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What diameter is my fuel hose?

TR7th Heaven

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I have a 1970 Vitesse MKII.
I want to replace the fuel hoses that run between the Stromberg carbs and also the run off from the right hand carb.
Are they 1/4 inch diameter?
If so, I assume that 6mm will be adequate? (6mm is very slightly less than 1/4 inch)
I've looked on various suppliers' sites but can't see the exact size.
Thanks in anticipation,
Rich  ;)

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I bought some 6mm hose off ebay. Seemed the cheapest place. Fits well in place of all the perished hoses. I also bought a fuel tap, which I have fitted coming off the fuel tank, good for isolating the tank, rather than pulling hoses off.

The long length of fuel line that runs under the car upto the fuel pump isn't rubber and a thin looking plastic line. Anyone know what this is called and why it's used instead of rubber line?? The pipes going into my carbs(from the metal pipe), again looks the same thin stuff that runs under the car. Whilst the 6mm rubber is thiicker, I'm going to replace the thin stuff with this.

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6mm should be fine, though on one car I had it felt a little big, and I ended up with some 5mm stuff.

Re hose quality have a look at this, stolen from another forum

Fuel pipe research (long!) - for discussion!

You may recall that I had a rant about rotting flexible fuel pipe a while ago (LINKY).

In the end I did a lot of internet research, and came up with the following observations:


* Since getting my car on the road 7 or 8 years ago I have had to replace rotted flexible fuel hoses 3 times. Each time the hose has cracked and was dripping fuel everywhere.
* I have always used decent quality hose (Gates, or similar).
* It seemed to happen randomly but especially after a long spell in the garage, whether due to bad weather or whatever. (significant point #1)
* Some other people had similar problems.
* More people were using similar hose and having no problems (significant point #2)

Results of research

* Petrol has changed significantly over past few years - it now contains more alcohol-based substances, which are very corrosive to normal rubber.
* Hoses in the USA are marked with an SAE code, e.g. SAE J30R9, according to its ability to resist modern fuels. As much of the hose bought in the UK is made (or sold) in the USA then these markings may appear here.
* There are 4 significant groups of SAE codes:
Unmarked hose - will probably be for the original petrol formula, without modern additives (but see later comments).
30R6 - This is the standard for the petrol formula of 5 - 10 years ago, for fuel injection. The bore may or may not be lined with Nitrile.
30R7 - This is the standard for the petrol formula of 2 or 3 years ago, for fuel injection. The bore is lined with Nitrile.
30R9 / 30R10 - This is the current standard. The bore is lined with Fluoroelastomer/Nitrile. 30R9 has Fluoroelastomer/Nitrile on the inside, while 30R10 has it inside and out, which allows it to be used immersed in petrol (e.g. in a fuel tank).
* There is also a marine grade for use in boats - ISO 7480 A1 - that is roughly equivalent to 30R7-and-a-bit, with added fire resistance.
* One of the causes of fuel pipe failure described in the USA literature is stale modern fuel, not so much the fuel itself. These fuels become extra-corrosive when they get old.
* The USA seem to use a higher percentage of alcohol in their regular fuel - but we're not far behind in Europe.

What got me angry...

* Gates in the USA only make and sell fuel pipe of grade 30R9 or better (they even have brand-new super-grades). Gates in the UK distribute unmarked hose to motor factors that, if you are lucky, is only 30R6. Why don't we get the same? Are they dumping their surplus stock on the UK?
* The Gates sales rep for the UK and Europe didn't know that the USA grades were far higher than his offerings - he didn't even know the trade names for the USA products (shown in every USA Gates catalogue).
* 30R9 is freely available on the USA ebay, at sensible prices, made by big-name manufacturers such as Gates and Goodyear. It is never (or maybe rarely) available on the UK ebay. Only the excessive postage stopped me from buying it there.
* One on-line supplier (Think Auto) advertised that their hose is 30R9, but when it turned up it was unmarked. I recognised that it was stuff that I'd used previously and told them so. To their credit they apologised, refunded my money AND paid for the return postage.
* There is a general ignorance about this whole issue - when I asked for a specific grade of hose many suppliers didn't comprehend, while others were almost abusive ("Our stuff is good enough...!).
* The one who did supply the correct hose, Hose World, advertised it as 30R10 on their website, the bloke on the phone didn't think it was any special grade when I asked, and when it turned up it was 30R9, which is what I was after in the first place!
* If you search on any USA car forum about fuel pipe you will see that most people are fully aware of this issue, and the need to use modern hose. There seems to be a general ignorance in the UK.

Last thoughts and recommendations

It was almost certainly stale fuel that rotted my fuel pipe(s).

1. Don't buy general-purpose hose from a motor factor, unless it has at least 30R9 printed on it. Even stuff off the Gates stand isn't good enough.
2. If you are getting it via the internet or mail order, don't be fobbed off by excuses. Only the proper stuff is safe for long-term use.
3. If you are going to leave your car unused for a month or so, consider draining the petrol, especially if you are unsure of your fuel pipe grade.
4. If you really can't get 30R9, consider getting ISO 7480 - this is easily available from marine suppliers in the UK (but see point 3). All proper fuel pipe in this grade has to be marked, to meet regulations.

Additional thought

Re-reading some of the websites I found during this research reminded me of an important indication of fuel pipe decay - smell.

If you go into your garage and there is a stink of petrol, but you can't find a leak, then it is very likely that vapour is permeating through the fuel hose. If this is the case then it is a fair bet that the hose will fail sometime in the near future... maybe not immediately, but sometime.

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Cheers Clive

It has been bugging me for years that the fuel pipes on my cars don't last very long and when complaining to suppliers they they say that don't know of any problems. Just replaced the pipes again on my Spit. The pipe was the type that is covered in a weaved fabric material, and only found it when I noticed the fuel bowl was wet and the pipe was sodden, where fuel was seeping through the rubber. It's criminal that the wrong material is allowed to supplied in this country with the obvious associated dangers of fuel potentially spraying under a hot bonnet.


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Upon returning from my MOT with the Spitfire, I walked past it later in the day and noticed a smell of petrol. Upon looking under the bonnet I found the inlet pipe to the fuel pump had split (old pipe of indeterminate age). Bit of a pain as the front of the car was downhill and the tank contents were syphoning out of the split.

I changed this (and all the other bits of rubber fuel hose as they were looking similarly dodgy) for some new marked pipe that I had in stock, will have to check the spec.

Re fuel smells, the PI has always had a fuel smell in the boot - but the hoses all look ok, will look more closely regarding this vapour thing!

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hello all ive recently removed the body on my vitesse to discover someone has completley replaced the fuel lines with copper pipes all the way along the whole system apart from where it joins to the tank, is it worth keeping them as they are or may this cause problems? Or is it in fact a good upgrade?

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