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Fuel Lines. AIR-TECH

Fuel Lines

This month’s article is not politically correct, reader be warned.  

In the hot ass town of Redding, Taxafornia (Did I say that?), I see more engine fires caused by American fuel line than any other reason. Why’s that? first of all, it’s the wrong size. German hose is 5mm or 7mm. American fuel line is ¼ or 5/16. Granted, it’s easy to put on. So I see guys put it on and crank down a hose clamp. Does that work? Kind of, but let it get hot then see if you can pull in off. More than likely, you can with ease. Secondly, if you look at the german line it has a braided cloth on the outside. American line has a braid but it's in the middle of the hose. “So what?” you ask. When rubber gets hot, it expands. If the braid is on the outside and the rubber expands what direction does it expand. Inward is the answer. On the American hose it expands outward. Not so good. When you go to pull off American line it comes off easy  because it’s the wrong size to begin with and because it doesn’t have that braid on the outside. German line is a pain to get off. Most of the time you have to cut it off. Why’s that? Ever played with chinese finger cuffs when you were a kid? That braid when you pull on it gets tighter. So if your going to remove the hose for any reason first try and spin it then using a screwdriver try and push the hose off instead of pulling.

Installing german hose is not the easiest. If you do it dry you will fight it. The trick here is put a drop of oil in the end of the hose. It will slide right on. Those of you who run IDF carbs have a problem in that the carbs take 7mm line and the fuel pump and metal line is 5mm. Don’t just tighten the hose clamp on the smaller fitting with the big line. I use the plastic fuel filters that have a step on them.

 From the pump I use 5mm line and push it onto the first step of the filter. Then I use the 7mm line on the out of the filter and push it up to the second step. I run my 7mm line from the filter to the backside of the fan shroud on the drivers side to the “T”, then a short line to the drivers side carb and a long line on the passenger side. If you are running dual carbs you do not have to have equal length fuel line to each carb. The carb needle and seats work independently of each other so they don’t care. When the system is dry (first time starting) yes the driver's side gets fuel first. This doesn’t really matter because once the system is wet the needle and seat determines when to let fuel in. It doesn’t care what the other carb is doing.

Now let’s talk about fuel. Those of you who are my age or older will remember the days when gas was red. Yeah, the good ole days. Now we have fuel that looks like piss and we pay a lot more for it. The problem is the ethanol in it. That in itself is not a huge issue, but the problem is if the lines dry out from not driving or running the motor the ethanol will start eating anything that’s rubber. Think about that. Fuel pumps have a rubber diaphragms, carbs have a rubber diaphragm for the accelerator pump, and of course the fuel line. I have seen fuel lines looking more like drip irrigation after sitting dry. Not good on a hot motor.

Some American fuel lines are made with a rubber that the alcohol won't eat. That’s fine and dandy, but the fuel line is still the wrong size. So now what? If I know the car is going to sit, I mix marvel mystery oil in my gas. The longer it’s going to sit the more I pour in. If I know the motor is going to sit over a year then I run straight marvel until the motor starts smoking from it. Then in ten years I can put fresh gas in it, start it, and kill millions of mosquitos from the smoke until it clears up and all my rubber parts are still good, even the fuel lines.

At the time of this writing this article I am doing an experiment with a new hose. We had been using the brand Continental. Yes it fits, but it does get eaten by ethanol. Please keep in mind only when it drys out does the gas eat the rubber. If it stays wet then no problems. So back to the experiment. I found a german manufacturer that has the correct size braided hose, both 7mm and 5mm, that they say won’t get eaten by etholone. Its cost twice as much as the Continental brand, but if I only have to buy it once and it’s safter I don’t care.  I don’t have the results yet so I can’t say either way. The only way to test it is soak it in piss, I mean gas, then let it dry out for awhile and see if we still get drip irrigation. I should have some results in the coming months and if it does work then I will be switching to it and only carrying that brand.

So there you have it. By the way, most carb kits come with American style fuel line. I usually give it to my V8 friends or throw it in the neighbors yard. That guy really need to clean his yard.

Published on Wednesday, February 27, 2019 in Air Tech Articles, Tech-Tips. Comments: 2


  • Posted by Rickey Coder on Monday, June 03, 2019

    Ok, so have you decided whether this new fuel line is the right stuff to depend on or not? In my 1969 Transporter I am using an American fluid line that is rated at 3000 psi burst pressure, has about four layers of material including on of stainless wire and one of teflon and an inside layer of butyl rubber and likewise one on the inside...I also put abut half a pint of Marvel Mystery oil to five gallons of premium fuel every time I fill up my BUS. I know this is probably overkill but as yet I have had no leaks or other issues, as well as a happy valve train with no smoke out the headers. I have had this fuel line on going on three years since I was living in "Taxafornia" as you say and now living in Arlington, Texas. Thanks for the info.

  • Posted by Wolfgang Staff on Monday, June 03, 2019

    Rick sounds like you have hydraulic line which is damn good hose. Not cheap either. My concern would be the correct size. If you found some that is a tight fit then it doesn't get any better then that. Marvel Mystery oil is such a great product. I use it a lot around here.
    Thanks for the comment.


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