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Fuel line leak INSIDE the gas tank.


letitsnow

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I'm extremely suspicious that my feed line inside the gas tank has a leak in it and it's sucking air when the tank is anything but completely full. The tank has been cleaned and coated with eastwood's gas tank sealer kit. What options do I have to fix this? I think I'm stuck either cutting it open or getting a new tank.

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Hmm.. I wonder if my car is doing something similar. When I would fill the tank most of the way is seemed to run a lot better (Tuning the carbs helped too). When you put your ear to the gas tank filler you can hear fuel trickling in the tank. Is this normal? Sorry to thread jack, but I am wondering if this is a similar problem.

 

Thanks, Elliot

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I just had my tank apart to weld on a sump, and I had a pretty good look inside the tank. The stock feed line looks like a normal soldered in pipe that runs from the wall of the tank straight down to near the drain plug, the lowest point in the tank.

 

I'm thinking a couple things could be wrong with your fuel pickup...

 

Since you said it was pretty heavily rusted, it may be that your line itself is deteriorated, or the solder on the pipe has busted, either on the inside or the outside.

 

Either way I don't think you have an easy fix with this one... if you clean up the outside, you might be able to re-solder the joint. I would do a simple check with some clear tubing on the outlet, creating a siphon into a jug, and see if you get air bubbles, or if it even siphons at all.

 

The other thing you might think about is your hoses... they don't last forever. If you took the tank out and did not replace the rubber hoses, they might not be making a good seal anymore.

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The tank feeds properly when it's full to the top, after a few gallons it starts to slosh around and I get a bubble that I can feel every now and then.

 

Thanks for the info about the lines, but I think my '77 tank is different than a '72, it's probably still soldered though. I have a spare tank that I'm going to cut open, sandblast, fix the holes, re-tube with some SS tubing, and coat with some alcohol resistant coating so I can run e85 without fear. I can tell I'll want more power later on, it's already fun at 7psi.

Edited by letitsnow
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Just to make sure I'm not a gigantic idiot, which is the feed line and which is the return line on the tank? What would happen if they were switched?

 

 

On your 77 it might be a bit different, if you have a Haynes manual around it might help. On my 72 it is really obvious, because the feed is 5/16" and return is 3/16". One way to tell is if you take the fuel sender unit out, and look in to see which one has a tube running down to the bottom of the tank, and which one does not. Obviously, the one with the tube is your feed line.

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One is 3/8 and the other is 5/16, they both run into a baffle/sump/canister in the middle of the tank. The smaller one is on the bottom both on the outside and in the tank. I currently have the larger as the feed.

 

The larger one is going to be your original feed, so you have it setup correctly.

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I wonder what would happen if I got a 3/8->5/16 barb and switched them? Not as a permanent solution, but so I could start sorting other issues out without going to the gas station every 25mi.

 

I'm not sure what that would do... I'm thinking it should at least work for daily driving, but I wonder if you would hit some starvation issues if you pushed it. In any case, if that fixes the problem temporarily, you know where to start! I'm thinking that if the pickup has a hole in it somewhere near the top, You're going to have to get in there and somehow repair the pickup, or or replace it completely...

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It helped a lot, the fuel was at a level that I had a hard time making it home last time. After I switched it I drove around for a bit and it worked pretty well, got on it a few times and everything felt good(AFR's right around my 12.3:1 goal), on the way back cruising at 60-65 it would get a bubble every now and then and drop a cylinder. :( It is an improvement, but doesn't quite work well enough. Apparently at 7psi a 5/16 line is plenty.

 

I just started cutting apart my spare tank, cut a ~6x6 hole on the top opposite of the fill neck and I'm about to go liberate the fuel lines and cut a smaller hole on the same side as the fill neck. There was a LOT of rust in it, probably 5lbs of loose dirt and rust. :blink:

 

 

Edit: I got the lines out, in case anyone is wondering, there IS a pick up filter/sock in a '77 280z tank. It's a relatively fine stainless steel mesh with a brass housing.

Edited by letitsnow
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