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Fuel Tank Leaking on top


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Hey, so my gas tank has been leaking only when I fill up completely. I just swapped out the gasket for the pump housing but I am realizing that the issue is likely the seal that chipped away for under the stud ring is where the fuel is leaking. I am holding up the old brittle sealant from around the stud ring in both pictures. Seems silly to replace the entire tank for this. So I am considering trying out resealing it on both sides of the ring with either of the following. The red arrows in the second picture indicate both sides I would attempt to seal.

Option 1. Option 2.

Any thoughts on this or maybe better sealing material? If not then I am just going to ship it and try it out.

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11 minutes ago, Enlight said:

I can't quite make out what has chipped off from those pictures, but you can try using Permatex Fuel Resistant Dressing next time. Also, is this a crack where I have circled?

So what has chipped away is circled in yellow and used to live where the right arrow is pointing. It went all around the metal stud ring but has all chipped up. That is why bare metal is visible on the outside of the metal stud ring. I'll give the permatex a look. As for the crack, I can't 100% say it isn't because the whole thing is back together now but I am pretty confident it is not. The rust stains are just from the metal clamp on top having some rust. When I try the "bigger the gob, better the job" on this with either the JB tank weld or the permatex, I'll make sure to remove the fuel pump assembly for best access...just have to drive it for a while now since I just filled it up 🙃

To add to the fun, the middle fuel send line had its retaining clip break so its only retained by half the clip now...advance has a dorman part that I am hoping works to replace the clip. I am trying to lay down some serious miles this summer with this car!

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I'll update this with however I end up fixing the leak. Not too worried about it. But the clip for the fuel pressure line is fixed (replaced). 3/8 quick connect clip replacement from dorman. 800-016. Hopefully this helps for anyone looking as the plastic gets old and brittle in these cars.

Dorman Fuel Retaining Clip, 800-016 800-016

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Well I failed successfully. I did all the prep work (sanding, cleaning) all while making sure the tank was sealed off to not contaminate the fuel. From what I read JB Tank Weld seemed to cure quick (I've used JB Weld plenty in my day and am very familiar with the work time + mixing ratio). I shouldn't have read anything as I didn't mix in all the catalyst (I used about 75%). 8 hours later, it is still a little tacky...F. As you can see the application is on point! Now I have to try and rip up the tacky stuff and redo it. I am really hoping it peals up or somehow I get home from work and now its suddenly fully cured.

This also has me thinking that the leaking is also related to bad pressure relief valve. I did have some evap codes 3 years ago that I ignored and just turned 'off'. That might be biting me in the ass now🙄

If this repair turns futile, then I might be dropping the tank this winter and replacing all the hoses around it related to evap like I should have 3 years ago when I last had the tank out!

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So good news, I got home from work and the JB Tank weld had stiffened up quite a bit. Not exactly as hard as I would expect but way better than it was. No residue is being left on my fingers anymore. Either way, it is far too cured to try and remove it so I guess I'm just going to stick with it. I did notice while cleaning off the plastic flange of the fuel pump assembly that it has a few cracks / is being eaten away at the corner. Not super worried but maybe that is a project for this winter to replace. Last, I notice the insulation on one of the wires for the temp sensor had a hole in it. Since it is the only exposed wire I am not worried about it I don't have fuel safe wire / heat shrink, so again a project for another day.

Final thought, for those who upgrade the gauge wire from the fuel pump control module, are they also upgrading the wire in the tank? Just a thought as it is kinda silly to do one and not the other. (Just me and my shower thoughts)

 

Long post made longer. I plant to button it all up and test the tank tomorrow night. I'll report back

 

 

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  • 2 weeks later...

Replaced my tank a couple years back after it would leak when nearly full. Was leaking due to rust penetrating and peeling open the welded seam. Also discovered a rusted off nipple for the tank pressure sensor. Other people have had similar failures so might be worth checking your tank for these issues. Posted a tank autopsy here with lots of pics: https://www.subaruoutback.org/threads/whats-inside-fuel-tank-edition-leaking-fuel-tank-autopsy.510193/

What wire gauge is on the inside of tank? What is the amp draw of the upgraded pumps?

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So I am familiar with the seam leaking due to rust. Thankfully that is not the issue here. I think the ring with the studs warped or something. The combined application of the JB Tank weld on the inside of the ring, and using Permatex 85420 (fuel resistant gasket dressing). I applied the permatex to both sides of the rubber seal and let that set over night. The nice thing is that it is not permanent as it never fully cures and just remains tacky so removing the fuel pump will not be an issue. 

