| Finding fuel tank leaks. [message #369990] |
Mon, 20 June 2022 21:41  |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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I had a leak in one of the two tanks. I could smell it but the only time it would drip is when I’d fill full. So I dropped both tanks. Each tank has two vents. A vent nipple on the top of th tank and a vent the sending unit. I found the first obvious leak at the reserve tank vent where the hose slipped off of the reserve tank vent nipple. So I then plugged all access points on the tanks and pressurized the tanks. Then took soapy water to every connection. The next leak I found was at the main tank. There was a pin hole leak where the vent nipple is soldered to the tank. Cleaned it up and applied JB weld. Finally, I have in-tank pumps and found leaks around where the vent comes out of both sending unit vents. Cleaned up and JB welded it. While it was apart I replaced the fuel pump strainers, (AKA “socks”) and sent the tanks out for cleaning. I know most people think that dropping tanks is a difficult job. But even with the extra wiring and steel line connections, the whole dropping thing, start, to tanks on my work bench took about 1 1/2 hrs. Spent most of the time waiting while pumps drained the tanks into waiting 5gal gas cans. The most interesting thing about draining the tanks was, after pumping the tanks dry, and the tanks were out, I tipped the tanks on their side and poured out the excess fuel that the pumps would not take. Total fuel remaining in both tanks when pumped “dry” was only 1qt. Yes, your read that right....1 qt. Amazing…thought it would be more than that. Waiting now for my tanks to come back from Irvington Garage. JWID
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: Finding fuel tank leaks. [message #369993 is a reply to message #369990] |
Tue, 21 June 2022 08:01  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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I found the same thing. Using an electric pump takes time, but once the tanks are drained that method they are virtually empty. The one time I drained tanks using the drain plug(on steve's lift), I got a surprise bath in fuel when we started pulling the tank down.
those vents are a weak link on the tanks, the one you mentioned I have seen loose before.(Ed's). and I have seen many examples of the vent nipple loose and needing to be jb welded.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: Finding fuel tank leaks. [message #369994 is a reply to message #369990] |
Tue, 21 June 2022 09:59 |
dsmithy
Messages: 210
Registered: July 2012
Location: Lincoln Nebraska
Karma: 0
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Senior Member |
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Larry,
What are you going to have Irvington Garage do?
Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
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| Re: Finding fuel tank leaks. [message #370003 is a reply to message #369990] |
Wed, 22 June 2022 07:57 |
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RF_Burns
Messages: 2276
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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I had the same issue with a leak only when the tanks were full. I replaced the loose cinched in vent line with a brass one and J-B Welded it in place. Its been about 6 years and no more issues.
I also installed metal lines on top of the tanks. Good thing because I noticed the fill vent hose jumper was breaking down. It was an easy quick fix with hopefully better quality hose.
http://www.gmcmhphotos.com/photos/g7006-fuel-tank-lines.html
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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