36 LRC diesel leak mystery

[chicagocat]

Here's a bit of a mystery.

I got on the boat yesterday after being off for a couple weeks. I smelled some diesel, so I looked around and found that the port side bilge had about 2 gallons of diesel in it. I hadn't checked it over the last month or so, so I'm not sure exactly when it accumulated. I cleaned everything up and did a couple experiments.

I figured that the leak was from the port side engine, but after running each engine by itself, I found that the diesel begins to appear in the port bilge when I'm running the starboard engine ( the starboard bilge is dry).

The engine compartment on the starboard side has some water in it, but I can't smell much diesel. Plus, I can't figure out how it would get over to the port side.

I'm going to spend more time looking into it tomorrow, but in the meantime, I thought I'd see if anyone here had any ideas.

Thanks,
Brendan

[SecondWind]

The Port and Starboard engines both have separate pickup and return lines, where the unburned excess fuel is returned to the tank, under some slight pressure (can pressurize the fuel tank). Normally the tank is vented, and the pressure is relieved, but if the vent is clogged you may force fuel under greater pressure through one of the fuel lines. The port line picks up at a slightly lower level than the starboard. If all of the fuel lines are tight, there should be no problem with a leak, but if there is a slight leak it could account for this problem. Check that the vent hose is elevated continually and does not droop down onto the fuel tank. Use support blocks if necessary. (Also make sure that your return line is not siphoning).

I have noted the following: The low pressure fuel pump screws often need to be tightened and seep sometimes; the copper gasket on the fuel filter bleed will leak a lot if not replaced occasionally; the o-ring on the fuel filter also needs frequent replacement; and on rare occasion the reinforced line to the high pressure pump can rupture (metal braid covered hose).

Hope this helps!

[chicagocat]

Thanks Terry,
It sounds like you're on to something here...

I'm not on the boat right now, so I can't quite picture it all. Where does the fuel tank vent?

Thanks,
Brendan

[SecondWind]

Brendan,

Mine vents on the forward top of the tank. The hose goes through the Starboard locker and out the stern. I have an overflow device on mine. I found that it was drooping on the fuel tank and filled with fuel which stopped the venting action.

[chicagocat]

Ah...interesting. So maybe a couple wood blocks with 3M adhesive to prop up the hose?

Of course, I have to find out the source of the leak first.

This is all very helpful. Thanks again.

[Bob]

terry, this was a timely thread as I noticed a frayed cover on one of my HP fuel lines and was being lazy about dealing with it. With a trip down the ICW coming up I guess I'll fix it now.

[Tex Hill]

Brendan,
Where was your fuel leak? I have a similar problem now. My leak "seems " to be from the high pressure line fitting out of the injector pump. Kind of hard to tell untill I can spend some time watching.

Thanks, Tex
S/V Footloose

[chicagocat]

Hi Tex,

We put the boat on the hard in November and it's been such bad weather here that we really haven't been able to look at it. Since obviously, fuel only leaks when the engine is running, we're going to wait a couple more months before we dig in and try to pinpoint the problem.

So, in short, there's no solution yet. I'll post more when we find the problem.

Brendan

[chicagocat]

OK. I am still getting some diesel in my port bilge. I looked very carefully today and here's what I've found (keep in mind that the order of my boat systems knowledge is : sailing, electronics, plumbing, pretty much everything else, ....diesels).

The fuel line that I think is the return is tie-strapped to the manual bilge hose in the engine compartment. It runs to the front of the engine, then seems to disappear forward under the teak and holly floor boards with the bilge pump hose. There is a fitting ( I think, I can't see) where it runs under the floor. That fitting seems to be cracked, and the leak seems to be coming from near there. I have no idea why this fuel hose seems to leave the engine compartment and go forward. I don't know if it's possible to lift the floor in the port rear cabin without removing the hanging closet, etc.

Does this make any sense at all?

