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Old 06-05-2019, 11:33 PM   #1
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Cure for minor fuel leak

As you can see in the photo, I have a minor leak in the valve fitting going into the top of a Delrin fuel manifold. Clearly the valve is not going to turn another 360 degrees to tighten. Are there any other viable solutions? Thanks.
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Old 06-05-2019, 11:41 PM   #2
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Where exactly is the leak? It looks like one of the fittings on top of the valve may be the problem. In that case you can just tighten the fitting. You may have to disassemble it and clean the fittings first.
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Old 06-06-2019, 12:59 AM   #3
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Am I reading this right, you have two rolled up bits of absorbent pad, the one on top is dry, the one on the bottom (at the bottom of the valve body) is soaked with red diesel?

My FIRST ANSWER WAS GOING TO BE: I think your answer is disassemble, reseal. Its very likely there is a close pipe nipple between the manifold and your valve. Start with a fresh one, so the threads are worn/mashed down, and use a good sealant. I use rectorseal #5 for all fuel/oil connections where a sealant is indicated, but I'm sure there are lots more. Not sure what is on yours, reactorseal is a pale yellow color.

My SECOND ANSWER, after rereading your post - is that you need to disassemble and inspect the manifold/manifold threads. Delrin is an engineering thermoplastic, and you have metal going into it. Delrin is the trade name for DuPont acetal resins. It appears from how the fitting on the side is made that you have machined thermoplastic female pipe threads in the manifold. Brass and stainless steel have a different rate of expansion in changing temperatures, and over time will mash the threads and start to leak.

In looking at DuPont's website, the expansion co-efficient for Delrin (depending on resins) ranges from 10 x (10^ -5) to 14 x (10^ -5). Its hard to write this in TrawlerForum - read 14 times ten to the negative 5th.

http://www2.dupont.com/Plastics/en_U...ign/DELDGe.pdf

Steel thermal expansion co-efficient is 13 x (10^ -6), an order less than Delrin.

Thermal Expansion Coefficients


For comparison, polyethylene, used for most water/waste rotomolded tanks has a TCE of 18-20 x (10^ -5), almost double of Delrin. We know not to use brass fittings in those tanks because eventually leaks are almost automatic.

If you convert all the above thermal expansions into the same units (10^ -6) they look like this:

polyethylene 200
Delrin 100-140
brass 19
steel 13

This means to me as your fuel and/or engine room changes temperature from 40 F in winter up to 75 or 80 in summer and when the engine space is warm you are getting the Delrin expanding around 10 times more than the metal fittings going into it. While this is a tiny amount, its no bueno to seal fuel. Depending how much fuel is circulated and warmed by your engines, you might have that thermal cycle every time you run the boat...

My worry is either a stress crack from machining or the threads are wearing from the above. And just resealing that one might mean the others are on the way to the same condition.

IF I'm on the right track, and that's a mighty big IF, the solution might be to switch out the plastic manifold for a metal one.
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Old 06-06-2019, 06:27 AM   #4
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Compression fittings for FUEL?
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Old 06-06-2019, 08:33 AM   #5
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Originally Posted by wfleenor View Post
As you can see in the photo, I have a minor leak in the valve fitting going into the top of a Delrin fuel manifold. Clearly the valve is not going to turn another 360 degrees to tighten. Are there any other viable solutions? Thanks.
The tubing, close to where it enters the fitting, is dented and distorted. There is a strong likelihood that this is the cause of the leak. As to another responder's query apparently suggesting compression fittings for fuel being inadvisable, well, my DeFever 44 has nine of them just on the fuel manifold. Methinks this is common on many boats and since the pressures are minimal as compared to water lines using same I don't see an issue.
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Old 06-06-2019, 10:25 AM   #6
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That's just really sloppy construction between choice of material and crude workmanship (kinked tube). I would rework the system with either a manifold block of metal or tees and replay or shorten the kinked tube area.

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Old 06-06-2019, 10:28 AM   #7
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Hi wfleenor,

I feel fractalphreak is on the right track. You're assuming the manifold material is Delrin, but unless it's marked accordingly, it could be any number of non-metallic "plastics". Personally, I've never seen anything other than metallic materials (other than fuel lines) used in fuel distribution networks aboard even recreational vessels. I doubt this is ABYC-recommended practice, given plastics' low temperature tolerance.

My suggestion is to replace the manifold with one made from a suitable metallic material, verify your current valve threads (probably pipe threads) are not distorted, and seal those valves into the manifold carefully, using something like Rectorseal or Loctite PFT.

