Yanmar 3GM30F light blue smoke when cruising

[skunther]

Attached is what I referred to. It appears not to be part of the fuel system, so I’m ruling it out as a source. There seems to be some leakage from the filter itself, though it is on tighter than before I changed it. When I removed the secondary filter, there was a thicker gauge o-ring packing than what was provided with the new filter, which seems odd. I assume a thicker o ring may have been used to better seal the filter housing.

Is there any reason NOT to run the engine at 3200 for 10 hours to try reset the rings? Fuel and gear oil did not leak prior to running at open throttle, and I’m wondering if it may have somehow caused the leaks? I thought the fuel filter may have been clogged and changed it for that reason (last filter change of both primary and secondary was 300 hours prior), but the leak persists.

 

[mermike]

It's probably dripping down from the bleeder screw on the high pressure pump.

 

[skunther]

I’ve found what seems to be a slight amount of diesel on the outside of #1 and possibly #2 output on the injector pump. All the other connection points are clean. Could I just tighten these nuts?
The leak started after I ran the engine hot for two 30 minute sessions (3200rpm), before I changed the secondary filter.

 

[skunther]

How much oil consumption is normal for a 3GM? I just checked my oil and after 90 hours of use the oil level is just over 1/3 up from the tip of the dip stick towards the max mark, whereas when I last changed it (90 hours ago), it was around 2/3 of the way up the dipstick toward the max mark. Is this amount of consumption during operation normal, or is it excessive?

 

[Davidasailor26]

1/3 of the dipstick in 90 hours doesn’t sound crazy to me. @Kings Gambit posted a little while back that he spoke to a Yanmar tech and got an indication that if oil consumption is less than about 0.5% of fuel consumption it’s within tolerance. I’d also pay attention to whether the consumption is about the same as it’s always been or suddenly worsening.

 

[Alan Gomes]

I’d also pay attention to whether the consumption is about the same as it’s always been or suddenly worsening.

Actually, it would not be unusual for it to get worse with age. The Yanmar GM Workshop Manual says somewhere (and I'm going by memory here) that some oil consumption is normal, and that it will be the highest when the engine is brand new and first breaking in, and then increase once the engine achieves a high number of hours. It will be lowest in the middle portion of its life. (I could probably track down the quote if I took the time, but that's an accurate rough paraphrase.)

You're probably right that it shouldn't "suddenly" worsen, i.e., go crazy over night. But it will be worse for an older engine, at least per Yanmar themselves.

 

[skunther]

1/3 of the dipstick in 90 hours doesn’t sound crazy to me. @Kings Gambit posted a little while back that he spoke to a Yanmar tech and got an indication that if oil consumption is less than about 0.5% of fuel consumption it’s within tolerance. I’d also pay attention to whether the consumption is about the same as it’s always been or suddenly worsening.

Doing the math, 0.5% of 1/2 gallon/hour fuel consumption over 90 hours = 0.9 quarts. Seems pretty spot on. I’d figure 1/3 of the dipstick is less than a quart.

 

[RoyS]

It may not apply here, but when you change your oil and filter your filter is empty until you run the engine. Checking the oil after first running the engine usually shows a change due to the filter filling with oil. In any case, your oil consumption is not excessive.

 

[skunther]

The oil consumption I have confirmed to be ~1 quart, which works out to be 0.5% of fuel consumption. For reference, if anyone has the same engine, 1 quart of oil brought the level up the dipstick approximately 1/2 of the length from the very tip (not the low level mark) toward the high level mark.

 

[skunther]

Reviving this thread regarding fuel in the engine compartment. After changing the primary filter and cleaning up the engine as well as I could, there appears to be no more fuel leaking as of the past 15 hours of use. No signs of drops anywhere. It remains puzzling, as there were no leaks prior to running the engine at 3200 in an attempt to “re-seat” the piston rings and eliminate smoke in the exhaust. I’m not sure at this point if I should make another attempt to re-seat them by running at high rpms for 10 hours, or if that might cause the leaky fuel issue again.
I did notice when bleeding the injector lines that I could not seem to get fuel to come out of one of the lines (I believe it was #3, but I would have to confirm). The other 2 bled fine, and the engine ran fine when started up. I checked the compression valves on each cylinder, and each one affected the engine, indicating they were all getting fuel. I thought nothing further of it at the time.
Could it be that that line was clogged somehow, which was causing leaking downstream of the injector pump? If so, it seems that may have been the cause of the leak.