3YM20 Yanmar Death

[dlockhart]

Was heading south on the Gulf of Mexico for a day or 2 with little to no wind so both engines were running easy both smoking a bit which I attributed to 1/2 tank of last years fuel mixed with fresh stuff. The starbord engine began putting black smoke out, not alarming amount, and soot in the water then slowed down and quit. Having had hands on everything except anything relating to fuel I figured it starved for fuel and died so I removed the primary filter and sure enough it had a large wad of black bio looking stuff on the top so I changed it and pulled the Yanmar filter off and it had seperated the bottom steel plate off at some point so was basically useless. It was changed and the engine hasn't run since. I bled the filter housing, the banjo fitting on the inlet and outlet to the injector pump, the outlet to the line at the pump and the injector and it seemed to want to try to start on 1 cylinder. I thought some goo must have made into the other injectors so I removed the injectors and the inlet looked fine, I sprayed brake clean through the lines and return line, all fine, I rolled it over and seemed to get fuel out of the lines so I put back together and bled it all again with no results. I removed the injectors and assembled the lot off to the side and with no injectors in the engine rolled alot quicker without compression and I got nothing at first then seemed to get spray out of the injectors. At this time I stuck my thumb in each of the cylinders and rolled it and each seems to have compression. I think it must have been airlocked so I reassemble, bleed and glow and it seems to want to fire on one cylinder at first with a second joining now and then but will not start. A lot of turning over so I unhooked the exhaust so as no to flood the engine with sea water. It always started just by thinking about it. I am missing something or barking up the wrong tree all together as the other engine is running fine on the same fuel and filters??? Was supposed to meet daughters in the Bahamas but fear heading over to even more expensive parts on one engine.
Any ideas would be appreciated and if anyone knows of a good diesel mechanic with more tools available than I have in the Keys, that would be appreciated as well.

[Charlie]

NO real ideas except am troubled by the Yanmar filter bottom plate. Are you saying that the filter itself was bad or the place where the filter is attached. Could it be leaking air into the system through the filter? Are you saying that you only have one tank? Have you thought of taking a jerri can and filling it with clean fuel and running this through the primary filter and bypassing the yanmar filter. I would run it as a gravity feed bypassing the lift pump. If that works you will narrow down the suspects that can be problems. From there move the input for the fuel back downstream (eg thru the lift pump but not the filter next the filter etc.)

Upon re read I would start by looking for holes in the fuel lines first especially around the hose clamps. Sometimes these will let in enough air to stop the engine from running.

[DotDun]

FWIW, I hired a diesel mechanic when I couldn't get an engine started after a filter change. I watched him bleed the injectors for about 1 minute longer than I did. Engine fired right up!

Lesson learned (and paid $85 for): Patience!

[dlockhart]

Charlie: Filter element had seperated the steel plate from the plated filter. Have been frigging with this thing for 2 days, wish I had a compression tester to be sure of that other than the thumb test. At a loss, have to think about it some more.
Thanks for the replies.

[dlockhart]

Sorry, seperated the steel plate from the pleated paper element.

[gjordan]

Not clear if you have separate tanks for the engines, but if you do, recheck the primary filter to see if you have so much muck in your tank that it immediatly plugged up again. I did a delivery once where the engine quit 20 minutes out of port , changed filters and it quit an hour later. Tank was full of Algea. Lousy delivery.___Grant.

[dlockhart]

Okay so a lot of back to basics head scratching, everything seems to be right, good spray from injectors while assembled outside the engine, compression feels ok but again I have no compression gauge here with me and although everyone I spoke to says that if you have good injector spray then it should start so you must have bad compression on 2 cylinders if it is trying to start on one. For the life of me I did nothing to cause piston or ring or ring land failure from the point of running well to not running, no ether, wd40, gas or overheat, over revving or any of that stuff so I'm not convinced of the compression theory. I called Frank at Marine Pro in Cocoa, Florida who helped me out before with engine trouble, (321-636-8950) and whom I get all my Yanmar parts from as they are an A dealer and get good pricing, and I told Frank everything I've stated here including the doubt about the compression problem. I asked him if carbon could cause anything like this as that is all that was different, the engine was making a lot of soot and black smoke due to the plugged fuel filter, he asked me where I had the exhaust unhooked and I told him I'm not sure of the lingo but the grey plastic box behind the engine that always has water in it. I unhooked it there so I wouldn't flood the engine with sea water while cranking. He told me to unhook it at the mixing elbow behind the manifold and almost garanteed that she'd start right up based on what I told him and 5 minutes later it was purring like a kitten. I'm an automotive / industrial maintenance mechanic but I seem to be learning more than I want to about marine.
I cleaned it out for now and will replace when we return.
Many thanks once again to Frank and you guys who answered. I'm telling all this so maybe it will help someone else in the future and so they'll know who to call when all else fails.
Dave

[Noname]

So- it was a clogged up mixing elbow?? Is that correct??

