Sealing threaded brass fittings in fuel lines?

[BHW]

I had to jury rig a new fuel line on my bike, and ended up using brass connectors, I had to thread two together. I asked at the auto parts store about sealing the threads, they said just get them tight. I've heard that teflon tape is a no-no in fuel lines. Is there anything else, other than having a gorilla use a cheater bar and tighten them up. My first attempt resulted in seapage from the joint.

[malbojah]

There is a type of Teflon tape that is used for fuel applications. They may even carry it at that auto store that told you some bad advice.

[FastCat]

Teflon® tape (otherwise known as PTFE tape) was developed for steel water pipes with tapered threads.  If you have tapered threads on a brass fitting, teflon-tape is an acceptable way to seal them, but the problem with teflon tape is that shreds of the teflon end up inside the system and you can just imagine what that would do to the float-needle if it gets hung up in there...

Loctite (and others, I'm sure) makes a thread-sealant that's similar to the thread-locker stuff.

[BHW]

Well, I'm now convinced that bare brass fittings won't hold fuel. I used spark plug sockets and long extension handles, and torqued the fittings as tight as they would go, and they still seap gas.....so that won't work. And it worries me that what ever I use to seal the threads will be exposed to constant gas...and might end up running through the engine.

[JimWilliamson]

I, um, have used some rather shady shade tree mechanisms from time to time. One popular one for those - seal-m-up once and for all projects: Put some two-part epoxy on the threads as thread sealant. Tighten as you would reasonably expect. Wait 24 hours (or so) for it to set. Test.

I put it on the threads such that it should not extend / come into contact with the liquid in the lines.

 

[TuffguyF4i]

What kind of a fitting are we talking about?  Compression fittings with the small cone inside to make the seal?

[BHW]

Obviously not my photo, but they look similar to this:




I have two sets of threads, one set I screwed in all the way, as far as it would go....it took some torquing and cheater handles on two sockets. The other piece I broke off trying ot torque down, so I backed it out and used a spare, tightended it as far as it would go, still has threads exposed, but it won't turn any farther. So, without some sort of thread locking sealant, the brass simply won't hold fuel.

[bomber]

+1 on the designed for fuel application thread sealer -- comes in a tape form, and a viscous, semi-liquid, goodey form -- either work

ps, find another auto parts store, or talk to another employee -- the first one gave ya bad info

[veefer800canuck]

Yes, there is Teflon tape for petroleum products. We use it all the time in the oil and gas industry where I've worked for the past 24 years.

As far as shards of Teflon tape getting into the fuel system, just don't wrap it over the end of the fitting all the way and then some, leaving loose ends dangling in the system fluid.

Leave a thread or so exposed at the end of the fitting and wrap upwards from there. Two or three wraps should be fine.

Also be sure to wrap the tape in the same direction that the threads run so that when you tighten the fitting, the tape will not unravel.

[BHW]

I found the yellow teflon tape at Lowes....says "for use in gas applications". Thanks, I'll try it and see what happens.

[Jetpilot5]

That's for black iron pipe used in natural gas applications.  I don't know if it will work with gasoline going through brass fittings or not.

[Uncle Bob]

this is something I deal a lot with, since my turbo projects have a lot of fittings in the fuel system.  The best answer is tephlon PASTE.  You can pick it up at any plumbing/hardware store.

But the autopart store was correct....the sealant is just added insurance.  Assuming the threads are clean and you get them tight, you shouldn't NEED anything to seal it