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Old 03-31-2019, 08:16 PM   #21
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So, maybe your pickup tube fell out of the fitting?


These are $20 on Amazon...
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Old 04-05-2019, 08:31 AM   #22
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[QUOTE=Riverguy;753234]re: "Bungs are there, at bottom and just a few inches from the front. Looks like they were welded in the tank but never connected."

Ok...that's what I guessed. So...your boat was originally plumbed for twins, but (probably) the factory effed up. Either that or an idiot previous owner removed the crossover hose, maybe because it developed a leak and he needed to slip it past a surveyor.

Now...a single diesel engine with twin saddle tanks simply MUST have the two tanks connected! Your diesel engine draws fuel from both tanks but returns unused fuel to only one tank.

This is why you must have a crossover hose.

There is no reliable way to cause a single engine to draw evenly from two discreet (un-connected) tanks, nor any way to ensure the returning fuel coming back from the engine is distributed evenly between the tanks.

So...I think we now know your problem.

The first thing you need to do is cross connect your tanks, using the bungs you identified, and with shut-off valves (per ABYC) If you send me a private message, I will send you a photo of what it should look like.

The good news here is that it is very unlikely that your problem is pinholes in your pickup tube(s). The bad news is that whatever idiot (previous owner?) did this....probably did a lot of other stupid stuff to your boat.





So here is the latest chapter, not resolved yet but I think the problem has been identifed.
First picture is of the crossover bung which has never been connected. To control flow, the tanks each have valves for supply and return. In normal configuration you can withdraw from a tank and return to same tank, or return to the other tank (not recommended) if you need some balancing. Nice feature to keep the tanks isolated if you want to or need to for any reason.

Now for the problem; I called the manufacturer of the tank, Florida Marine Tank of North Carolina. They were very helpful and actually pulled up the drawings of the tanks. After 22 years they still have the drawings on file! They told me that the pickup tube is welded to the bottom of the threaded bung before it goes in the tank and then the PU/bung assembly gets welded on to the top of the tank. See picture from their website. That is why I could not move it or remove it. They said that the weld or the fitting to the bung may have developed a pin hole and allowing air to be pulled into the line. This makes sense since when I close the tank valves the air bubbles go away. If it was leaking anywhere else it would draw more air into the system because of the higher vacume.

Now for the really good news; They make a replacement (nylon ?) pick up tube that fits inside the current welded tube. The new tube has a 90 degree aluminum fitting on top along with a anti-siphon valve all for $60 bucks. Only problem I see is because it is a semi-rigid tube I may need to cut an access hole in the floor above the fitting to get it in the hole. Not a problem as a sofa sits over the potential access hole.

New tube should be here today and hopefully I will be able install it over the weekend. If it works, I will replace the other tank assembly also.

Thanks for everyone’s suggestions and help. Will post a final follow up after everything is installed and working (fingers crossed).
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Old 04-05-2019, 08:40 AM   #23
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And whether you need a crossover is debatable.



In some cases necessary or desireable...some cases not needed. My boat and many I have run does/did it have one.
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Old 04-05-2019, 11:26 AM   #24
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This thread reminds me of one on my “pet peeves” from my days in industrial maintenance. Electricians were the worst, and since no electricity is involved in this thread I’ll stick with them to minimize offending all the contributors of good ideas in this thread.
Something quits working, and the electrician is called. He does his troubleshooting and decrees that “it is wired completely wrong, no wonder it doesn’t work”. Boss tearing hair out “it has worked for 20 years this way, something changed that made it stop working. Go find what changed”.
I fall into the trap all the time. Fixing things most often requires finding what changed, and I go off critiquing and looking for improvements in the whole system. The latter is a worthwhile endeavor, but if the goal is to restore yesterday’s operating condition, it sometimes delays me finding “what changed”, and getting going again.
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Old 04-05-2019, 11:32 AM   #25
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And whether you need a crossover is debatable.



In some cases necessary or desireable...some cases not needed. My boat and many I have run does/did it have one.


