Alright guys, what's the rule of thumb for using teflon tape on fuel lines. I bought a set of steel braided fuel lines a few years back and I "thought" the guy said no teflon tape was needed. Regardless, I've never leaked a drop of fuel. I've been looking into a few different rail mount and underhood mount fuel pressure gauges, and they all say to use teflon tape around the fittings. Gauge or not, I'll be pulling the fuel rails to have the injectors cleaned and benched, and to add the AFPR. I'm gonna remove the braided lines during this process, and I'm wondering if I should use teflon tape when I put 'em back on? Maybe my no leaks are a fluke, and I just got lucky?

Anyone have an opinion????

 

The rule of thumb is to never use teflon tape, but to use liquid teflon only on pipe threads. Flared or O-ringed fittings don't need a sealer.

 

Thanks for the quick response. I actually posted an almost identical question back when i originally got the fuel lines!!!

....turns out you guys are still full of good advice. Guess I shoulda searched first and THEN posted!!! Most things I learn over the years and never forget, but with fuel and hot headers in close proximity, I'd rather ask twice!!!!!

Thanks again.

 

the gasoline will actually dissolve the teflon tape. common misconception is that teflon tape is a "sealer" when really, teflon tape and liquid teflon are just lubricants for the threads. its the threads themselves that seal the fittings together.

 

No, NPT pipe threads do not self-seal. Only NPTF threads do because they're an interference fit.

 

OK, no dumb questions, only dumb people.

What does NPT and NPTF mean?

....and I've been doing some reading, clearly the AN fittings with O rings don't need any liquid teflon. Does it hurt?

 

AN fittings don't have O rings. Putting sealer on the threads of a flared fitting like an AN or JIC fitting could prevent the parts from mating properly and lead to a leak.

NPT is an acronym for National Pipe-Tapered, part of the ANSI standard describing pipe threads. There are also straight-thread NPS pipes. NPTF stands for National Pipe-Tapered "Fine", describing the interference fit.

 

Alright, the internet is my friend. It's just not as fast as apeiron!

....seems the threads on the NPTF fittings are ever so slightly different to allow for a better seal, hence the interference fit.

....and it's the taper on the AN fittings that form the seal. And yeah, no o-rings on AN. I was thinking of the factory fuel line's which DID have o-rings, but are NOT AN fittings.

But you guys knew all this already. Not me. I'm learning. This stuff comes up all the time while underhood, so I'm glad I'm gaining some knowledge, instead of simply doing what I'm told!!!