Diesel leak

[robbieg]

Have a leak on my Yanmar 3GM30F at the banjo connecting the fuel pipe from the lift pump to the injector pump. Have replaced the copper washers a couple of times & this seems to sort it for a short time & then the leak returns. The faces of the couplings seem ok. Any suggestions what I try next? Is it time for some gasket sealer stuff?

Thanks.

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[Jools_of_Top_Cat]

No

No

No

please do not use instant gasket or anything similar on fuel pipes.

Find out why the leak keeps returning, have you tried a fine wet and dry abrasive on the pipe ends, it is probably corrosion. If it is warped then you may have to replace. But do not fix the symptom. This is fuel, you need to TRUST your fuel installation.

If you do use instant gasket, please never moor near me nor raft on me.

<hr width=100% size=1>Julian

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[toad]

Heat the new copper washers over the gas ring until they are cherry red then quench them in a bowl of water. This softens the copper and allows it to make a good seal.

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[Talbot]

is it possible that the coupling is 10mm and the pipe 3/8"? The difference (0.5mm) is enough to enable a seal initially, but then to leak over time. Most copper fuel pipe sold in this country is 3/8".

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[andyball]

maybe worth checking that the banjo bolt isn't too long & bottoming out before a good seal can be made.

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[brianhumber]

The copper washers MUST be annealed before use, ie new or done your self using a blow lamp.

Then the nut must be tight, remember this joint will suffer vibration. If the pipe starts to move before the nut is fully tightened and you stop tightening to avoid bending the copper pipe, thens its odds on the washers will start leaking. In this case you must support/hold the copper pipe as you tighten the nut fully down. Use a ring spanner not a shifter.

I would never use joint material on these types of joint and used to bannish any of my engineers I found adopting such cowboy tricks to a months bilge strum cleaning after watches.

It is not unknown for the braze/silver solder to develop a hairline crack between coupling and pipe. Use some wet and dry to polish up the pipe and banjo surfaces to see any diesel coming through cracks.

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[charles_reed]

I had exactly the same recurrent problem on the tank-pump connection on my 2GM.

Finally cured the problem (caused by engine movement gradually unscrewing the banjo), by fitting a keeper close to the pump so that all the movement is confined to the flexible piping.

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[robbieg]

Charles sorry to be a bit dim but exactly how does a keeper work. A bit more detail would be appreciated since I suspect the problem is the banjo undoes over time with engine vibration and so hopefully your solution will work for me.



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[AndrewB]

Err .... why?

>>If you do use instant gasket, please never moor near me nor raft on me. <<

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[Moose]

"It is not unknown for the braze/silver solder to develop a hairline crack between coupling and pipe"

I know!!! I and I also know that 17litres or engine oil can get through said crack in about 2 minutes!

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[Jools_of_Top_Cat]

Re: Err .... why?

because I do not want someone who will willingly allow a fine spray of fuel or even a drip around their engine room by employing such a cowboy repair to their system.

A little harsh I know, but the concept just scared me. I know the original poster did not, in fact was obviously concerned about this approach, enough to ask advise on here. I apologise for my over enthusiastic approach to the answer, was late and too much wine.

BTW, I did not know about annealing the copper washers before replacement, I have learnt something today, makes total sense. I would have blindly replaced the pipes. Thanks for that peeps.

<hr width=100% size=1>Julian

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[AndrewB]

Re: Err .... why?

OK, I confess, I have in the past used instant gasket on washers in the fuel line, as a bodge until a proper fix can be arranged.

But I'd have though you would have appreciated that, Jools, as its proved totally effective for a while. Otherwise there would have been, as you say, a fine spray of fuel or even a drip around the engine.

I thought the the main reason for avoiding gasket goo wasn't that its ineffective, rather that it might get into the fuel line, pump or injectors causing a blockage, and so a sudden loss of power.

FWIW, the one time I had persistent trouble with a banjo it was in fact caused by a partial blockage further along the line (no, not caused by gasket goo), which was creating back pressure. It's probably worth just checking this.

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[Spyro]

I'll probably get shot down in flames for this suggestion but I used it on a persistent leak on a banjo fitting on the electric fuel pump over a year ago and it has been ok since. FIBRE WASHERS.
I'll wait for the responses

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[brianhumber]

Re: Diesel leak - Fibre Washers

You can remain aloft or can go to the bar for a G&T at the end of your watch (see my earlier post!) .
Properly consistuted fibre or other man made material can be used as long as the material is not affected by the fluid being transfered in the pipes.
The key is selecting the right material for the application ;
e.g. rubber insertion for seawater
klinger 100 for oils,water, saturated steam
klinger 1000 ( reinforced with stainless wire mesh) for superheated
simply metal to metal for high pressure

This was 'drummed' into me by my first Scottish Chief who was not at all impressed when I, as a first trip cadet, offered up a gasket made from diaphram rubber instead of rubber insertion. I got to know the layout of the bilge piping system very quickly as a result.

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[catmandoo]

Check the Banjo bolt . Is there sufficient landing on the bolt to centre the washers . I had a similar problem and found that the problem was not the washers but the bolt landing which when inserted did not protrude enough through the banjo to centre the washer . A new bolt inserted did the trick

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