Mystery Yanmar 2GM20F Fuel Leak

[Steve E.]

Good morning all,

I have a mystery leak on my 1999 Hunter 310, with a Yanmar 2GM20F motor. With the engine off (and assuming while running) I get several drips a second of what I believe is diesel fuel. I have not been able to track down its source, drips into the bilge pan under the engine. This all started towards the end of the season last year, and only started after a overheat of the engine.

Last year, I had my impeller go out, and ended up overheating the engine to the point we heard the engine temp alarm. Shut it down, got towed in, and ordered a new replacement impeller. Replaced the impeller a few weeks later and everything appeared to be OK. Fast forward to the end of the season and my wife complained of smelling fumes in the aft cabin. Opened up the engine compartment only to find about an inch of fuel collected in the pan.

Had a buddy who is "diesel certified" (in trucks) and thought it was a head gasket. He thought the overheat caused some damage to the block, and recommended trying a head gasket sealant instead of replacing the head gasket right away. Ran down to the auto parts store, bought some head gasket sealant to put into the radiator, and began running the engine as described on the directions. 20 minutes into it, the temperature alarm sounds, and apparently my thermostat got stuck closed and was preventing fresh water into the engine. <sigh>.

I replaced the thermostat this past weekend but I am still seeing a drip or two a second of fuel after all of this.

I am lost. I dont know what to look for next. I have tightened the fuel filter screws, though I have not replaced anything fuel related at this point. I just don't know what I should be looking for. Since I cant trace the drip (because it drips from the lowest point of the engine, at least the best that I can tell) I don't want to just go replacing anything/everything fuel related. To compound issues even more, I am an hour away from the boat in landlocked Colorado with zero on the water support, and no trailer or ability to pull the boat if I needed to.

So I thought I would turn to the collective brain for suggestions. At this point (and I knew it would come eventually) boat ownership is beginning to suck. :cry:

Thanks in advance to for help.

 

[Ken Cross]

Ours had a leaking fuel pump. Look for a wetted looking gasket.
Ken

 

[Steve Dion]

I would check and/or replace all of the copper crush washers on the high pressure side of the fuel system. The manual fuel pump is also a good place to check.

You can dust suspect areas with baby powder to check for leaks too.

Another thought, could it be anti-freeze?

 

[woodster]

check your fuel return line at the end of the injector run back to the tank and all your fuel lines going to the injectors

 

[Famos_Amos]

Check all the fittings along the fuel lines between the components. They have a way of loosening over time, causing leaks that flow down and drip elsewhere.

 

[mz4wheeler]

A good mechanic WILL find the source of the leak. Which side is leaking, left/right/front/back?

In my case, I had oil dripping from my front gear housing assembly, lower left. Apparently this is a common leak on these engines.

My point is, you need to completely take off the front cover, run the engine, get your head in there with a bright shop light and a large mirror. That is a big leak and it should be obvious where it is coming from. It's there somewhere.

Weird how your buddy associated a possible fuel leak with a head gasket. Was there white smoke billowing out of the exhaust? If there was then I'd suspect a head gasket. But that would only be associated with a water leak. Now you have to flush that gunk out of your cooling system.

Check your oil level. Thoroughly clean and dry the dip stick and check again. Eliminate the possibility of the fuel pump leaking into your crankcase.

Fuel pump, fuel strainer, fuel injection pump, injector pipes, injectors, fuel return pipe, each square inch needs to inspected.

Most likely is the fuel pump diaphragm, as stated earlier.

 

[Ralph Johnstone]

With the engine off (and assuming while running) I get several drips a second of what I believe is diesel fuel.

That's not a leak you've got but a geyser .

In addition to all previous posts above, try taping (duct tape) and jamming wads of paper towel around parts of the engine. This may give a better idea of the source. Once you have a soaked wad of paper, throw a match to it to make sure it burns. If it doesn't burn, it's not fuel, and it's back to the drawing board :cry:.

 

[kloudie1]

If you are sure it is diesel, it is NOT a head gasket. If there is a head gasket problem,that is not what is causing the diesel leak. I also would suspect the "banjo" copper crush washers on each side of the fuel "lift" pump. Check hoses for cracks and drools .. in addition, carefully cross tighten the screws holding the top of the fuel pump onto the lower body.. The paper towel search will be helpful in locating..

 

[Claude L.-Auger]

With the engine off (and assuming while running) I get several drips a second of what I believe is diesel fuel. I have not been able to track down its source, drips into the bilge pan under the engine.

Several drips a second with the engine off is not a drip it's a gusher. Do not assume, check it while running. If you get several drip a second with engine off, you should get much more while running. Remove front panel, get a flashlight and ask someone to get that engine started and bring the RPM up. You should find it in no time. A bunch of good ideas here but I'd suggest to smell the wad of paper rather than setting fire to it ! If you indeed want to go for the fire test, bring the wad out and somewhere safe on land ! If indeed it is antifreeze, your coolant level should be lower. Get a pressure tester and check it.