I filled the tank up this morning and drove to work, bone dry!!! I'll keep an eye on it over the next couple fill ups to see how it holds up.

This will hold me over until I can drop the tank, test the pressure sensor, test the pressure relief solenoid and replace all rubber hoses.

 

As for the wire gauge, I am not sure. Eye balling it I'd say something like 18 or maybe 16 gauge. Either way, I know some people upgrade the wiring from the control module but I don't hear about the wiring in the pump being upgraded too. It is far shorter than the wiring from the control module so the voltage drop across the length isn't as large.

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14 hours ago, jaylew said:

I filled the tank up this morning and drove to work, bone dry!!! I'll keep an eye on it over the next couple fill ups to see how it holds up.

LOL...jk. It was bone dry from fill up and the entire drive to work (36 miles). Come out of work at the end of the day and did a check. Suffice to say, I am not out of the woods yet. My thought process is to live with it for now, diagnose the purge solenoid (make sure it is working) and then address this in the winter after I move into my house. Drop the tank, replace evap controls and rubber hoses and maybe fuel lines as longevity insurance.

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The surface that does the sealing is the inside ring, I don't think sound dampening stuff on the outside that you repaired does anything in regards to sealing. The gasket seals the bottom of the assemble, that lip, and that inner metal ring. And if the fuel is coming from that seal, I would check how straight the underside of the fuel pump hosing is and the straightness of the metal ring sealing surface. But with the thickness of that gasket it should be able to eat any of the unevenness.

Next time it leaks if you pull the fuel pump right away and inspect the gasket, it should be still wet hopefully, that should help zone in on the problem area.

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Ok, so upon further googling and actually looking at the service manual exploded view, it appears the stack up (bottom to top) is Tank-gasket-pump-clamping ring.

idk how this leak has only just now manifested but when I started looking into it (mind you this has been the first time I have touched the fuel pump) the stack up was Tank-pump-gasket-clamping ring.

I am going to return to this in a day or so and by rearranging the stack up and see if it is still leaking after that. I will feel so dumb but also happy if this is the solution...just proper install haha

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Check this video at 4:00 minutes! It will show you exactly how the gasket should be orientated. The gasket goes in between the tank and pump, and the clamping ring goes on the top of pump. If you have the gasket on top and its just plastic and metal making a seal then I am pretty sure that's why your leaking fuel!  

 

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Yup this is the exact video i was just watching. I am very curious how it hasn't leaked for so long but now all the sudden it is. I'll update if this fixes it which i am very confident it will. Thank you for the help!

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I think you can use fuel line hose to replace the rusty metal evap pipes, if that's your issue. 

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I might be posting too soon, again. But just filled up this morning after correcting the stack up last night. Dry on fill up, dry on drive in, and just checked after sitting for 4 hours and still dry. I'll check again after work but so far it's looking good. I am still baffled how it might have been originally installed incorrectly.

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On 8/22/2022 at 1:47 PM, Max Capacity said:

I think you can use fuel line hose to replace the rusty metal evap pipes, if that's your issue. 

I did a little of that when I pulled my tank for R&R. Worked a treat. Just used carb line since it's far cheaper and more than enough to handle the EVAP system pressures.

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20 minutes ago, jaylew said:

I might be posting too soon, again. But just filled up this morning after correcting the stack up last night. Dry on fill up, dry on drive in, and just checked after sitting for 4 hours and still dry. I'll check again after work but so far it's looking good. I am still baffled how it might have been originally installed incorrectly.

 

Are you the original owner? If not could have been someone just doing bad work or maybe you brought it in for diagnosing at some point, and someone went in there for some reason. That broken piece on the outside you first thought was the problem might be a sign that someone was in there previously. Otherwise someone was hitting the sauce at the factory lol! 

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I have never done the carfax and I bought the car off an auction flipper back in 2015. I believe I am the 2nd owner since I have a lot of the original paper work (window sticker, all keys and their security tags, the dealership delivery checklist etc). My current thought is the pump was removed for some reason by prior owner but the sound deadening I pealed off was keeping it sealed. Now that the sound deadening was degrading, the fuel had somewhere to leak. IDK just a theory but it would have had to be this way for at least the past 7 years. I could be crazy (all the fuel fumes and what not, thankfully its not leaded still)

If it no longer is leaking, I am still motivated to replace the evap lines and fix my evap codes this winter. Cheap project (unless the pressure sensor is bad)

Thank you for the help and input everyone!

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