Fuel Pipe ID

[jaysweet]

I noticed that one of the metal pipes (presumably a diesel "fuel oil" pipe) which runs under the heat exchanger on my Yanmar 2GM20F is looking really rusty/flakey. Pretty sure it's from a slow saltwater leak in the past or present.The question is: what part is this? Despite looking at many parts diagrams, I'm really not sure. It's on the starboard side of the engine. Here's the place where the pipe starts:

and here's the rusty spot:

I think it might be number 7 on the following webpage,

Yanmar 2GM20 Parts Catalog with Pictures (PDF) - J/30 Class

Yanmar 2GM20 Parts Catalog with Pictures (PDF) - J/30 Read more about bolt, gasket, yanmar, assy, washer and cooling.

www.yumpu.com

(sorry: see fig. 37 in that manual)
helpfully captioned as "pipe", but I'll be darned if I can tell for sure. If it is, then it's on the low pressure side of the system, which makes me worry less in the short run. In the long run, I think it needs to be replaced. Any help would be welcome.

 

[dLj]

It's got a banjo fitting on it. It also says in that manual that it is a fuel line. I'd get a wire brush in there if I could and clean it up. I'd also want to hit it with a rust inhibitor. If it's hard to get in there, I'd probably shoot T9 into there are a minimum - or pick you preferred product...

dj

 

[Ralph Johnstone]

More than just a bit of a coincidence here. I spent the last winter working in this area when I replaced all of the rubber hoses within the engine compartment. This is one configuration that is a little less than crystal clear. I have been meaning to contact @SycloneDriver and grill him for an explanation of what this is and now is just as good a time as any. This is what I have on my 2GM20F :

The bajo fitting just downstream from your rust spot doesn't seem to do much more than just lower the path of the fuel as it heads back to join the cooling return fuel from the injectors and from there to the fuel tank.

Moving right along here, your rusty line is coming from a banjo fitting which has split the fuel path from the secondary filter. Some of that fuel is going to the high pressure pump and the rest is return fuel going back to the fuel tank. Thoroughly confused ? Welcome to the club. I can understand WHY the fuel is following this path but I don't see the need for the second banjo fitting in the path. Maybe it's helpful in the manufacture of the engine. Not for us mortals to know. Here's the exploded dwg. from the Yanmar parts manual :

It's missing more parts than it includes but use your imagination and you'll see something in there.

Here's the tail end of that bypassed fuel coming from the secondary filter as it heads back to the fuel tank :

The short story here is that your rusty line is at ambient pressure and a light cleaning should take care of the problem unless it's in really bad shape and you think it may leak and make a mess. Also try to eliminate the source of corrosion if you can.

 

[jaysweet]

It's got a banjo fitting on it. It also says in that manual that it is a fuel line. I'd get a wire brush in there if I could and clean it up. I'd also want to hit it with a rust inhibitor. If it's hard to get in there, I'd probably shoot T9 into there are a minimum - or pick you preferred product...

dj

The question is whether or not I feel comfortable just cleaning it up instead of replacing it. If it's not on the high pressure side (as I suspect), this seems like a more viable idea. (It's definitely hard to get in there, so this is a project either way.)

 

[jaysweet]

More than just a bit of a coincidence here. I spent the last winter working in this area when I replaced all of the rubber hoses within the engine compartment. This is one configuration that is a little less than crystal clear. I have been meaning to contact @SycloneDriver and grill him for an explanation of what this is and now is just as good a time as any.

The bajo fitting just downstream from your rust spot doesn't seem to do much more than just lower the path of the fuel as it heads back to join the cooling return fuel from the injectors and from there to the fuel tank.

