I had a similar leak issue with Russell fittings on a turbo oil drain. Against my better judgement, I decided to skimp on buying top dollar lines and fittings for just a drain line. I was wrong -- the damn thing leaked no matter what. I should have gone with Earl's UltraPro from the get-go, which is what I used on my entire fuel system. Yes the UltraPro line is pricey, but in the end, spend it once and be done. Let's not forget, while replacing the lines and fittings is money, your time dealing with the frustration and time spent on replacement items quickly quadruples the initial price.