[C320-list] Leaky fuel tank?

[Guy Smith]

Hey Marek!
I feel your confusion.I had a similar problem last season with Pleiades, a '97 #452. The evidence of a leak was traced to the same area that you saw pooling. I pulled the tank over the winter and had it inspected and pressure checked with the sending unit still in it. All was good with the tank. Since the pooling was under the tank, the only other culprits could be the fill and vent lines which are smooth connection fittings or the fuel lines, which are barbed. Since it was winter and I didn't pay attention to how secure the rubber lines were attached when I took them off (it was cold!), I assumed that it was some connection to the tank or faulty hoses. I do remember over filling the tank to where the fuel bubbled out of the vent during a fill, so I may have had fuel in the rubber fill and vent hoses for a time until the fuel level decreased. It may have seeped out then. I inspected the hoses and did not find a smoking gun, replaced some and put it all back together. I'll keep an eye on it now, but I do still wonder what it was. Sometimes you just have to call it a mystery I suppose.  I also noticed that the tank was not sitting flush on the hull in the foot frame, so there may have been some rocking working on the hoses. I corrected that issue with some well placed rubber pads before cinching it back down. 
I also added a diesel/air fuel separator while I was crawling around in the locker. Much easier with the tank out. Now the vent should not burp diesel during fills.
Fuel/Air separator

Sorry if this doesn't help. Sometimes you just need to hear from someone who commiserates... :)
Regards,~guy
Pleiades'97 C320  #452Worton Creek, MD


      From: Marek Fluder <marekf at gmail.com>
 To: "C320-List at Catalina320.com" <C320-List at catalina320.com> 
 Sent: Wednesday, June 22, 2016 9:21 AM
 Subject: Re: [C320-list] Leaky fuel tank?
  
Rick,

Thank you for your advice.
Fuel was pooling at the lowest (forward port) corner of the tank before
overflowing the foot-frame that secures the tank in place.
In the past I have sealed my leaky sender unit on the top of the tank
(another common issue).
This time I did not see any evidence of any leaks from the fittings, hoses
and the side walls therefore I concluded it must be the corner or the
bottom where I cannot see without pulling the tank.
I have snapped some pictures.
<http://www.catalina320.com/mediagallery/album.php?aid=297&page=1>
Your idea of pressurizing the tank partially filled is going to be my next
step.
I would like to have a clear evidence before dropping close to $1000CAD for
a new tank...

Thanks again.

Marek
2005 #1028

On Wed, Jun 22, 2016 at 7:56 AM, Rick <rsulewski at bex.net> wrote:

> Mark,
> I replaced my tank a year ago because I had experienced a nasty sender
> leak over the winter from an overfilled tank and did not want to endure
> another fuel clean up mess over in the next several years given the age of
> my hull (20 years) when the tank could be expected to begin leaking.  My
> reasoning was  why wait for a fuel leak that day was predictable?
>
> Based on my research of aluminum tank leaks across several manufacturers
> most diesel aluminum tanks can be expected to develop leaks within plus or
> minus 5 years of the 20th year.....a matter of not if, but when the tank
> can be expected to leak.  My review of the 320 discussion list pointed
> toward many 320 tank leaks occurring at the lowest portion of the tank's
> seam weld or the lowest portion of the wall nearest the tank's welded edge
> near the forward & portside corner area.
>
> Did you see any evidence of fuel residue in the suspected area of the
> typical 320 tank leak? Have you considered pressurizing the tank with a
> small portion of fuel in the tank? Given the 320 discussion list tank leak
> details I observed, owners seem to report evidence of tanks weeping well
> before the leaks growing worse over time.
>
> When I received my new tank, the tank's fuel filler hose was securely
> sealed with a flexible cup like cover that was pushed onto the filler inlet
> that could also be clamped to that fitting. Also, all of valves were
> closed. When I opened a valve I could clearly hear the air pressure
> equalizing within the tank, suggesting that the tank was still under
> pressure when it left the factory, perhaps due to the temperature
> differences from when it was packed or the elevation differences from when
> & where I am located. This suggested to me that the variables involved in
> pressurizing the tank where tightly controlled by the tank's sealed valves
> and the filler pipe seal and that the tank was still under several PSI for
> a sustained time.  That is why I suggest attempting to replicate the tank
> weeping with a small amount of fuel in the tank for a period of time while
> the tank is left under pressure vs. simply looking for an air leak bubble
> with soapy water.
> Rick
> 1995 320 hull #277
>
>
>
> -----Original Message-----
> From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On
> Behalf Of Marek Fluder
> Sent: Tuesday, June 21, 2016 9:30 PM
> To: C320-List at Catalina320.com
> Subject: [C320-list] Leaky fuel tank?
>
> I have pulled my diesel tank today for inspection based on research on
> this list archive and my observations of diesel showing up in bilge area
> and around the tank. All fittings and sender unit on top were dry. Now I am
> puzzled as I pressure tested the tank spraying soapy water and nothing. The
> tank looks solid. Question to listers that replaced the tank - was the leak
> on the tank obvious?
> I am stumped.
> Marek
> 2005 #1028
>
>