Fuel line fittings

[cranetruck]

The two different types of fittings shown here are used on the multifuel engines I have here to look at.
What are the pros and cons? Is a special tool needed to install the top one?

 

[devilman96]

Bjorn the top fitting is just a barbed fitting with a collar at the top, the hose simply pushes on, the collars make the fitting look special but its deceiving... nothing more than a stop ring...

I would say the lower fitting is the better deal with the exception of not being able to reuse the crimped collar so easily but It will hold more pressure...

 

[nickd]

A local hydraulic repair shop can sell the bottom hose and the fittings if you bring it in.

 

[jasonjc]

The bottum one you can get at a plumming store also

 

[houdel]

My local auto shop also has the lower fittings. You can buy the flare nuts and rings individually, they also stock both male and female pipe to compression adapters. Nice thing about compression fittings is if the ring gets too beat up from repeated assembly/disassembly, you usually have enough slack in the hose to cut 1/4" off the end, slip on a new ring and nut and have a brand new fitting again.

 

[WillWagner]

The top one looks like a flare fitting, does the nut turn around a sleeve? The bottom one is a compression fitting. It should have a stainless insert in the line side so the brass colar around the line seals the line/sleeve and the nut seals the outside. Pros and cons...flare fitting pros, almost unlimited re-uses, easy to disassemble and assemble, cons...prone to cracking at the flare due to vibration, if you bend them, tough to get them back into their original shape/position to get them into the fittings with no binding..see cracking above, hard to repair if they crack, break or get a hole in them. Compression fitting pros...flexible, light weight, good for plumbing things that don't line up or running long distances, easy to repair. Cons...limited reuse, they get brittle after time,( the older, non braided type), lots of different types and sizes, hard to find if it's the real old plastic stuff fails 'cause the fittings nowadays are different than the old school stuff.

 

[rdixiemiller]

Bjorn
The compression fittings are good for the nylon or teflon lines. They will also work with copper tubing. If you get Swagelok or Parker Bitelock fittings (2 piece ferrules), you can go over 3000 psi with SS tubing. There is a plastic or brass sleeve that can be pushed into the plastic tubing to prevent it from collapsing. Overtightening a compression fitting can ruin it, the ferrule will expand the fitting enough to wedge it in the nut.
I use various compression fittings extensively in paint systems. The 37 degree JIC swivel fittings have their place as well. Nylon tubing is available at good prices from McMaster Carr (www.mcmastercarr.com). Tubing is sized ODxID. Get nylon 11, it is diesel proof, tough, and cheap. It is strong enough for air lines, nice and flexible, and comes in a variety of colors. I used Nylon 11 for paint lines. These lines carried every kind of powerful solvent we could find (Xylol, toluene, MEK, MAK, etc) without bursting.

 

[cranetruck]

Thanks guys! I'll be using the compression fittings to rework the fuel system on the 8x8. And "nylon 11" for the lines. Tubing on order...
Got a final filter canister coming from Memphis Equipment along with a fuel cut-off solenoid.

 

[Rattlehead]

where to buy nylon line?

Where do you get "nylon 11"? Is this the same stuff that is sold at the big home improvement stores? Thinking of replacing all my fuel lines to prevent problems due to unknown age.

 

[cranetruck]

RE: where to buy nylon line?

As suggested by Robert above, http://www.mcmaster.com/. I got part number 5112K65.
I reused the old fittings with new ferrules.

 

[houdel]

RE: where to buy nylon line?

I don't know about "Nylon 11", but most of the local hardware stores like True Value and Ace and many auto parts stores have nylon tubing in bulk in many sizes. I suspect any of these would be an acceptable replacement for "Nylon 11".

 

[vbrescueman]

RE: where to buy nylon line?

I had one of the old nylon/plastic lines burst while driving down canal rd. in Chesapeake, VA It was the line running from the pump up to the cold start heater...quite a mess lost about 12G of fuel. Replaced all my fuel lines w/ rubber and barbed fittings but now I have a prime problem... I keep losing it- have to use ether to start up. Changed all filters except preheater filter(thats next) but I believe I have a slight air leak somewhere on one of my new rubber lines... any suggestions greatly appreciated.
Am also having a hard time getting mt oil gaskets to seal properly and I am unsure of the proper install of spring/cup assy in can... anybody got any pics? I put it back together the way it came apart but rear gasket/can won't fully seat???
Thanks,
Doc

 

[cranetruck]

Re: RE: where to buy nylon line?

....
Am also having a hard time getting mt oil gaskets to seal properly and I am unsure of the proper install of spring/cup assy in can... anybody got any pics? I put it back together the way it came apart but rear gasket/can won't fully seat???
Thanks,
Doc

One thing I can suggest is that you don't twist the canister when you seat it on its gasket, just apply pressure and tighten the nut (bar).

 

[vbrescueman]

RE: Re: RE: where to buy nylon line?

Thankds for the pic...thats the way I am installing them but not the way they came apart...somebody did it wrong. I didn't twist the can...it just seems that the entire can won't 'seat' fully? once the bolt is tightened down the can can still move...I'll figure it out tomorrow. Thanks cranetruck
Doc

 

[houdel]

The two different types of fittings shown here are used on the multifuel engines I have here to look at. What are the pros and cons? Is a special tool needed to install the top one?

BTW, if you look closely at the compression line (the lower fitting), you can see that the tubing is depressed on either side of the compression ring. This is caused by compression ring compressing the tubing.

One of Connie's tips was to use a brass ferrule INSIDE the tubing to take up come of the compression force and clamp the tubing tightly between the ferrule and ring instead of simply deforming the tubing. Over tightening the tubing will allow it to leak. The more you tighten the compression nut to stop the leak, the more the tubing is deformed and the tubing leaks more! It is kind of a paradox, the tubing starts to leak, you tighten the nut to try to stop the leak, but instead the leak gets worse!

 

[rdixiemiller]

RE: Re: Fuel line fittings

There are several grades of nylon tubing available. The Nylon 11 had good chemical resistance. Some are more flexible, and run at lower pressures. Look at the McMaster Carr catalog online. It has charts showing the chemical resistances of various materials, plus pressure ratings. Water service tubing you get at home improvement stores is often polyethylene, and won't stand hydrocarbon solvents.

 

[rdixiemiller]

RE: Re: Fuel line fittings

There are several grades of nylon tubing available. The Nylon 11 had good chemical resistance. Some are more flexible, and run at lower pressures. Look at the McMaster Carr catalog online. It has charts showing the chemical resistances of various materials, plus pressure ratings. Water service tubing you get at home improvement stores is often polyethylene, and won't stand hydrocarbon solvents.