 

[smokey73]

Assuming you buy your diesel from a marine location like a marina or marine fueling location it will have red dye to indicate it has not been subject to road tax. You don't need to set it on fire or even smell it (but smelling it is okay) to tell if it is diesel fuel. On a clean white paper towel it will be distinctly reddish in color.

 

[Steve E.]

Wow....all great advice. I will take a closer look asap.
I am 99.9% sure it is diesel. Smells like diesel, feels like diesel. Didnt light it on fire. I might try that with a small dab of it on a paper towel.

I wish my marina had diesel. Kind of. I have to manually cart it in from a local gas station. The only thing they sell is super expensive premium unleaded for the stink pots. Like I said, land locked Colorado.

Thanks again for all the good advice. I will definitely take all suggestions under consideration.

 

[PGIJon]

I quickly located a fuel leek by shoving blue Kleenex in every nook and carney in the engine. Even the slightest leak is very noticeable on the Kleenex. Good Luck!

-Jon

 

[Allan12210]

You can also collect a little in a glass vial and add some water. Shake and look for a second phase. That wkill tell you its diesel.

 

[Benny17441]

A small fuel leak, has nothing to do with overheating. The buzzer alarm is designed to go off well before the engine reaches critical temperature. If you shut the engine down soon after the alarm went off there should be no consequences. I don't like the word "never" but in this case I will say never put those sealers in a radiator as all they cause are clogs. If your engine is not getting air in the fuel lines causing hard starting then the leak is small or only evident when the engine is running. In this case check the fuel pump as the likely culprit. If the pump is dry then check the banjo connectors and the return lines.

 

[texasprinter]

Fuel Leak

Good morning all,

I have a mystery leak on my 1999 Hunter 310, with a Yanmar 2GM20F motor. With the engine off (and assuming while running) I get several drips a second of what I believe is diesel fuel. I have not been able to track down its source, drips into the bilge pan under the engine. This all started towards the end of the season last year, and only started after a overheat of the engine.

Last year, I had my impeller go out, and ended up overheating the engine to the point we heard the engine temp alarm. Shut it down, got towed in, and ordered a new replacement impeller. Replaced the impeller a few weeks later and everything appeared to be OK. Fast forward to the end of the season and my wife complained of smelling fumes in the aft cabin. Opened up the engine compartment only to find about an inch of fuel collected in the pan.

Had a buddy who is "diesel certified" (in trucks) and thought it was a head gasket. He thought the overheat caused some damage to the block, and recommended trying a head gasket sealant instead of replacing the head gasket right away. Ran down to the auto parts store, bought some head gasket sealant to put into the radiator, and began running the engine as described on the directions. 20 minutes into it, the temperature alarm sounds, and apparently my thermostat got stuck closed and was preventing fresh water into the engine. <sigh>.

I replaced the thermostat this past weekend but I am still seeing a drip or two a second of fuel after all of this.

I am lost. I dont know what to look for next. I have tightened the fuel filter screws, though I have not replaced anything fuel related at this point. I just don't know what I should be looking for. Since I cant trace the drip (because it drips from the lowest point of the engine, at least the best that I can tell) I don't want to just go replacing anything/everything fuel related. To compound issues even more, I am an hour away from the boat in landlocked Colorado with zero on the water support, and no trailer or ability to pull the boat if I needed to.

So I thought I would turn to the collective brain for suggestions. At this point (and I knew it would come eventually) boat ownership is beginning to suck. :cry:

Thanks in advance to for help.

I had a similar issue on my Oday 28. Your gaskets have broken their seal due to overheating. Try replacing the gaskets on fuel pump and tighten hose and fuel line connections they all expand when heated. Good luck!

 

[Steve E.]

All,

I just wanted to say thanks to everyone that offered suggestions. I was successfully able to track down the leak and repair it this weekend. For those interested, it was located at the fuel pump. I replaced both brass washers, trimmed the overheated fuel line, and reattached everything tight. Knock on wood, that appears to have resolved the issue.

Thanks again to the community and I am glad it was a cheap, easy fix.

 

[PGIJon]

Just curious Steve... How did you eventually track it down?

 

[Steve E.]

Just curious Steve... How did you eventually track it down?

I actually used your recommendation, kind of. I looked all over for colored Kleenex, and none of the stores I was at carried any. Apparently colored Kleenex is no longer "in". So instead I used marine toilet paper, stuffed it all around the engine area and tracked it down by finding the one bunch that was wet. After that it took contorting myself armed with a strong flashlight that found the leak.

I did learn though that the leak was not all the time like I originally thought. I discovered that it also occurred when the engine was running, but I didn't notice it until the engine was off and I looked under the block to see the collection of drips. I don't like to stick my head that close to moving belts with the engine running. Based on that, I assumed it was dripping while off.

What I discovered, and it makes total sense now, is the fuel line was pressurized some and continued to bleed its pressure out once the engine stopped running, which is why I thought it occurred when off.

Thanks for all the great suggestions and help.

 

[PGIJon]

Thanks for the update. I read about the Kleenex in an earlier thread and used it earlier this year. It pin pointed the leak immediately. Glad to have passed it on! We found the Kleenex at Sam's Club. Enjoy this years sailing! -Jon