Don’t forget that if both feed valves are open, and there is no air in the piping the top feed lines from both tanks are in fact a “crossover”, and will equalize the tanks as a siphon just as surely as a bottom connected crossover. You do in fact have a “crossover”, with the advantage that instead of draining both tanks into the bilge everything will stop if something in the crossover piping breaks.
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Old 04-05-2019, 12:27 PM   #26
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You make a good point. I thought of putting a hose in a container and see what happens. Putting it thru the empty fitting hole will be easy, then just the fitting with no valve.

You also mention sealant? I read somewhere that the pickup tube may be welded to the fitting. The integrity of the seal depends on how tight you tighten the fitting which presses on the welded tube. Is sealant used to help seal the tube to fitting?
Sealant was for any threads on the fittings. No way to seal the tube ( inside the tank) to the fitting but everywhere else there are threads should have sealant.

The idea with the hose is to reduce the number of connections (and possible leaks) to a minimum.


Interesting that the mfg. makes a replacement part... Just wondering if the problem has showed up B-4... Hnmmmmm.
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Old 04-05-2019, 01:00 PM   #27
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Don’t forget that if both feed valves are open, and there is no air in the piping the top feed lines from both tanks are in fact a “crossover”, and will equalize the tanks as a siphon just as surely as a bottom connected crossover. You do in fact have a “crossover”, with the advantage that instead of draining both tanks into the bilge everything will stop if something in the crossover piping breaks.
Even with both feeds open, my tanks don't equalize as in a true crossover. They may a little sometimes, but I don't expect them too.
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Old 04-05-2019, 01:01 PM   #28
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re: [I]

Now...a single diesel engine with twin saddle tanks simply MUST have the two tanks connected! Your diesel engine draws fuel from both tanks but returns unused fuel to only one tank.

This is why you must have a crossover hose.

There is no reliable way to cause a single engine to draw evenly from two discreet (un-connected) tanks, nor any way to ensure the returning fuel coming back from the engine is distributed evenly between the tanks.
I'm afraid this is incorrect. I have built boats with twin saddle tanks, single engine, no cross over. After the boat is built the supply and return valves are adjusted until tanks are drawn from and returned to evenly, after which the handles are removed and wire tied adjacent to the valve. It can be made to work properly.

A balancing line definitely makes life easier, but some believe that a balancing hose, plumbed to the bottom of tanks, is a liability, as a leak means a very big spill. There is no ABYC prohibition against balancing lines or fittings on the bottoms of fuel tanks. Because it's readily available in this diameter, the hose used for these lines is typically A2, which is technically rated for fuel fills, unlike A1 it is not rated for continuous immersion in fuel.

As a test, as others have suggested, I'd drop a clean hose into the tank as the test pick up. I have seem metallic and Nylon pick up tube break and fall into he tank.
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Old 04-05-2019, 01:11 PM   #29
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@Djoub,
Glad to see that you are tracking down your fuel feed issue. One thing I do notice, the red plugs in the bungs for the crossover connection look suspect to me. I would consider either replacing them with threaded aluminum bung plugs or install the shut off valves and crossover hose. The hollow red plastic plugs currently installed look like the temporary plugs that are in place when the new tanks are shipped from the manufacturer. If that is the case, I would be replacing them sooner than later, thanks,
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Old 04-05-2019, 02:36 PM   #30
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A single diesel engine boat with twin saddle tanks MUST have the tanks cross-connected. Think it through and it'll become apparent.
I too am going to disagree on this. I have a single diesel with saddle tanks, and valves for both supply and return. No dedicated cross connection. I always return to the same tank as I draw from, and manage athwartship trim by drawing from the appropriate tank, switching back and forth to draw them down somewhat evenly. Usually I switch every couple of days. I also have water tanks P&S, and so if one is full and the other empty I can maintain trim by running one fuel tank at a higher level to offset the imbalance. This system has worked well for me.

If the fuel return goes to only one tank then a cross connection is needed, but that seems to me to be a short cut solution.
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Old 04-05-2019, 02:37 PM   #31
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Really? Naah...you're pulling our legs.

