Odd fuel leak: Need a diagnostic clue

[matts997]

After returning from a 20 mile cruise, I discovered a pretty severe fuel leak beneath my fairly new, re-manufactured Yanmar 2GM20F (with 62 hrs). Fuel was pooled beneath the engine and aft under the dripless seal. Images attached.

No obvious source of the leak yet, but tomorrow I plan to go over the fuel line, etc. to hopefully get at least a start on diagnosis.

I have a question for you all about a possible clue: I first detected a faint fuel odor ~ 1 mile from my slip, but dismissed it as a Navy boatyard smell, as the engine was running perfectly--as it did all the way to our slip. Any ideas about where in the fuel line/engine there could be a leak this bad w/out affecting the engine's performance at all? Thanks

 

[kloudie1]

That far aft, I’d really suspect the fuel return line from the injectors to the tank.

 

[Ralph Johnstone]

WOW ! ! ! ! That's one big leak.

You've "GOT" to be able to see the fuel leaking from the engine when it's running. Anything ?

 

[ggrizzard]

On the fuel return line or at one of other five fuel line connections.
Some re-installers are sloppy.

 

[matts997]

Thanks, this gives me a place to start. Makes sense it would be a fuel line connection point, especially in a recently re-installed engine. A stupid question, but is it a total of 5 connections on the 2GM or 10 (5 x 2 end points)?

I didn't restart the engine after we docked, as I was concerned about so much fuel around a hot engine. But tomorrow, I'm going to start it up and run it for a couple minutes to see what I can see.

The re-installers are reputable, a Yanmar dealer, and they’ve promised to fix it...but they can't get to it for a week or two and I'm hoping to get lucky and find something I can fix myself.

 

[Rich Stidger]

I feel your pain. I have a similar problem with a different engine and have been unable to locate the leak. Perhaps some of the great suggestions made to me in my thread will help you. See: Volvo MD22L-B fuel dripping from air intake
A couple questions to answer: You have 62 hours on this rebuild and re-install. Is this a new problem that you didn't see in during the first 60 hours?
Can you feel fuel wetness on any fuel connection, or anywhere along a fuel line? Has anything changed, like the level of fuel in the tank?
Your first picture is clear that a fuel pool is in the engine compartment pan under the drippless shaft gland. But the second picture is not clear where it was taken- can you post another picture showing more engine that will make it clear?

 

[matts997]

Thanks for the link. Answers to your questions below:

You have 62 hours on this rebuild and re-install. Is this a new problem that you didn't see in during the first 60 hours?
Yes, completely new. It happened within the last 10 miles I put on the engine yesterday...I suspect during the last mile of the trip. Something must have suddenly loosened or burst open. Though nothing I saw was obviously the culprit.

Can you feel fuel wetness on any fuel connection, or anywhere along a fuel line? Has anything changed, like the level of fuel in the tank?
Haven’t’ had a chance yet to do that--going back tomorrow to check everything and if necessary, start the cold engine for a couple minutes while observing. Like RJ said, it has to be pretty obvious with that much leaked fuel.

Just yesterday I noticed the amount of fuel in the tank seemed excessive for the distance motored.

Your first picture is clear that a fuel pool is in the engine compartment pan under the drippless shaft gland. But the second picture is not clear where it was taken- can you post another picture showing more engine that will make it clear?
I don’t have another image now, but the one you’re referring to is looking straight down on the starboard oil dip stick...the red right below that is fuel pooled beneath the engine.

 

[Ralph Johnstone]

But the second picture is not clear where it was taken- can you post another picture showing more engine that will make it clear?

This may help with the alignment :

There is no lift pump on my engine shown above.

 

[Rich Stidger]

<snip>
Haven’t’ had a chance yet to do that--going back tomorrow to check everything and if necessary, start the cold engine for a couple minutes while observing. Like RJ said, it has to be pretty obvious with that much leaked fuel.
Well, take a look at my post #18 in my thread. That is a lot of fuel, maybe 2-3 ounces total and I still can't find the leak.

Just yesterday I noticed the amount of fuel in the tank seemed excessive for the distance motored.
Explain your statement above. Do you mean that you expected to see less fuel in the tank? I don't know how you would judge the fuel level accurately- gauges are notoriously inaccurate.

I imagine that your leak will be fairly easy to find. New engine, lots of connections disturbed, and a relatively large amount of fuel leaked. Lots of possibilities and they should all be relatively easy to test. That is unless you have a black cloud like I have.
Let us know what you find. Maybe your find will help me and others.

 

[Ralph Johnstone]

I'm not sure how many fuel connections there on the 2GM20F but it seemed like a load of them when I replaced every last section of fuel line within the engine housing which is really a discarded Nike shoe box:

The hoses were coming on to 24 years and the sections within the housing were a little harder than their continuing sections (supply and return) outside of the engine housing so time for a renewal of everything inside the box. This additionally included all AF and sea water hoses. It was the original job from hell.

