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Discussion Starter #1
Hello, So I have a small fuel leak at what appears to be at the top of the tank. I dropped the tank and pulled the sender unit. Looked for cracks at the sender unit pipes. Looked good. No rust. Pulled the sender unit out. Replaced the strainer and sender O ring since I was in there. Replaced the fuel line and QD connectors from the pump output to the fuel filter. Started the car up and while underneath while running I can see no leaks from any of the sender pipe connections. But after a drive there is a small amount of fuel residue on the sides of the tank and smell. Lines are dry with no leaks. So I am back to square one after a bunch of work. Any ideas? Hairline crack in the sender pipes at the very top I cant see ? Or cracked tank? At a loss. Any help is welcome. Thank you much...Uvaldi.
 

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It could be your vent hose for the filler tube.
 

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Our tanks appear to be blow-molded with less liklihood of seam issues. But any manner of leaking along the sides or top that you cannot eyeball directly from underneath pretty much requires dropping the tank in any case. Which strongly indicates the 'little pressure / soapy water test' above. You might get lucky and find the top ring is not seated perfectly, or glitches at external connections including any you replaced..

You might get really really really lucky and find the 'residue' was noticed only after the fact from the initial work, and that the 'smell' is an entirely unrelated and very common 'rotten to hell vent line transition connector hose piece'.

The positive is the R&R will be fresh in your memory and take v. little time. This time. ;)

1575296880479.jpeg
 

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Discussion Starter #6
Our tanks appear to be blow-molded with less liklihood of seam issues. But any manner of leaking along the sides or top that you cannot eyeball directly from underneath pretty much requires dropping the tank in any case. Which strongly indicates the 'little pressure / soapy water test' above. You might get lucky and find the top ring is not seated perfectly, or glitches at external connections including any you replaced..

You might get really really really lucky and find the 'residue' was noticed only after the fact from the initial work, and that the 'smell' is an entirely unrelated and very common 'rotten to hell vent line transition connector hose piece'.

The positive is the R&R will be fresh in your memory and take v. little time. This time. ;)

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Thanks for the replies. The fuel residue was "new" after a test drive. I was very careful hooking everything back up and inspected the hell out of the tank and lines. My evap line is connected and fairly new. At the connection at the top the evap hard line was kinda loose going into the tank. Don't know if that is normal for the particular line. No rust or cracks that I could see. The other two lines are solid. Could the O-ring at the sender leak even if the tank is never filled up all the way? I put in a new one when in there.
 

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From sloshing around while driving even a partly filled tank could easily leak at the ring if it ain't on perfect. When I did my new pump I did a real thin bead of dielctric grease on the new o-ring just for SAGs. I use that to seal about everything nylon or rubber since I THINK it's not petroleum based.

FWIW and FTR I've recorded a near 100% track record over the decades for successfully being able to zoom straight to the root cause of a mysterious new problem by presuming it's connected with recent work I did - unless proven otherwise. Werd yo.

BTW most all my 20-year old oem spring clamps get replaced with screw type if they show the slightest sign of relaxing.
 

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Discussion Starter #8
From sloshing around while driving even a partly filled tank could easily leak at the ring if it ain't on perfect. When I did my new pump I did a real thin bead of dielctric grease on the new o-ring just for SAGs. I use that to seal about everything nylon or rubber since I THINK it's not petroleum based.

FWIW and FTR I've recorded a near 100% track record over the decades for successfully being able to zoom straight to the root cause of a mysterious new problem by presuming it's connected with recent work I did - unless proven otherwise. Werd yo.

BTW most all my 20-year old oem spring clamps get replaced with screw type if they show the slightest sign of relaxing.


This is the O ring I used. ACDelco G19 Fuel Pump Tank Seal. Suppose to be the proper one. The old one was alot flatter, I don't know if that was just from 25 years of compression. The leak I have now is from the same exact place before I started all this work. Drivers side top of tank leaking down from what I can see underneath. Maybe a bore scope shoved up there why it is running would help me see?
 

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....... The leak I have now is from the same exact place before I started all this work. ....
Look at the bright side. At least you didn't make it worse! ;)

J/K. You may have an invisible chafe or wearthru from a heatshield or a protrusion in the floorpan, or a stress crack at the pump hole - who knows. I'd just drop the tank and be done with it. At least you'll be looking with more suspicious eyes this time. It won't take much to try Gerry's soap test once it's down, even using a bike pump. If you got anyone nearby then have them look things over too. Some things are so obvious you don't see them yourself. lol
 

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If you suspect the tank ... absolutely the soapy water test ... bubbles tell all. Does your tank build up pressure after a drive? If you take off the fill cap, does pressure escape?
 

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Discussion Starter #11
If you suspect the tank ... absolutely the soapy water test ... bubbles tell all. Does your tank build up pressure after a drive? If you take off the fill cap, does pressure escape?

Been away on work so I don't know yet if the tank is pressurizing. Will let you know. Thanks for al the replies. Gotta get this fixed for sure...
 
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