desiel in the oil.

AUBERGINE · #1 (**permalink**) 02-03-2009

i have a 2 cylindar 1978 yanmar 2qm20. while motoring suddenly clak clak clak rpms bog down, white gray smoke, then passes and rpms come back up, few minutes later same thing.

checked oil at the dock and it was filled up to dip stick. some oil mist came out of intake. oil black and very thin, smelled a little burnt no evidece of water. changed it out got 3 gallons after about 5 hrs motoring off and on. started motor again sounded ok , not a lot of change in oil level after an hour running.

mechanic took a listen and seemed to think fuel was coming from high pressure pump.

question is where could the fuel be coming from? any other checks / advice would be appreciated.
thanks
scott

boatpoker · #2 (**permalink**) 02-03-2009

?? from the high pressure pump thats what it does. Are you suggesting there is fuel in the oil ? Sounds a bit like overheating. Do you have a temperature guage and what does it show. Need a lot more info

SteveInMD · #3 (**permalink**) 02-03-2009

It could be the high pressure pump, or just the lift pump. I'm not super familiar with the 2qm20 but if it has a mechanical lift pump the only thing separating the fuel from the crank case is a rubber diaphragm in the pump. The lift pump would be much cheaper to fix than the high pressure pump so you should hope it's that one. You can test it by removing the pump, then put a few psi of air to the inflow side with the outflow blocked. You should be able to tell if the diaphragm is leaking. If it leaks replace the pump. They are pressed together when built and are not repairable.

AUBERGINE · #4 (**permalink**) 02-03-2009

Im sure its not overheating, to fuel is entering the oil from somewhere and i am trying to narrow the sources.

i think steve you are on right track, didnt know the a bad diaphagm would allow fuel into the crankcase, the engine had been sitting unused for years by PO. probably both lift pump and high pressure pump are bad. any other way to test high pressure pump? any other sources ... how about fuel injectors, ?
thanks
scott

SteveInMD · #5 (**permalink**) 02-03-2009

You wont get fuel in the crankcase via the injectors. I think the lift pump is actually a much more likely source than the high pressure pump. The lift pump will cost you $100 or so for the part (varies somewhat by motor). The high pressure pump will be big $$. I would hope for best and start with the cheap one. I think if your high pressure pump were bad you would be low on power. Eventually the motor wouldn't run at all.

The noise you described could just be a slug of air entering at the lift pump.

Some people put a electric fuel pump in line before the lift pump. I think this is a bad idea because a hole in the lift pump diaphragm will allow the crank case to be pumped full of fuel by the electric pump. When you get enough diesel in the crank case the motor will run up to max rmp an stay there. The only way to shut it off is to block the air intake or shoot a CO2 fire extinguisher into the intake.

AUBERGINE · #6 (**permalink**) 02-03-2009

thanks steve i did talk to a fuel injector shop and they would test and replace seals on high pressure pump for $250. and check injectors for free but injectors are in there tight (and rusty) and im reluctant to dislodge them.

i will do the lift pump first, sounds practical, keep an eye on oil level. the noise was a very ugly clak clak cough cough. maybe because of oil level so high? also mist of oil spit out of air intake.

i have a temporay outboard tank with a hose with bulb to pressureize the system. works good to bleed it. but if the tank is below fuel lift pump it runs dry. otherwise i would need an electric pump as you described.

sailcapt2 · #7 (**permalink**) 02-04-2009

Had the same problem with my old Perkins. You can always cap off the lift pump and put an inline electric pump. That will eliminate the lift pump. If you are still having problems, then you will know that it is the high pressure pump.

Rockter · #8 (**permalink**) 02-04-2009

Steve :

Good point about the perforated diaphragm. Perhaps I should by-pass the engine lift pump completely? I could put a wee fibre-optic light on the pump and feed it to the helmsman. That would not be a big job, really.

Pressurised fuel has its risks, but man does it improve the starting and fuel reliability.... not one single rev drop in 15 years.

Excessive mechanical noise is a very bad sign. I hope he has got away with it. It does sound like the lift pump has perforated. I will check the Volvo pump to see if that could happen. I suspect it could.
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timebandit · #9 (**permalink**) 02-04-2009

The diphram is shot that is why the fuel pump won't pull fuel from the tank.

The clacking was from the pistons slapping the oil on the down stroke.

Change the pump or block it off and install and electric but with the electric you loose the ability to run without 12 volts.

Be sure to change out the diluted oil after you change the pump, and the filter.

Rockter · #10 (**permalink**) 02-04-2009

Yes, I guess that would be the clacking sound. The pisto skirts must have gotten a hard time. Still, it might be OK.

I will remember that one. If it happens, I will know to shut off, and stay shut off until I solve it. With an electrical charge pump, I could by-pass the lift pump to get me home. That oil will need a change on the spot though. It will be thin and easy to pump I expect.

It will be Seasick City trying to do that in even a mild sea.
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