If your are using pipe thread you need to specify NPTF , the 'F' is for fuel, aka dryseal... If it's some other type of fitting, it's being installed incorrectly or there is damage to one or more components of the fitting.
Never had an issue sealing any fuel. Use the correct components and any liquid will seal. The only issue with the corn fuel is hose and carb rebuild materials like accelerator pumps. And drive em more so it doesn’t set up
I built my fuel tank, SS, and put in a ss npt drain with valve. teflon did`nt cut it, nor another supposed fuel sealant. Learned something new today with nptf fittings. But that black permatex stuff will seal anything. Good thing I put in a drain, cause I had to do it twice before I finally used the nasty black stuff. It works. px#80045
Others here will disagree about teflon tape, but if it's put on the right direction, wrapped tight, and the wraps are started just slightly back from the end of the threads it has always worked fine for me. I typically wrap fittings with 2 to 3 wraps on the sizes of fittings you'll find on most car "plumbing". Lynn
Inverted flare seals on the seat an a sealant is useless. Something I've been doing for years and it works great is put an o'ring in the size of the seat in the base of the female end. It works fine for gas and oil cooler fittings. (do not try this on brake fittings)
Eventually , the gas will dissolve the tape . Using a TFE paste on threads helps prevent galling lubricates the threads & allows Pipe threads to be tightened tight enough to seal . Paste used on the threaded part of flare fittings & compression fittings provides the same benefits . the paste or tape should not be relied upon to act as a sealer .
I'm in the no sealer camp for NPT and fuel. There is certainly more potential damage that can occur by using than not, barring a fuel leak on to any ignition source. What is the condition of the assembled components? The simple fact is pipe threads have a finite life for assembly/dis-assembly especially when you talk about sizes below 1/4" and in non-ferrous materials. They seal by wedging the threads together and over time the threads distort, or once if you are heavy handed. So if you are trying to get a steel fitting to seal in a die cast white metal fuel pump housing, the female side in the pump may be past it usable life. The other common leak point would be in welded bungs, again especially in smaller diameters, the bung distorts while welding. Any more details on what you are trying to do?
Edit. I just used some permatex thread sealant on a q-jet inlet. The correct seal was missing. Isn’t leaking after 1 day.
I'll defend my experience and opinion with this from a webpage "Everything You Need To Know About PTFE Tapes" PTFE tape is both oil and petrol resistant due to its notable chemical inertness, which is why it’s commonly used to seal and lubricate joints around fuel lines in automotive applications. Plumber’s sealing and lubricating tape also copes particularly well under the rigours of fairly high heat demands (see temperature performance section below) and high pressure, further underlining its suitability for use in environments where it’s likely to be exposed to oils, petrols, diesel and other fuels. As with most applications of PTFE tape, it’s considered good practice to begin wrapping slightly below the first line of threading, such that you leave one full circumference of thread exposed at the insertion end of the mating joint. In the event that any small pieces of PTFE tape are sheared off where the threads bite together, starting your wrap slightly back from the endpoint will prevent these tiny scraps of material from making their way into fuel lines or connected tanks. Lynn
I grew up in a busy family shop working on V-8 rwd stuff. Used tape on all transmission lines, fuel fittings etc. Did not have time to go back and fix a leak it is just standard procedure. But the key is in knowing what you are doing when applying the tape. No way for it to cause problems if done properly.
Been talked about...a bunch. I just use engine oil. Wipe clean, add a little oil, assemble and tighten. Never had a leak. Mike
Add this to your google search copy paste. I learn something new every day. white plumbers tape on ss will not hold up. Evidently their`s a tape that supposedly will. The colors mean something, but the meaning has changed over the years so some info may be old. The CURRENT standard is: White = single density tape and is ONLY good for small fittings up to 3/8 in. pipe. Most people are unaware of this. "Double Density" tape used to come in white as well, but because that could be used for larger pipes, it was impossible for inspectors to know if the white tape used on 1/2" and larger pipe was in fact double density, so they stopped making it. Yellow = double density, required for natural gas (methane) piping 1/2" to 2" dia. pipe. In many jurisdictions you MUST use double density tape on gas piping, so inspectors will look for yellow. Pink = triple density, required for NPT threads 1/2" to 2". Again, most people are unaware of this change and hardware stores rarely sell it for the DIY market, but if you are going to get an inspection, this is what you must use now. This is also good for gasoline and propane lines. There is also green for medical gasses (oil free tape) and gray / silver for use with stainless steel and aluminum pipe (has anti-seizing compounds embedded in the tape). Over 2" you must use sealing compounds My ss threads are fixed with sole use of the black permatex and I do not fix what is not broken. Everyone can use what they want, I found what worked for me.
I haven't noticed any difference in what it takes to seal threaded fittings with modern gas, compared to old gas. Huh.
I use Teflon plumbers paste. It’s made for water or gas line use. It’s a yellowish color, it doesn’t get hard but does firm up a bit. Never had a problem with it on steel, brass, plastic, or aluminum threads.
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