And yes, the compression fittings above the valves should be fine, as they're typically re-sealable and leak free after service.

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Old 06-06-2019, 10:50 AM   #8
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Our last boat had those plastic manifolds made by Reverso. One of ours cracked where a valve screwed into the manifold. We replaced with an identical Reverso manifold made from aluminum with new valves installed. They will build what you want to order. I would replace your manifold when you fix the leak.
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Old 06-06-2019, 11:36 AM   #9
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Our last boat had those plastic manifolds made by Reverso. One of ours cracked where a valve screwed into the manifold. We replaced with an identical Reverso manifold made from aluminum with new valves installed. They will build what you want to order. I would replace your manifold when you fix the leak.
Good call Stout.

Here is the exact configuration in aluminum with white powder coating. As Stout mentions above, the manifold should be available separately.

Note, Reverso sells manifolds for oil change systems that are made of white starboard like yours. Their diesel fuel manifolds are made of aluminum and much more suitable for fuel distribution.

Looks like even the mounting holes are the same. Should be an easy fix/upgrade.
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Old 06-06-2019, 11:39 AM   #10
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Should be an easy fix/upgrade.
Oh, now you've cursed it.

Easy? On a boat?
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Old 06-06-2019, 11:45 AM   #11
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Oh, now you've cursed it.

Easy? On a boat?
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Old 06-06-2019, 11:51 AM   #12
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Are we sure those plastic Reverso manifolds are ok for fuel? I have installed an identical one for my oil change system _ two mains and gennie (already had a pump) and it works great for that - no real pressure on the fittings.
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Old 06-06-2019, 01:56 PM   #13
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Surprised that nobody has mentioned that Teflon tape is not recommended on fuel lines.
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Old 06-06-2019, 02:59 PM   #14
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Yellow Teflon tape is ok and that’s pipe dope in any event.

Aluminum is not the best either, keep looking. Al and stainless don’t play well together, my boat is the proof.

You will probably have to change those pipes too, my preference is proper fuel hoses with crimped fittings. Most hydraulic shops can make those. Actually, similar to the blue hose in the photo, although I don’t like that angle fitting even though it’s the same as the return line on my hydraulic tank. It should have gone straight into the block or now, straight into your new manifold.
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Old 06-07-2019, 12:31 AM   #15
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Thanks LarryM, you and Stout have shown me the light. Some suggested that the stainless tubing looked less than perfect, but that is just discoloration in the photo. Some suggested that the leak was not between the fitting and the manifold, but I isolated the leak to that location. I'm not sure why anyone would question the use of JIC fittings for fuel. It does turn out that this is a Reverso manifold made for oil, not fuel and that replacing all four (return and supply in each hull) is the solution. Thanks to all.
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Old 06-07-2019, 06:14 AM   #16
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Surprised that nobody has mentioned that Teflon tape is not recommended on fuel lines.
Rector Seal #5 is a well suited sealant for diesel fuel. In a perfect world it is the choice over Teflon tape. In an imperfect (real) world tape is not uncommon.

If you redo the manifold, I'd recommend longer handle ball valves if you've the room. BTW, neat build.
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Old 06-09-2019, 11:21 PM   #17
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Thanks, Sunchaser. I do use Rector Seal #5 for nearly all fittings. I will be buying aluminum manifolds and replacing what I have. Should solve the problem.
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Old 06-10-2019, 12:14 PM   #18
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Are we sure those plastic Reverso manifolds are ok for fuel? I have installed an identical one for my oil change system _ two mains and gennie (already had a pump) and it works great for that - no real pressure on the fittings.
Valve Assembly Series

I had to download the spec sheet to find this write-up:

Manifold assembly manufactured with marinegrade
starboard (for use with oil) or powdercoated
aluminum (for use with diesel fuel).
Ideal to connect multiple hoses to one pump.
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Old 06-10-2019, 12:15 PM   #19
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I suspect it is supposed to read as:

Manifold assembly manufactured with:
marinegrade starboard (for use with oil)

or

powdercoated aluminum (for use with diesel fuel).

Ideal to connect multiple hoses to one pump.
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Old 06-10-2019, 01:26 PM   #20
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Teflon tape gives a great seal for fuel fittings IF it is applied properly. There is a technique to using it, Often it is over wrapped, or wrapped backwards or the wrong tension. A good paste sealant require work better for most people.
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