[Charlie]

Air Fuel and Exhaust.

[DotDun]

Originally Posted by dlockhart

Okay so a lot of back to basics head scratching, everything seems to be right, good spray from injectors while assembled outside the engine, compression feels ok but again I have no compression gauge here with me and although everyone I spoke to says that if you have good injector spray then it should start so you must have bad compression on 2 cylinders if it is trying to start on one. For the life of me I did nothing to cause piston or ring or ring land failure from the point of running well to not running, no ether, wd40, gas or overheat, over revving or any of that stuff so I'm not convinced of the compression theory. I called Frank at Marine Pro in Cocoa, Florida who helped me out before with engine trouble, (321-636-8950) and whom I get all my Yanmar parts from as they are an A dealer and get good pricing, and I told Frank everything I've stated here including the doubt about the compression problem. I asked him if carbon could cause anything like this as that is all that was different, the engine was making a lot of soot and black smoke due to the plugged fuel filter, he asked me where I had the exhaust unhooked and I told him I'm not sure of the lingo but the grey plastic box behind the engine that always has water in it. I unhooked it there so I wouldn't flood the engine with sea water while cranking. He told me to unhook it at the mixing elbow behind the manifold and almost garanteed that she'd start right up based on what I told him and 5 minutes later it was purring like a kitten. I'm an automotive / industrial maintenance mechanic but I seem to be learning more than I want to about marine.
I cleaned it out for now and will replace when we return.
Many thanks once again to Frank and you guys who answered. I'm telling all this so maybe it will help someone else in the future and so they'll know who to call when all else fails.
Dave

Just so I understand, you're saying the exhaust mixer elbow was plugged with soot?

[dlockhart]

Plugged solid due to a clogged up fuel filter with some sort of bio growth goop.

[ATC]

The black goo is from the micro-bio growth in the fuel tank.

The blockage in the exhaust elbow is unrelated. This blockage is the carbor caking up in the exhaust. The elbows are good for around three years. What happens is the exhaust flow is restricted, causing the fuel not to be burnt. You may have seen a rainbow sheen on the water when starting the engines and you would experience a reduction in power. Yanmar is aware of the three year change out for the elbows. What I did with my Yanmars was replace the first elbow at two years and keep the old one. Boil out the old one and replace them every two years with the reconditioned elbows.

FWIW: Regarding Bad Fuel, "if you had a half gallon of bad milk, would you add a half gallon of fresh milk to it"?

[DotDun]

I agree that the exhaust elbow being plugged is unrelated to the dirty fuel issue. In fact, I would believe that if the exhaust elbow had been clean, the engine would have kept running. Not that the fuel filters didn't need cleaned, but the odds of both stopping the engine at the exact same time would be extremely rare.

I do find the exhaust elbow problem on the 3YM20 interesting. I pulled one off my 3GM30s a while back (1700 hours) and it was wide open.

[nickc]

Originally Posted by ATC

The black goo is from the micro-bio growth in the fuel tank.

The blockage in the exhaust elbow is unrelated. This blockage is the carbor caking up in the exhaust. The elbows are good for around three years. What happens is the exhaust flow is restricted, causing the fuel not to be burnt. You may have seen a rainbow sheen on the water when starting the engines and you would experience a reduction in power. Yanmar is aware of the three year change out for the elbows. What I did with my Yanmars was replace the first elbow at two years and keep the old one. Boil out the old one and replace them every two years with the reconditioned elbows.

FWIW: Regarding Bad Fuel, "if you had a half gallon of bad milk, would you add a half gallon of fresh milk to it"?

What do you mean by "boil out" I too have had problems with the 3YM30 exhaust elbow and am on my third one. The local Yanmar mechanic advised not to try to clean them out as the wall thickness gets too thin! Personally I think the design is very poor if you have to replace them in my case after around only 200 hours.

[DeepFrz]

My theory on this is that he got some contaminated fuel through the bad filter and damaged the injectors and/or the high pressure pump. That is the reason for the carbon buildup in the exhaust elbow. Just sayin...