Diesel Smell

[Mike8074]

Hello Team,

On Tuesday I was running my boat from the boatyard back to my slip (about a two hour trip) and as I got close to home I noticed a bit of a diesel smell. I am honestly not sure if it was exhaust or fuel and as soon as I shut down it cleared a way. I was at the helm, so standing near the transom (which I get is near the muffler). I didn't really smell anything down in the cabin and there was maybe a touch of a smell in the port laz, but it was gone quickly.

What are your thoughts?

Thanks in advance.

Mike
Hull 26
www.svTwentyQuestions.com

 

[kloudie1]

Check for leaks in the diesel return line from the engine back to the tank. Check for leaking connections and check for a split/leak in the hose itself.usually, a leak in the supply line is easily visible because of the lift pump pressure, but there is almost no pressure in the return line.

 

[Hayden Watson]

The smell of raw diesel and exhaust are distinctly different and it is good to train your nose to know the difference.

Given the conditions, I am going to assume that you were smelling exhaust. When at the helm, it is not uncommon to smell exhaust even when everything is perfect with your boat. If you have a light following breeze, the wind will bring the exhaust right back into the cockpit. Given the amount of dilution this exhaust has being unconfined, this is usually not a health concern but it can sure be annoying.

 

[Mike8074]

Check for leaks in the diesel return line from the engine back to the tank. Check for leaking connections and check for a split/leak in the hose itself.usually, a leak in the supply line is easily visible because of the lift pump pressure, but there is almost no pressure in the return line.

Thanks! How would I identify that return line?

Thanks in advance

Mike

 

[Richard19068]

If the smell goes away quickly it is most likely not a diesel fuel leak. That odor would linger for hours or days or even longer.

 

[Richard19068]

How would I identify that return line?

If it a Universal diesel it would be the #2 line on this diagram, from the engine back to the fuel tank. The description says "pipe" but it is most often what you might call hose
Not to be confused with the fuel line from the tank to the engine which in the diagram first goes through items 6, 7 and 8 before going to the injection pump.

 

[Mike8074]

Mike in a yanmar. I will go research. But thank you!

 

[Richard19068]

Mike in a yanmar. I will go research. But thank you!

Same concept. Just look at the engine.

 

[kloudie1]

Yes, the high pressure line goes into the top of the individual injector and the return line comes from lower down on the injector and is usually ganged together with the other injector return lines; usually transitions from metal at the injector to a rubber fuel hose as it leaves the last injector heading to the fuel tank.

 

[Claude L.-Auger]

A few days late but you can keep the attached for future used. Don't recall if I made that pix myself or got it here on HOW, but on it you'll see what Kloudie is talking about where the rubber fuel hose return line attaches to the steel pipe after the 3rd injector

 

[Mike8074]

As an update, went down in the port laz and closed the hatch with the engine running (I had someone watching me) and i didn't really smell any exhaust. As was suggested, I felt around the couplings of the muffler for heat/leaks and there was nothing.

I am now convinced that the issue was a following breeze that blew exhaust across the transom.

I should say that sometimes I get a bit of a dark cloud of smoke when I restart the engine right after I shut it down.
I do dry sail this boat which I wonder if its a factor. Who knows.

Anyhow, not sure there really is a problem after all.

 

[dmax]

If you don't have one, now is a good time to add a CO detector.