Moving right along here, your rusty line is coming from a banjo fitting which has split the fuel path from the secondary filter. Some of that fuel is going to the high pressure pump and the rest is return fuel going back to the fuel tank. Thoroughly confused ? Welcome to the club. I can understand WHY the fuel is following this path but I don't see the need for the second banjo fitting in the path. Maybe it's helpful in the manufacture of the engine. Not for us mortals to know. Here's the exploded dwg. from the Yanmar parts manual :

It's missing more parts than it includes but use your imagination and you'll see something in there.

Here's the tail end of that bypassed fuel coming from the secondary filter as it heads back to the fuel tank :

The short story here is that your rusty line is at ambient pressure and a light cleaning should take care of the problem unless it's in really bad shape and you think it may leak and make a mess. Also try to eliminate the source of corrosion if you can.

Ralph: thanks for your very thorough response. Even if you (and I) still have some questions about why they designed it this way, I think you've clarified in my mind that the part I'm looking at is indeed #7 in fig. 37, which is part number 128296-59550. Given that it seems to cost IVO $155, and this is a low pressure pipe, I'll probably be just cleaning it up and painting it. It seems pretty obvious to me that there's a slow leak of sea water, almost certainly from the heat exchanger just above the pipe. But it's very slow - probably just a drip every now and then - so it'll be pretty hard to detect and to know when I've got it fixed. Most of my engine still looks pristine, but there's a small area of rust and flaked off paint, sort of near this leak. If anyone has any ideas on how to clean up and re-paint that area without extreme effort / removing half the parts on the block, I'd be glad to hear it.

My engine access is actually pretty good: full access to the front, a panel on either side, full access to the back (ish), but there's no way I could have taken the picture you did, as there's some large chunk of boat bulkhead in the way. I'm thinking the heat exchanger needs some attention: I can see that you've replaced the large hose (with the red cap on the hose clamp), since mine is painted silver, like most of the hoses on the engine.

Thanks especially for the pdf of the parts manual. The thing I was linking to wasn't searchable, and in fact looked like someone took pictures. I've saved it off for posterity. Anyway, I may be slow to respond for a couple of days, b/c we're off for a couple of days on the boat! First trip of the year.

Thanks again!

 

[Ralph Johnstone]

Given that it seems to cost IVO $155, and this is a low pressure pipe,

Holy jumpin' crap. Pass the defribrillator !

Yeah, it's a complicated little piece but I'd look far and wide before replacing it. Hopefully, it's not as deep corrosion as it looks. Remember, iron corrosion products expand by a factor of about 10X so keep your fingers crossed. Use steel wool rather than emery to avoid removing any more metal than you have to.

I can see that you've replaced the large hose (with the red cap on the hose clamp), since mine is painted silver, like most of the hoses on the engine.

That was replaced during the Great Hose Renewal of 2023 when all fuel, antifreeze, and sea water hoses were renewed.

If anyone has any ideas on how to clean up and re-paint that area without extreme effort / removing half the parts on the block, I'd be glad to hear it.

It is believed those instructions are hidden within the Covenant of the Ark and will be revealed when that artifact is found. Until then, it's small pieces of emery on a stick and whatever else you can find. I went through the same thing when the vacuum breaker on the starboard side of the engine started to leak and pi$$ed sea water down the side of the block. Did a few calculations and found I could live without it due to the water line at that location.

 

[Ralph Johnstone]

Pulled a screen shot from a slowly panned 4K video I'd shot of every point on the engine :

This shows the lowest point in the mixing elbow which could cause problems if it were ever exceeded by the water level :

 

[dLj]

The question is whether or not I feel comfortable just cleaning it up instead of replacing it. If it's not on the high pressure side (as I suspect), this seems like a more viable idea. (It's definitely hard to get in there, so this is a project either way.)

Small little stainless steel wire brush might get in there. You might want to try Ospho to stabilize it. It's hard to tell from the photo how much pitting and such is present. a low pressure return line doesn't need a lot of wall thickness to remain viable...

dj

 

[ggrizzard]

A Dremel tool might get in that tight space.
Or, a modified drill bit with sand paper tip.