Diesel Fuel Leaks at connectors

[Barnaclebem1]

I own a 30 year old Nor-Star, Anastasia 32 Cutter sailboat with a Volvo-Penta 2cyl aux. diesel. I am having drip leaks at a couple of junctions. At the T- split directly off the tanks... at that T I have small irritating leaks. Also... on the diesel bulkhead mounted heater I get the same small drip leak. I've heard that diesel is actually more viscous that H2O... therefore even if a connection is water proof... diesel may leak at the same type of application.... To make a long story short I need advice, ideas, recommendations regarding the connections. I know... the boat has been out of the water for multiple years and now its in the water and I'm running around trying to catch up on all the work presented just from not being used. I am preparing for passage making. Please advise.
Thank you
BD

[rugosa]

Sounds like a fitting issue rather than an engine or heater issue. At 30 years old you likely need to dismantle connections, remake connnections and maybe replace them. If tank is aluminum use aluminum fittings (stainless tank = stainless fittings, similar metals wherever possible) to match to avoid negative action, presuming it goes on to fuel hoses. Same idea at heater. Should be able to source at a tank manufaturer rather than marine supplier to avoid marine mark up. Also check quality of materials as they are not all the same.

[hellosailor]

BD, diesel is less viscous than water. It is thinner than water, not thicker.

If the connections were welded or soldered, they may have pinholes in them from age and corrosion. Or the leaks may come from old rubber hoses fit to them: You don't say what the connections are.

Either way the answer is clean or replace or reinstall fittings. A patch applied over them is not likely to be a permanent solution.

[Rockter]

Really, if the crush washers are in good condition, the union between the banjos and the planar surfaces should seal. Do not make the mistake of over-tightening them, as the thread is often very fine, and it may strip.
I have never tried it, but if the surfaces are dry, you might try dusting them with some talcum powder, then watching carefully where the leaks are.

For may years I have run a pressurised fuel system, at about 3 psi. If it leaks, I see the wee drops forming, but I cannot draw air and that is the main issue.

There is an added fire risk with a pressurised system, but the stsrting reliability is improved.

Rockter.

[hellosailor]

"Really, if the crush washers are in good condition, "
Often they can be (and are) re-used, but really, the entire point of a crush washer is that it deforms during normal installation, to mate two pieces of metal that are not machined to a perfect tolerance.
So unless you are very lucky, and the two pieces of metal were perfectly machined, parallel and smooth, the crush washer does deform on installation. If it is thick enough and the deformation is small, you can crush it again and still have it fill the gap. But it is very much like a high-pressure version of plumbers putty or window glazing putty: Once it squeezes out, it doesn't flow back, it really should be replaced.
Unless your engine loves you more than most of the duplicitous beasts do. They usually just like to wait for the least convenient moment, and THEN that crush washer starts sucking in air. You know what happens next.

[RichH]

You probably have 'compression fitting' on these leaking connections. Boat builders uses these compression fittings because they are cheap and easy to install. However, compression fittings are 'one time close-up' only fittings ... as after the first 'tightening' the copper tube becomes 'deformed' and you really cant properly 're-tighten' after the tube becomes initially 'compressed'. Sequential 'tightening' of compression fittings only further 'compresses' the tube and risks 'cracking' of the closure nut. To make these fitting stop leaking you will either have to 'trim' or cut away the area of the tube that has been 'compressed' by the previous 'compression ferrule' installation OR really should choose to replace the entire section with 'double flared' connections. Double flaring is easy to do if you have the proper tools.

BTW ... copper is reactive with diesel fuel, so if this is a 'serious' fuel delivery system, you really should consider to replace the entire system and replace with double flared stainless steel tube and double flare connections - expensive but 'bomb proof' ..... also allows you to operate a PRESSURE feed fuel system (lift pump AT/ON the tank) which is vastly superior to a 'vacuum motive' fuel delivery system.

[erps]

BTW ... copper is reactive with diesel fuel,

what are the results?

[RichH]

results ... copper sulfate in the lift pump valve faces and injector closure surfaces and a constant 'thinning' of the copper walls.

[jameswilson29]

Who sells the stainless steel tubing and double flare connections?

[SlowButSteady]

Originally Posted by hellosailor

BD, diesel is less viscous than water. It is thinner than water, not thicker....

Nope.

At 40˚C, water has a kinematic viscosity of about 0.7 cSt (centistokes), while for diesel #2 the value is anywhere between 2 and 4 cSt (depending on the formulation of the diesel). And, yes, higher values mean thicker in this case.