Quote:
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I have built boats with twin saddle tanks, single engine, no cross over. After the boat is built the supply and return valves are adjusted until tanks are drawn from and returned to evenly, after which the handles are removed and wire tied adjacent to the valve. It can be made to work properly....
Re: "I have built boats with twin saddle tanks, single engine, no cross over. After the boat is built the supply and return valves are adjusted until tanks are drawn from and returned to evenly, after which the handles are removed and wire tied adjacent to the valve. It can be made to work properly."

No, it can't. But you're kidding right? I hope you are because I want to laugh here and say "O.K. Steve, you had me going..."

This would be a total kludge, and (if you think about what you just said) it is readily apparent that this kludge can only work if the tanks somehow, miraculously remain at the exact same fill level over the years, and the engine is always run at it's max fuel flow rate. Never going to happen.

1) In this design, where does the generator draw from/return to? Do you propose the same kludge for that?

2) In this design, when you need to shut off the fuel valves (functional fuel shutoff valves ARE required by ABYC) -- how do you do that when you have "removed the handles and wire tied them".?

3) Re: "the supply and return valves are adjusted until tanks are drawn from and returned to evenly". Really? Using what measurement tool or method? Using "flow restriction" to balance fuel draw, you'd need to adjust them while pulling the maximum gph draw from the engine, but then, when running slowly at let's say, 1/10th the gph of maximum draw, the whole system would become useless and revert to a simple gravity feed. The restriction presented by any orfice varies exponentially with flow rate. At lower flow rates your valve restrictions will do nothing.

4) On the return side, you are seriously going to place restriction valves in the fuel return lines and adjust them to "balance the flow" among the tanks? What fuel flow rate do you use for this? You do know that (once again) whatever restriction you choose will only work for the specific flow rate you've chosen, right? And of course, if you mess that up (even a little) you are going to destroy an injector pump and/or blow up the return fuel lines and spray fuel all over the bilge. Check with any diesel engine manufacturer on that, and I am pretty sure ABYC won't let you do that either. Incredibly dangerous.

Good one Steve...you had me going.
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Old 04-05-2019, 02:53 PM   #32
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Wow...

[QUOTE=Djoub;754504]
Quote:
Originally Posted by Riverguy View Post
re: "Bungs are there, at bottom and just a few inches from the front. Looks like they were welded in the tank but never connected."
Quote:
Originally Posted by Riverguy View Post

So here is the latest chapter, not resolved yet but I think the problem has been identifed.
First picture is of the crossover bung which has never been connected.

That red cap stuffed into the bottom of your tank where the crossover hose was -- looks like plastic. NO WAY that was done by a professional.



Someone has REALLY kludged up this boat.


At this point, I am guessing someone tried to "fix" the leaky fuel pickup tube by "retiring" the entire tank, and in the process they removed the crossover hose and crammed a plastic cap into the hole(s).


Unbelievable...but good job getting (almost) to the bottom of it.
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Old 04-05-2019, 03:07 PM   #33
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Don’t forget that if both feed valves are open, and there is no air in the piping the top feed lines from both tanks are in fact a “crossover”, and will equalize the tanks as a siphon just as surely as a bottom connected crossover....

Good point...I stand corrected. That said, what do you think of this?


That red plastic plug is at the very bottom, foreward corner of the tank.



I (for one) would not put fuel in that tank.
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Old 04-05-2019, 03:19 PM   #34
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I too am going to disagree on this. I have a single diesel with saddle tanks, and valves for both supply and return. No dedicated cross connection. I always return to the same tank as I draw from, and manage athwartship trim by drawing from the appropriate tank, switching back and forth to draw them down somewhat evenly. Usually I switch every couple of days. I also have water tanks P&S, and so if one is full and the other empty I can maintain trim by running one fuel tank at a higher level to offset the imbalance. This system has worked well for me.

If the fuel return goes to only one tank then a cross connection is needed, but that seems to me to be a short cut solution.