Brendan

[SecondWind]

Brendan,

This does not make any sense at all. I replaced all of my fuel lines, and both the feed lines from the tank and the return lines run through the lockers in the stern of the boat. I too had diesel in the bilge and traced it to two sources, both in the fuel filter (the one attached to the engine). The first problem was the o-ring that seals the filter to the top piece. The second was the copper gasket in the bleed screw on the filter. I have also found that from time to time the screws on the feed pump need to be secured. In addition the high pressure lines can deteriorate and should be replaced (I have spares, since mine are beginning to look bad) Merle and Jan Larson on Prairie Dream have replaced theirs. It has a braided metal cover and sits high on the front of the engine.

I can't conceive of any reason the fuel line would go forward, unless there was a change in the pickup location in the tank. Lift your cockpit floorboard and see where the fuel lines feed in and trace them from there.

James or anyone an LRC, Comments?

[chicagocat]

Terry,

I was about to post an update when I saw your post. Further inspection makes me think that this is the propane line running through the engine room and toward the stove. Sorry....told you this wasn't my area of expertise.

The propane line is sitting where the fuel seems to pool, at the area in front of the engine. That's what had me confused.

I now think that my problem is the same one you had, with the filter which attaches to the engine. That filter sits almost directly above where the fuel seems to pool. Now if I can only get it fixed before I leave on Tuesday for a 5 day cruise...

Thanks as always...

[maxicrom]

From the amaunt of diesel you are describing inthe bilge it sounds like you should be able to see at least a drip - the return lines will only have a flow when the engine is running. If there is an inline fuel issue your engine will be very hard to start, possibly requiring bleeding before it will start. As a test I would visually inspect the entire run of the fuel system for wet lines, if the filter you are describing is a spin-on type the gasket may be loose or swelled or a fitting is loose. Normally fitting on filters mounted to the boat don't loosen up the way items on the engine do from vibration. If there is no visible sign of leakage you may to do the visual test again with the motor started - if it doesn't start or runs very rough for few minutes that may be a sign that the problem is somewhere before the injector pump - fuel line from tank --> primary fuel filter --> line to engine lift pump --> lift pump (side of the engine) of fittings --> secondary filter or fittings --> fitting, lines to injection pump. My primary filter is in the cokpit locker and would be difficult to leak into the bilge - if was leaking it should be damp as diesel takes forever to dry.

Hope this is helpful., good luck.

Over the last few years we sometimes noticed a diesel smell from the engine compartment - and the secondary fuel filter bleed screw and the fuel pump would sometimes weep or be damp. Luckily the worst was a tiny bit of weeping. Tightening everything - banjo fittings, fuel pump diaphram screw, etc... would minimize it and wrapping a rag (or oil diaper) in that area would keep it from getting in the bilge - it would eventually get worse and need to be addressed again. Finally tired of this I ordered a new fuel pump and all the copper washers and went through the whole system from the fuel line connection to the injector pump. It's better now but I still notice a little dampness around the bleeder screw area. Is this a Yanmar trait? I would like to resolve all leakage and get rid of that diesel smell. This is my first Yanmar and I know that over tightening can be just as bad as loose fittings.

Thanks, any input form Yanmar pros would be appreciated

Maxi

[DanRankin]

If I may make a comment, the later LRC models had an inspection hatch cut into the Teak and Holly sole in the port aft cabin, the hatch was made of the piece that was cut out and trimmed in Teak, thus making it easy for inspection of that aft bilge.
I have had a look at a couple of 36's with the LRC and the outboards, both having the same fuel tanks, but different delivery systems. The leak I feel is coming from chaffed lines through bulkheads or from the motor itself. The last one I saw with this problem was ANNE Z.....and it had me baffled.....and I built the boat! I would love to get my hands on a 36LRC and track this down for good! The Yanmar motors do vibrate a great deal and even on the MV34's we had fuel alarms going off during commissioning and the cure was to tighten or loosen the sensor....so a loose connection on the motor is a probability......Dan