Yanmar 3GM30F - periodic misfire and white smoke

[elmerfudd]

I was laid up from surgery, so hadn't taken the boat out for over 6 months until this weekend.

After running fine for about 45 minutes, the engine began mis-firing, emitted a large cloud of white smoke, then ran fine. Oil pressure was OK, water temp a bit hotter than normal, around 180F at 3000-3100 rpm. I checked the engine compartment for leaks and such, found nothing. There was less than a 1/8" of gunk on the bottom of the secondary fuel filter, which I drained off.

It repeated again on the way back.

Back at the dock, I checked things out after the engine cooled. Here's what I found:

- The oil had been overfilled past the hi level mark on the dipstick. My bad I didn't check it before departure, figuring it was OK because it had just been filled by someone I trusted. I normally do my own oil and filter changes, but since I was laid up I had the local marine tech do it.


- The compartment under the hot water heater was full of fresh water (not coolant), and was steamy warm. The water had leaked from the overflow valve, presumably from overheating by the engine coolant fluid. The heat exchanger hoses from the engine were hot to the touch.

- The engine coolant level was fine. No obvious coolant or oil leaks in the engine bilge.

- The oil doesn't look milky, at least what I saw on the dipstick.



Any thoughts? What else can I check?

[DeepFrz]

Are you sure the oil was overfilled and that you are not leaking diesel fuel into the oil sump? One sign of a leaky low pressure fuel pump failure or a high pressure seal failure is elevated amount of lub. oil in the engine sump.

Your white smoke symptoms could mean water in the fuel or un-burned fuel going out the exhaust. If steam then it is sign of overheating.

[roverhi]

DeepFrz pretty much covered it. Drain the excess liquid out of the sump and take the boat out again or run it at the dock in gear at cruise rpm for at least a 1/2 hour. If the hiccup shut it down and check the oil again. If it's high again would start with the lift pump and then a compression check.

[Captsteve53]

WHITE SMOKE occurs when raw diesel comes through the exhaust completely intact and un-burned. Some causes of this include:
1)Faulty or damaged injectors
2)Incorrect injection timing (could be a worn timing gear or damaged crankshaft key way).
3)Low cylinder compression (eg: caused by leaking or broken valves, piston ring sticking, cylinder and/or ring wear, or cylinder glaze)

When white smoke occurs at cold start, and then disappears as the engine warms up, the most common causes are fouling deposits around piston rings and/or cylinder glazing. Use of our Flushing Oil Concentrate and FTC DE- carbonizer address these respective problems.

Water entering combustion spaces will also create white smoke. Faulty head gaskets and cracked cylinder heads or blocks are a common cause of water entry, and are often to blame. Unfortunately, expensive mechanical repair is the only proper solution here.

So in your case water in the fuel/condensation from sitting or as previously mentioned leaking fuel into your oil which would raise your oil level from the following places:
1) Fuel lift pump diaphragm/seals
2) Injector tips corroded/leaking
3) Injector pump issues -seals

Cheers Steve

[Greg Mason]

You had mentioned that the oil was overfilled. I have seen a case where the oil was forced up past the rings and burned off through the exhaust. But, if you are gaining oil level, or gaining coolant levels, likely a different issue is at hand.

[topmast]

As the fuel leaks into the oil sump, usually the first sign, failing checking the dipstick will be a total runaway as the engine sucks up the excess. This probably destroys the engine and may stick a piece of connecting rod through the hull. All this drama has happened before so consider yourself lucky.

[Steve Bean]

Would a laboratory analysis of the lubricating oil be a good idea, to quantify diesel fuel in the crankcase? This also would provide other information about engine condition.

[boeing1]

did you smell the oil on the dip stick for signs of diesel

[bil56]

A simple test:
Blotting paper, drop a little oil, if dark spot in the center = oil AND light stain on the outside = diesel, oil-diesel mixed, probably by the diesel pump

[Symphony]

thanks for the in-field test ideas