Nylon Tubing and Barbed Fittings

It is recommended to use a compression fitting when using nylon tubing as a fuel line. Nylon does not grip a barb fitting well. It's not pliable enough to contact around the barbs. If you wish to use nylon tubing replace the barb fitting with compression fittings. If the barb fitting is to be used recommend Tygon or other pvc tubing rate for fuel.

Thank you for the reply. One question. The car comes from the factory with the spring-loc fittings (barbed) stainless steel to nylon on the fuel rail

and plastic barbed (duckbill or d-lock) to nylon hose on the fuel filter. How is it recommended to use compression fittings when it comes from Detriot like this? Thanks.

Are you sure it's nylon?

I am fairly certain it is nylon. And can be purchased in bulk or can buy a repair kit to be spliced with barbed style fittings:

EFI Nylon Fuel Line Tubing

"This is same tubing that Ford uses on their fuel injected production vehicles
To be used with Stock Ford Fuel Fittings
Safer than steel tubing
Sold by the Foot"

AND

Dorman 800057 Nylon Fuel Line Repairkit

Did you try a heatgun or hair dryer may work to get the tubing pliable enough to push over the barbed fitting?

Boiling water usually works, but don't dip too much of the end into it else you no longer have a stiff tube to push, it also takes a minute in the water to soften it. Sometimes cutting the end of the tube at an angle will help get it started.
I do however agree with those who say that nylon isn't ideal for push on as it doesn't have much memory.
It's used a lot for pumping rinse aid in comercial dishwashers etc, and rinseaid is good at finding gaps, also it's pumped at 2-3 bar quite often.
Del

Ok I agree with Del (as always) but I would still like to know how these are manufactured\assembled....heat gun perhaps? And at what temperature.

I plan on simply cutting off the nylon line and using a 5\16" line with stainless steel ear clamps for that factory look. The hose I have in mind is Polyethelene Tubing with temp rang -50-140deg and psi rated at 125. But there are many options...High Density Polyethelene, Polyurethane, Flexible Polyethelene, etc... I suppose I could be over doing it and should just go to the local auto patrs store and ask for standard EFI fulel line and be done. Any suggestions as to the fuel line type?

If you are pushing onto metal fittings...get the metal fitting warm too.
Del

You should check out how PEX tubing is installed. It uses an expanding collet to to open the tube end and when removed, must be installed onto the fitting very quickly.

I will investigate PEX. I boiled the tubing for about 5min. with no luck. I have ordered some samples and will try installing new virgin tube. There are many options as far as ID and wall thickness plus metric sizes also available. I will mic my fittings and see which one of the samples best fits my application. I have a feeling the stuff I am working with has reached its useful life...1993 Mercury (16yrs.)

I work with fuel lines all the time. The best way I found to push the hose over the barb is use a little mineral spirits and a plumbing flaring tool. Lay the end of the hose in a small cup of mineral spirits for five minutes. Then grip the hose directly beneath the area where the barb will end up and tighten the flaring tool like it were a piece of copper tubing. Next use the other part of the flaring tube tool (the spinning flaring end) to push the barb into the tube like you would be flaring the end of the copper tube. Works like a pulley puller but in reverse. It pushes the barb right into place and it won't leak or come off. Good Luck.

I'll give you a GA for that.

Picture in post 6 shows an assembled fitting. It appears this is the way most of the kits are sold... there must be some special assembly jig used to accomplish this. Your solution sound reasonable, do-able, and he probably has a flare tool already. jturley, please let us know of success / failure of this idea, would you?

Yes I will try this tonight and post results. I do have the flare tool in the garage but never thought of using it that way. Thanks for the ideas. Jim

I'm afraid the tool might cut into the tubing when tightened around it. Those little serrations on the inside of the jaws will bite right into the tubing and give you a perfect failure point.

Just a thought, never done it myself.

I thought I might use a piece of tape to protect the tubing.

Use a heat gun to warm up your tubing, carefully though.

Nylon has a melt temp of 490-520 deg F. Boiling water at 212 is still a little cold. A heat gun should help. The factory probably has heat lamps and a special fixture to push these togeather. Good luck.

I am going to borrow a heat gun today and give it a try. I tried using a brake flare tool to hold the nylon tube and to get a little leverage but it had the same effect...none! The 212 water does soften the nylon but not enough. Thanks.

You might try something like this tool:

http://www.speedwaymotors.com/Push-On-Fitting-Tool-AN4-AN6-and-AN8,941.html

The problem with nylon is that it is a semi-crystaline material. This means that most nylons will change from a stiff solid to a liquid within a very short temperature range. In a production environment, the tubing (if it is nylon) is probably heated to a precise temperature before being pressed over the barbed fitting. As another poster mentioned, boiling water is not hot enough to accomplish this job. Using a heat gun may not bring it to the precise temperature to allow the tubing to stretch without melting.

Just a thought, you may have to heat the tubing and the barbed fitting both to be able to assemble them. A cold fitting may pull the heat out of the tubing too quickly to assemble the tubing.

For many years, that type of fuel line was used on Jaguar E Types and is readily available from restoration supply houses such as this. They can also instruct you on the technique to install it properly. I would caution that when this hose was used, pump pressures were typically 5-8 psi or so. If you are using this for a fuel injected system, it may be seeing 40 psi or more. Personally, I would contact the dealer and have a mechanic tell you what is involved in installing it. Or just use quality hose clamps and be done with it. I realize it is a specially designed connector. It probably requires a specially designed replacement part. We don't want any carbeques.

I'm taking the time to write this response because when I looked for the answer to this problem on the internet I couldn't find it. I just went through much more time and money than is necessary trying to fit a new line connecting the fuel rails on my 4.6 liter Ford. That nylon fuel line is not cheap and it's easy to waste a lot of it trying to figure out how to use it.

First, your best bet is to buy a large quantity of it. Dorman offers 10 and 25 ft rolls of it for about $10 and $20 respectively on Amazon. Look up the part number that you want on Dorman's website first. The local auto parts stores carry small pieces but they want $20 a foot which would be fine if you only use a foot but the learning curve is steep on this material.

Next, forget hot water (like the manual says) and go buy a cheap heat gun. I got one from Harbor Freight for $15. Even with the heat gun, I couldn't get the nylon tubing over the barbed fitting without kinking the tubing or burning holes in it so I used a barbed fitting that came with one of the "repair kits" that I wasted money on and some remnants of the tubing that I screwed up to practice technique.

Finally, I figured out how to get the tubing onto the barbed fitting easily and consistently. I found that using the heat gun on the high setting worked best. Simply put the tubing at the end of the barbed fitting with very minimal pressure then use the heat gun to heat the very end of the nylon tubing being careful to not heat it so quickly that it starts to burn. I'm not sure but it may be that heating only the very end of the line actually meant that I was heating the fitting and that's what makes the technique work so well. The Nylon tubing will start to soften and the slight pressure that you have on the line pushing onto the barbed fitting will start to walk it on. Keep the heat mostly on the end of the line as it walks on to the fitting and don't try to force it or you'll kink the tubing; just let the heat do the work. When it gets to the bottom, stop.

When it cools, you'll have a fit as good as the factory and your line will be perfect. If you took my advice and bought the line in bulk, you'll have plenty to practice with and can afford a few mistakes. Practicing on the bench is a good way to learn how to work with this material.