black smoke in engine room at start up

[ken matejka]

An odd sequence of events occurred earlier today involving my 2gm20f that I hope one of the diesel gurus could clarify for me. I arrived at my boat today, a day following 2 days of strong north wind(25-40kts), to perform my ritual weekly crank of my trusty yanmar. I start the motor, let her warm up, engage the propeller in forward and bring her up to operating rpm while in the slip if I am not going to go sailing---it is far too cold for sailing this weekend. I have done this for the past 3 years that I have owned the boat. I follow all maintenance recommendations--usually doing things ahead of time. This motor has never, and I mean never, given me any trouble---it has rarely if ever not cranked on the first push of the starter button. Anyway, I arrived at the boat today, opened the thruhull, turned ignition on, and hit the starter button. Starter worked, but motor did not turn over after 1-2 seconds--odd for my motor. I went back downstairs and opened the engine compartment to "look at things". Everything seemed to be in order, there was no water in the engine room bilge. Racor had no water in it. So, I went back topside and tried to crank again. Motor tried to fireup after about 5 seconds of cranking but shook violently and then stopped. Went back downstairs and open engine compartment again and found an enormous amount of thick black smoke!! What!! After the proverbial smoke cleared(with help of an onboard fan) I also noted that now about 1/2 inch of water was present in the engine bilge. My first instinct was the mixer elbow, so I reached around to feel it. It was dry, however I did feel a bit of rust back there(I can't see back there in my boat). This was very alarming to me so I checked all hoses etc for leaking and found nothing--once again everything appeared to be in order. I went back topside and tried to crank again and after a bit of trying(1-2minutes intermittently) she reluctantly started---and ran well. No funny sounds, vibrations, smoke, water---like nothing at all had just happened??? I then ran her the normal 20 mins at 2500 in the slip without any hiccups, killed the motor, and restarted without any difficulty. Any ideas on what in the world all of this was? Do you think that maybe the strong north wind and waves somehow overfilled my exhaust?? But, my exhaust hose comes to the top of the lazarrette after exiting the muffler before exiting out the stern hole--a solid 3 feet. I would think that much rise would almost make it impossible to flood the muffler. However, the north wind does drive waves into my rear starboard quarter from across the turning basin in the marina. Any thoughts on this would be helpful as I certainly never want it to happen again. thank you very much, ken matejka

 

[RonD]

Interesting

I'm not a diesel "guru" but a few things come to mind.1. Did you leave the ignition switch on for 20-30 seconds prior to pushing the start button the first time? This allows the glow plugs to get up to temperature & preheat the fuel-air mix. That might allow for the hard starting.2. It sounds as if you have an anti-siphon loop in the exhaust line. If that's the case, it would be highly unlikely that the wind would be able to backfill the water-lift muffler. I haven't a clue as to the water in the bilge observation.3. The excess shaking and ragged running suggests you weren't firing on all cylinders at first. Could have been a temporary fuel blockage to an injector, or a bad glo-plug, or both.3. The black smoke suggests blow-back through the oil breather.Was the temperature excessively cold? Might account for the hard-start, particularly if you had a bad glo-plug.--Ron

 

[Kevin]

???

Hello Ken,My guess is that when you tried to run engine the cylinders had a over abundance of fuel and a s result when it fired it created a massive amount of carbon that found its way into the engine compartment through some oil breather. The water in the bilge is a strange one. In the cranking of the motor could the fresh water pump filled the riser (?) and because the engine exhaust was not present to push fumes and water out it drained into the bilge? If the water was coming up the anti siphon when you where sailing in heavy winds I would have thought that you would have found water back in the engine. (in the crank case oil) It would have made its way through an open valve. Wish I could help more. Kevin

 

[Andy]

Backfire in motion

My speculation is that the enjoy was just about to fire off when you gave up. The compression explosion of the fuel spent the engine backwards so all the black smoke that typically goes out the exhaust went out the breather (hence the black smoke). As for the water???? I guess if it was running backwards the water would flow back out the breather too-cough cough balooy. I have seen an engine with a clogged anti-siphon loop that had water up to the breather. Miracuously (sp?), the water was drained, cylinders fogged, refogged and lubed and she fired off and runs today (its alive!)