Low RPMs and Smoke

[shakey doug]

Charlie, A marine engineers-- Nose , eyes & ears are his best diagnostic tools. Place sump oil sample on palm of hand and sniff, recommend Nose for this one. Place sample of sump oil and new top up oil side by side on a dinner plate oils must be at same temp then incline plate to 30 deg the diluted one will be evident, recommend eyes for one. Shhhhhhhhhh.

Doug.

[Charlie]

Hi Everyone:

I have a question for you in regards to the Yanmar 4JH4E. I had a problem with the engine when I came out of Cabo San Lucas the other day. It started smoking (white) a few minutes after I left the fuel dock. I shut the engine down and began sailing. I anchored the boat and looked at the fuel filter and there were some large particles of gunk in them. I had to take apart the racor 200 in order to clean them. I did not have a new O ring to replace the ring in the filter housing so I used the original. The old O ring failed and that is why the engine died. It was a major air leak. I changed to my alternate Racor and the opposite fuel tank and everything worked fine for about 6 hours. Then the engine began racing and the white smoke came out again. I changed back to the first racor and the engine died. I used the dink to limp into dock. From there I removed all the fuel from the tanks, put it in Jerri cans, ran it thru a Baja filter and then returned it to the tanks. There was nothing particularly dirty about the fuel and the baja filter did not have any water in it when we were done.
The next day we ran the engine slowly under 2000 rpms. When we brought it up to the cruisng speed (2200 rpms) it started spitting out smoke. We dropped it down to 1200 rpms and the smoke decreased then was completely gone. We brought it up to 2000 rpms and there was no smoke when we brought above 2000 the engine would race and then it would smoke.
I pulled about a quart of oil out thru the dipstick and then we could go up to 2100 but not above or the engine would smoke.
In reading the manual I studied it and found out that I have been putting too much oil in. I have been putting in 5.5 ltrs and when an engine is set at a rake (as mine is) it should be 5.0 ltrs. When I arrived in La Paz I went to change the oil and I extracted almost 8 quarts of oil. The oil smelled different but still had reasonable viscosity. Now I know that I didn't put in 8 quarts of oil so I am trying to figure out how come there was so much oil in the crankcase. These are my theories:
1) possible water in the crankcase -- the oil was not milky and had a reasonable viscosity so I doubt this)
2) Perhaps the suction device that I have been using has not been extracting all the oil from the crankcase and the too much oil problem has compounded over the 3 or 4 oil changes that I have done. -- A possibility but on my last oil change I had to remove some oil after I had changed the oil b/c I had added too much. The oil that came out was dark for a little while then I got to the clean oil. It was filled to the top line of the dipstick.
3) Somehow diesel is getting into the oil. I read on CF that this has happened to someone with a Yanmar 3GM by leaking thru the injection pump and was wondering if it could happen on a 4JH.
Do you have any other ideas? The boat is in Mexico and I wanted to bring an oil sample home to have it tested but I was afraid the airlines wouldn't let me bring the oil on the flight so I didn't do it.
I changed the oil and added back only 1 gallon of oil and the dipstick read that the oil was over full. I ran the engine for a few minutes while moving among the docks for maybe five minutes and when I read the dipstick again it still read over full at the same level as before I ran the engine.
I plan on bringing the boat back to the US in the spring or the summer. Parts for Yanmars are difficult to get in Mexico although I am told there are some real good mechanics.
so if this is something that I need to take care of right away -- and I imagine it is -- I would need to bring parts with me from the US and then go to Mexico.
A friend is borrowing the boat right now and I have asked him to check the oil everyday a couple of times and if the viscosity gets thin to remove some oil and add fresh full oil and then to motor as little as possible.
Do you have any ideas?

[captden]

Charlie:
I had the same problem with the 4jh on my last boat. I was using the main engine a lot , at a little above 1200 rpms to charge the batteries and one night when I went to shut it down it did run away, long story. Anyway what I found out with mine some leaking injectors and the excess fuel was getting into the oil. I bought new injectors and never had any problems after. Made sure on this boat to be able to charge batteries off main engine unless underway.

Hope this helps
Captden

[Charlie]

Thanks Capt that is a help. I am not a good enough mechanic (well good at all LOL) to be able to figure out where diesel could be leaking into the oil supply from.

[mike d.]

don't know what your engine looks like but if you have your fuel rail under the valve cover the rail could be leaking. i can tell you this i had this happen on a new 350 Cummins i had in a truck in 79 and it was what they call making oil because of this condition. they found a crack in the rail and had to rebuild engine. this is not something you want to let go, and yes you should be able to smell the fuel in the oil. take sample from the engine and one from the bottle (fresh). smell fresh oil first and then smell the crankcase oil you'll be able to tell right off. you cannot just empty down to full mark. the fuel is thinning the oil and and will not give the lubricity the engine needs. remember that a marine engine works harder than an automobile motor. you may be damaging your engine

[delmarrey]

Here are some pictures. There are no seals in the injector but if the assembly were not screwed together tight then fuel could bypass the nozzle and on into the cylinder.
There is one other path that the fuel could take. It's a lube oil line that's attached to the pump from the block. If the fuel is under pressure and the pump leaking internally, it could be backing up into the oil system via this line.



.................................._/)

[captden]

Mike is right the oil does get thinner, also I should of mentioned the reason mine ran away was the high oil level creates a lot of pressure and the oil was being pumped through the air intake and the engine was running off this. When I pulled the air cleaner off oil shot out of the intake and the engine stopped. Trust me you don't want to have a run away diesel. I would correct the problem before using the boat, and do a complete oil and filter change.
Captden

[Charlie]

Del:

Thanks for the info I will study up on this and see what kind of tests that I can run to figure out this problem.

CaptD:

I see your point. I did a complete oil change. I did not resolve the problem though. I now need to figure hout how to find out how the fuel is making it in to the oil. Hopefully I can figure this out. Del's post is a great place to start.

[Chief Engineer]

Leaking diaphagm in the fuel lift pump