Return Fuel Line Weeping

[phileas_fogg]

My return line is weeping fuel. Not enough to drip, nor even to wet your finger. But when I wrap a paper towel around the fitting after then engine has sat a couple of days, I get residue.

https://farm5.staticflickr.com/4392/36757368036_965703a488_z.jpg (https://flic.kr/p/Y187UL)IMG_4061 (https://flic.kr/p/Y187UL) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

I unmated the fitting ends to see if anything was cracked or deformed, but everything looks OK (at least to my untrained eye). I gave it an extra 1/8" turn, but it still weeps.

I'm using a 90* -6AN fitting on the flex line which mates to a -4AN Reducer, -4AN Tube Nut, and -4AN Tube Sleeve that's on my 1/4" hard line (I flared the hard line at 37* to match the AN spec); all fittings are Cobra Earl Super Stock. You can see a picture of the set up at the lower left of the picture below. The return line is the one in the foreground.

https://farm5.staticflickr.com/4292/35455684324_472a069e1c_k.jpg (https://flic.kr/p/W26DG9)IMG_3790 (https://flic.kr/p/W26DG9) by jhsitton (https://www.flickr.com/photos/91016165@N07/), on Flickr

Based on the pattern of residue, I think the leak is where the 90* -6AN fitting meets the -4AN reducer, or perhaps the 90* fitting is bad. I'm afraid to tighten the fitting any more because I've heard AN fittings can be damaged from overtightening.

Anybody got any ideas?


John

[CDXXVII]

If you feel it's at the AN fittings you can use Earl's Performance Conical Seals.

I had a -6 an fitting that I could not get to stop weeping and these did the trick.

These are the ones for -6. They are available in all the popular sizes.

https://www.summitracing.com/parts/ear-169106erl

[weendoggy]

You can try some fine lapping paste to see if it helps. If not, you have a bad mating surface and/or fitting, and/or flare. You need to find out exactly where the leak is to repair.

[phileas_fogg]

Thanks guys. I'm going to try the conical seals 427 recommended first. If that doesn't fix the problem, then I'll replace the fitting on the hose, and then the hard line.

I should have mentioned, the line itself tested well to 55 psi. That & the residue pattern tells me it's not the hose-to-fitting union causing the leak.

Cheers,


John