The below shot shows five fuel connections and that's without even getting into the lift pump, #1 and #2 fuel filters, and the return line connections. Many, many, connections from which your leak could be coming.

The fuel return line connections required the removal of the air filter and still were near impossible to connect and clamp :

The bad hose connection on the left of the "T" was only picked up by the camera and then re-done. Didn't have my borescope along for this one. All the work in this area was done by feel due to the nearness of the port side bulkhead. I still go into fits of cursing and swearing when I think about it.

 

[matts997]

So glad I saw these images before heading out to the boat this morning---extremely helpful!! I often wish I were more knowledgeable about boat mechanics, etc. so I could contribute as much to this forum as I get out of it.

I’ll let you guys know the outcome.

Thanks for the help.

Matt

 

[matts997]

"Explain your statement above. Do you mean that you expected to see less fuel in the tank? I don't know how you would judge the fuel level accurately- gauges are notoriously inaccurate."

My statement was poorly written, I should have said: "the amount of fuel USED--according to the fuel gauge--seemed excessive for the distance motored.” We were coming back from a marina we often visit and that distance usually consumes a bit less than 1/8 of the tank. This time the gauge showed almost a 1/4 tank of fuel consumed.

 

[Ralph Johnstone]

I wouldn't worry about how much fuel went where at this stage, only where the hell is it coming from ?

When you're down there, could you take a look in the compartment directly under the engine and see if there is a limber hole ?

 

[Ralph Johnstone]

One last thought @matts997 . Be sure to take many pics from many angles of the offending leak when you first find it. You may have further problems if you have a significant amount of fuel trapped within your boat's ribs and stringers.

 

[matts997]

I ran the engine for a minute and observed a fine but soaking mist that seemed to be coming from one of the connections on the port side of the fuel strainer (secondary, engine-mounted filter). It didn’t appear to be coming from the strainer itself, but I can't be certain as the fuel was spraying everywhere. To get a better look, I’ll have to remove the engine cover and use a tarp or something to prevent fuel from spraying into the cabin.

Could this be as simple as a dirty fuel filter, so clogged that it’s forcing leaks through adjacent connections? As far as I can tell, there’s no sludge in the primary filter.

Ralph--there’s no hole on the engine side of the limber hole. I think the leak is spraying so much fuel on the engine and inside the engine cover, fuel on hoses, etc. could be draining into the area beneath the dripless seal.

 

[Ralph Johnstone]

I think the leak is spraying so much fuel on the engine and inside the engine cover, fuel on hoses, etc. could be draining into the area beneath the dripless seal.

Unfortunately, I think that's exactly what's happened to deposit fuel in the compartment under the dripless seal.

Is this the location of the source of the leak you are seeing :

If I'm correct (and only if correct) and have drawn the spray correctly, what you are seeing is not coming from the secondary filter. This is the discharge pressure coming from the lift pump according to the Yanmar service manual :

It's hard to read, but the pump discharge pressure is 0.1 kgf/cm² or in numbers you can get your head around, 1.422 PSI. That's just a soft puff of wind and will not discharge fuel in a spray but rather a dribble.

A more likely source would be the injector pump below the filter at a discharge pressure of 2418 PSI :

Looking at the location of the two steel tubes carrying high pressure fuel to the two injectors, this may be a better guess as to where your leak is coming from.

CAUTION: don't get your fingers anywhere near the fuel leak as 2400 PSI will very neatly cut your fingers off.

Ralph--there’s no hole on the engine side of the limber hole.

Good news. Clean up the fuel and plug the hole so no fuel gets in there. If it does manage to get in there, you'll smell diesel fuel until the end of time.

The re-installers are reputable, a Yanmar dealer, and they’ve promised to fix it...but they can't get to it for a week or two and I'm hoping to get lucky and find something I can fix myself.

Good luck if the repair consists of simply tightening a fitting. At the very least, I would get the installers back in to clean your engine and its compartment as it will stink for quite some time and the odour may permanently stick to fabrics. And, I imagine you paid a pretty sum for the work done.

Keep it coming along with any pictures you can get.

 

[matts997]

Very thorough explanation and clearly marked images. Yes, the mist/spray is coming from the general vicinity you’ve indicated on the images..and the source could very well be the injector pump, as the spray is coming out with impressive force.

At this point, I'm going to leave this to the installers--I want to keep all my fingers! Hopefully it'll become clear who is responsible, the re-installers or the shop that sold me the remanufactured engine.

I’ll keep you posted, thanks again.

 

[WayneH]

CAUTION: don't get your fingers anywhere near the fuel leak as 2400 PSI will very neatly cut your fingers off.

When I was working at the refinery, we would search for 1250# steam leaks with a broom handle. You can not see superheated steam even on muggy days but when the end of the broom handle DISAPPEARED you knew you had found the leak. Hopefully, detection methods has improved since I retired.

 

[Ward H]

@Ralph Johnstone Very impressive posts with photos & markings!

 

[matts997]

Ha! Disappearing broom handle-- that’s an image that will stay with me for awhile!