Pro tip: I tried using a regular socket on a Cummins ISX fuel line fitting and it was a comedy show

Had a 2015 Freightliner in the bay last week with a weepy fuel line. My good flare nut wrench was on another job, so I thought, 'how bad could a regular 12-point socket be?' Bad. Real bad. I got it on there, put some pressure on the ratchet, and the socket just rounded off the fitting's corners like it was made of butter. Spent the next hour trying to get a grip on this shiny, smooth nub I'd created. Finally dug out my old, beat-up snap-on flare nut wrench, the one with the super thin walls. It bit right in and the fitting came loose with a normal grunt. The difference was night and day. That thin wall on the right tool makes all the space it needs without slipping. Anyone got a good trick for getting a rounded fuel fitting off when you're already in that deep?

3 comments

3 Comments

wood.zara3mo ago

Ugh, been there. Try a small pipe wrench if you can get it on there, the bite can save you. If it's totally stripped, sometimes you can hammer a slightly smaller 6-point impact socket onto it for a last-ditch grip.

hollypalmer3mo ago

Actually @wood.zara, a pipe wrench can round it off more, so maybe try vise-grips first.

gonzalez.rowan1mo ago

Hold on a second. I'm gonna argue the other side here. I've been using a plain old six point socket on ISX fuel lines for years and never had a problem. The trick is you gotta go slow and use some penetrating oil first, not just reef on it like a gorilla. If you're rounding them off, you're either using too much torque or you're not holding the wrench right. Flare nut wrenches are fine but they're way too bulky for tight spots and they slip just as easy if you're not careful. Honestly, you probably just got a bad fitting or some rust on there, not a tool issue. What kind of penetrating oil do you usually use?