Yes...so rethinking this I am wondering why the MS350/390's made the crossover hose standard on the singles?


The siphon action of the cross-connected pickup tubes could keep tank levels balanced (albeit slowly), but is the generator a factor? Could it have been a safety thing for the inevitable times when owners forgot what position they'd left the fuel valves in? Or, is it just so owners don't (necessarily) have to fill from both sides and then wait a few days for tanlk to balance out via the pockup tube hoses?
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Old 04-05-2019, 03:27 PM   #35
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This thread reminds me of one on my “pet peeves” from my days in industrial maintenance. Electricians were the worst, and since no electricity is involved in this thread I’ll stick with them to minimize offending all the contributors of good ideas in this thread.
Something quits working, and the electrician is called. He does his troubleshooting and decrees that “it is wired completely wrong, no wonder it doesn’t work”. Boss tearing hair out “it has worked for 20 years this way, something changed that made it stop working. Go find what changed”.
I fall into the trap all the time. Fixing things most often requires finding what changed, and I go off critiquing and looking for improvements in the whole system. The latter is a worthwhile endeavor, but if the goal is to restore yesterday’s operating condition, it sometimes delays me finding “what changed”, and getting going again.

Hey...I might resemble that remark! ;-)



As owner of a MS390, I know that crossover is supposed to be there in the first place, and now seeing that red plastic cap stuffed into the hole where it used to be is a danger sign. I agree that discovering how it was built in the first place, and then finding out what's been changed usually is the quickest way to find the problem.
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Old 04-05-2019, 03:39 PM   #36
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Yes...so rethinking this I am wondering why the MS350/390's made the crossover hose standard on the singles?
My assumption has always been that it was cheaper to plumb a single return and crossover than to have switchable returns. Maybe too they wanted to keep things simple for owners.
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Old 04-05-2019, 05:04 PM   #37
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HI, On the old Celestial, (now destroyed by Hurricane Michael), I ended up replacing all of the valves as a result of installing a fuel polisher. The problem was that I used garden variety valves, I found that most valves are rated for pressure only, not for vacuum. I finally had a long conversation with the Conbraco valve technicians. They confirmed that their Apollo valves were rated for both pressure and vacuum (at the time, their catalogs did not state the ratings). I replaced all of the valves in the entire system with Conbraco's Apollo valves and the problem of air infiltration almost stopped. I also found that the Racor 1000's have a tendency to leak (vacuum) in several places, which I tracked down one by one and eliminated. In the end, the fuel system was very tight, i.e., no fuel leaks under any circumstances.
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Old 04-05-2019, 07:20 PM   #38
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Crossovers are not needed in many cases.

You can run on and return to one tank at a time.

Plenty of boats set up this way.

The only boats II have run (that I recalll) with crossovers were so you could fuel just one side. Had nothing to do with the engine (s).
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Old 04-05-2019, 09:17 PM   #39
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Crossovers are not needed in many cases.

You can run on and return to one tank at a time.

Plenty of boats set up this way.

The only boats II have run (that I recalll) with crossovers were so you could fuel just one side. Had nothing to do with the engine (s).


And I simply do not see the rationale for ever drawing and returning to two tanks at the same time.
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Old 04-05-2019, 09:20 PM   #40
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Good point...I stand corrected. That said, what do you think of this?


That red plastic plug is at the very bottom, foreward corner of the tank.



I (for one) would not put fuel in that tank.


Well, I didn’t think about it until you asked, because it does not seem to be leaking. Now that you ask, here’s my guess. We know that we have a very thoughtful tank builder, based on their ability to supply drawings of a tank made 20 years ago, and having a ready to ship dip tube to fix a weakness in the original design. My guess is that as a convenience to the future owner they welded on a weldolet to ease the future addition of a drain plug, or bottom discharge without having to weld on a tank in place, or with fuel residue, but they did not drill the hole in the tank plating. That red plastic piece is not even threaded, it is simply a dust plug to keep the female threads clean as we wait for someone to need or want to drill the hole.
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