Kohler 8E0ZD Fuel Leak

The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.


Jun 11, 2018
Vessel Name
Indigo Star
Vessel Make
2006 Mainship 400
We are traveling north on our 2006 Mainship 400 and while at anchor last night here in Beaufort NC, I was running our Kohler 8E0ZD genset for an hour or so and I noticed a slight diesel fuel smell. We were downwind of a fuel dock so at first I thought it was somebody fueling but being late that didn't really add up. I opened the rear deck hatch where our generator access is and opened the front sound shield door and with a flashlight I saw a small amount of diesel fuel in the mount base pan area. Not good.....

Upon further investigation, while the unit was running, I could see a small amount of fuel seeping out from what is the intake manifold?
I had wiped it clear right before the picture but the yellow circle is where the fuel was seen. (See pic)

I'm not 100% sure but I don't think diesel fuel should be in the intake manifold so my guess it was coming from somewhere else, perhaps above it and had worked its way there? Unfortunately this genset installation is not one that allows access or visibility to the upper side where the 3 injectors are so unless a larger access panel is cut I really don't know how else to locate the leak?

Since it seems to be a small leak could that maybe be a low pressure return line that might be leaking?

I am also pretty sure this is a 2005 Yanmar 3TN74 diesel.

Any suggestions or similar experiences would be appreciated.

Indigo Star


  • 20240427_180843.jpg
    75.2 KB · Views: 70
  • 20240427_164310 (1).jpg
    20240427_164310 (1).jpg
    105 KB · Views: 67
  • 20240427_172615.jpg
    127 KB · Views: 68
  • 20240427_171212.jpg
    154.7 KB · Views: 74
Maybe spraying out of one of the hp fuel line fittings on the injector pump? Watch it closely with the generator running. I’d also look at the banjo fitting on the pump and the rubber supply line that runs right above the area you circled. If it’s a high pressure leak it should be pretty easy to see.

Would be easier to trace without that worthless sound shield.
I'm with Doug... and would be looking at the the hose, fitting and lines/connections to the Injectors.
Mirrors, paper towels sometimes help finding hidden leaks. Boroscope either self contained or phone/tablet accys are cheap these days. Harbor Frt & Amazon have choices.
Yes, I agree, however as everyone knows, access is the big problem here, you can't even see anything. The previous owner cut two small deck plates that do not add much access. I am thinking the first step is to install a much bigger rectangular flush mount access hatch?...I know that sounds crazy but even if I find it with a boroscope then I gotta repair it.


  • SmartSelect_20240428-081819_Chrome.jpg
    30.6 KB · Views: 22
Jeff, get rid of the sound shield. Seriously, it does almost nothing except restrict access. Don’t cut a big hole in your deck.

Pay someone to do it if you have to, it will be worth it. I promise.
I totally agree, I really do not want to cut a hole in the deck, but even if the entire shield is removed I don't think you really improve access to the fuel injectors and fuel lines on the "very top" of the engine do you?
My best guess is that's where the problem is?
I totally agree, I really do not want to cut a hole in the deck, but even if the entire shield is removed I don't think you really improve access to the fuel injectors and fuel lines on the "very top" of the engine do you?
My best guess is that's where the problem is?
It still won't be great, but it will help some, would open up a few inches on the top.

That said, I would verify that it is not something other than the injectors before you go to the trouble. An injector, or injector line, would most likely cause an obvious leak, more than just a slow seep. Seeping leaks, in my experience, are more likely on the low pressure side of the fuel system.

Start her up with all of the sound shield covers off, then use a flashlight and watch everything carefully.
Update - Leak was found today, unfortunately I had to create an access panel to the injector area to locate and repair the small fuel leak. I can see a small amount of fuel coming from the top of a nut on the middle injector. Tried to tighten it more but it was already really snug and no room to get a wrench in there much. I suspect the seals or washers are in need of replacement. I tried to get some pics to share. I guess I should replace all three seals and gaskets and washers at the same time?


  • 20240430_195447.jpg
    101.9 KB · Views: 52
  • 20240501_150557.jpg
    123.8 KB · Views: 48
  • 20240501_150813.jpg
    122.5 KB · Views: 44
  • 20240501_150608.jpg
    115.9 KB · Views: 47
Well, at least you don’t have to worry about that sound shield anymore, lol. Glad you found the leak. I think there is a copper crush washer in there, but I am not sure. Let us know what you do.
Top Bottom