any ideas, i have replaced lift pump, injectors, and injection pump, the 3 areas the fuel would be entering the oil from, i changed oil and got almost 3 gallons out of it. thin. supposed to have 5 quarts, i will be watching, monitoring level, ran it for about an hour after changing level seems ok, seems to take about 5hrs to come up the dipstick.

any other areas to go after where fuel would be entering oil?

thanks
scott

timebandit · #2 (**permalink**) 07-15-2009

I would go with another lift pump, sometimes a new one can be bad..

You could install a electric fuel pump on the fuel tank and remove the lift pump but keep the hoses connected and run the electric and see if the lift pump is leaking through the diphram or somewhere else.

timebandit · #3 (**permalink**) 07-15-2009

On a side note.
The lift pump should be able to pull through an electric fuel pump with out it running so that you can just run it to help bleed the system and then turn it off and allow the engine to run on the lift pump.

AUBERGINE · #4 (**permalink**) 09-09-2009

problem still persists. rise in oil level from fuel entering crankcase from somewhere. i have replaced lift pump with new, and had injection pump rebuilt (shop said seals were definately bad), and new injectors. had boat out again and after about 6hrs CLAK CLAK CLAK shut down engine and oil level is high, pulled out the same amount almost 3 gallons of oil. normal is 5 qts.

2 mechanics have said after after changing the 2 pumps problem "should not be happening". diesel shop has offered to retest the 2 pumps. Has anyone had experience with this? are there any other areas where fuel would be entering crankcase?

need to get this problem solved so i can move on to all the other problems on my boat.

thanks
scott

Faster · #5 (**permalink**) 09-09-2009

This is a strange one.... that's a lot of stuff getting into your crankcase... on our non-yanmar the injection pump is completely independant of the crankcase/block so I'm having trouble visualizing how that could be the source.

The most direct route for fuel into the oil sump would seem to be via the combustion chamber, past the rings and down the cyl walls - but that would mean one cylinder wasn't firing and you'd know that in a 2 cylinder engine right away.

Failing all that the only other thing that comes to mind (that would pass that kind of volume) is the return line that should be going back to the fuel tank.. way out in left field, I know, but by now you must be looking out there...

AUBERGINE · #6 (**permalink**) 09-09-2009

when i took out the injection pump it is sitting in a oil bath inside the engine, this location along with the analysis from the diesel shop, i really thought there was the problem. however, had the boat out again last weekend and it persists.

regarding return line this engine has the return line going back to 2nd filter back in the system from there, not the tank, dont think that would be source. i talked about the rings with mechanics and both were consistant with you faster it would be one cylindar and i would know it.

next suggestion?

timebandit · #7 (**permalink**) 09-16-2009

Ok, I will go way out on a limb and make some assumptions.

This boat has been yours for over two years and was running fine and this problem just started a year ago.

You did NOT buy this this boat with this problem.

If either of these statements are NOT true I would look at
"regarding return line this engine has the return line going back to 2nd filter back in the system from there, not the tank, dont think that would be source."

This set up bothers me because usually the return line has little or no pressure because it dumps into the fuel tank.

The current setup requires that the return line work aginst the head pressure of the lift pump (5-8 psi) and may cause a seal that works under zero pressure to leak when installed but not on the bench. A pluged filter on this line could also raise the pressure.

Personally I would route the return back to the tank.

If however the above statements are TRUE then you must bypass the lift pump (hose around) with a electric and eliminate the lift pump from system and test.

No increase in oil then you have found the problem--the lift pump.

Still getting oil increase then it is the injector pump since I cannot see the injectors running that much fuel by the rings and the motor running without looking like a stink potter.

Let us know how it works out.

AUBERGINE · #8 (**permalink**) 09-17-2009

this is my 3rd winter with the boat, engine had not been run since mid 90's due to throttle cables breaking and PO not fixing it so it sat in a slip all this time. i put an outboard on her which works ok but i wanted to learn about how the engine works. I didnt know anything! I got the manuals and sonofabitch after i replaced many of the rusted parts ... got her going and this problem is the last one that persists.

thanks for the sugestions, my first step is going to be to pull the inj pump again and have it testd at the diesel shop. i remember after servicing it they had my fuel lines upside down and i may have loosen something when i turned them back right side. then i will see if lift pump is problem. im not sure how to bypass lift pump, i have the old one still, i was thinking to shear off the cam lever so it wouldnt pump and then run new hose from electric pump to 2nd filter, but i havent figuered if it will work.

diesel shop says got to be one or the other wouldnt be fuel return line as it has no access to the oil.

ill post how it goes.
scott

timebandit · #9 (**permalink**) 09-17-2009

Just connect the line from the tank to the electric fuel pump and then to the filter by passing the mechanical lift pump altogether and the chance that the diphram is leaking fuel into the engine.

The mechanical lift pump does not need to be removed since once you remove the fuel feed it will just pump air, you can just put a fuel line from the intake side to the pressure side to keep it quiet if you want.

" then i will see if lift pump is problem. im not sure how to bypass lift pump, i have the old one still, i was thinking to shear off the cam lever so it wouldnt pump and then run new hose from electric pump to 2nd filter, but i havent figuered if it will work."