42 replies to this topic

[Steve-O 2014]

I have noticed that under the Mini that we have purchased has rubber pipe from the tank which then goes to copper pipe that measures 6.5mm external diameter pushed into it and clamped onto it.

 

The wall of the copper pipe will be about 1mm per a side so internal diameter will be about 4.5mm (or maybe smaller if they have crushed it with the clips clamping the rubber hose to it)

 

What should the internal diameter of the fuel line be? Should it be 8mm??

 

Thanks

 

 

[crf150]

Would it be 8mm ? As i think i have some 8mm copper pipe at work which i could use, and some sleeving so that the copper pipe has extra protection

[Steve-O 2014]

The ID of the copper pipe is 3.5mm as I measured the copper pipe he used for the fuel overflow pipe

[Mini 360]

My fuel pipe was 6mm OD I believe.  

[Steve-O 2014]

did you mean 6mm ID ??

[coopdog]

6mm Id as standard I believe

[dklawson]

Steve-O, why did you jump from the dimensions you measured to assuming the fuel hose should have an inside diameter of 8mm? Everything you measured and estimated sound "correct" to me.

 

I can only comment on the early cars.  Metric does not apply.  The OD of the metal tubing would be 1/4" which is close to the 6.5mm mentioned above.  The ID of 3.5mm mentioned above sounds low, I would expect it to be closer to 3/16"  (somewhere between 4.5mm and 5mm).

 

The tubing should not be copper.  Fuel line is supposed to be steel as copper is subject to fatigue failure. 

[Steve-O 2014]

could 6mm ID rubber hose be ran all the way from the rear to the front?

[Steve-O 2014]

I measured the OD of the copper fuel line that has been used and its 6.5mm OD

I measured the ID of the copper fuel line used and its 3.5mm ID

 

The rubber hose ID is 6.35mm

 

The OD the fuel inlet on the carb is 6mm

The ID of the fuel inlet on the carb is 4.6mm

 

So im guessing as long as the ID of the fuel line is at 5mm is should be fine since the carb is 4.6mm ID ?

[Steve-O 2014]

I did that because after googling I saw that people were using 8mm Microbore from B&Q

 

 

Steve-O, why did you jump from the dimensions you measured to assuming the fuel hose should have an inside diameter of 8mm?

[Mini 360]

did you mean 6mm ID ??

I did indeed!  Why are the I and O keys next to each other on the keyboard?

[tiger99]

 

 

did you mean 6mm ID ??

I did indeed!  Why are the I and O keys next to each other on the keyboard?

 

So that you and I will keep making the same mistakes!

 

But in answer to an earlier question, you can use proper "rubber" fuel hose, with the appropriate legally required markings, for the entire run, but it is not advisable. It must on no account be run inside the car, as the rubber is not entirely impervious to petrol vapour, and there will be a continuous smell of fuel if you use it inside. That is dangerous, because as well as being unpleasant it will mask any fresh smell due to a leak.

 

You can also get braided fuel hose, PTFE with stainless overbraid just like brake lines, but not rated at such a high pressure. PTFE (Teflon) should be immune to the effects of E10, or even E100 fuel. Braided is not ideal either, because how do you neatly fix a flexible pipe? Rigid pipe really is better. See here, and I suggest not using ali, as stainless has far better fatigue properties:

 

http://www.demon-twe...hardline-tubing

 

 

[crf150]

Steve-O, why did you jump from the dimensions you measured to assuming the fuel hose should have an inside diameter of 8mm? Everything you measured and estimated sound "correct" to me.
 
I can only comment on the early cars.  Metric does not apply.  The OD of the metal tubing would be 1/4" which is close to the 6.5mm mentioned above.  The ID of 3.5mm mentioned above sounds low, I would expect it to be closer to 3/16"  (somewhere between 4.5mm and 5mm).
 
The tubing should not be copper.  Fuel line is supposed to be steel as copper is subject to fatigue failure.

So your saying that I shouldn't run copper pipe from the tank to the mechanical fuel pump? I was thinking of running copper pipe from where and to I said and running it inside a clear rubber type sleeve to protect the copper. Would this be fine ?

[dklawson]

Check with Tiger and see what he says.  I believe on a number of occasions he has commented about not using copper for brake and fuel lines.  He often knows the specific U.K. regulations that apply.  I can only say that in the U.S. copper fuel line is not used.

[tiger99]

Yes, copper will react with E10 fuel, and cause lots of problems downstream, but from the point of view of the fairly low pressure in the fuel system should be safe. It does need to be anchored down tight, as it is subject to fatigue fracture if it is allowed to vibrate.

 

In brake systems, copper as such is just plain unsafe, as it will not withstand sufficient number of full pressure brake applications without fatigue failure, even if the vibration aspect has been dealt with. Kunifer (copper/nickel alloy) is the stuff to use, and can be recognised as it is a lot harder that copper when it comes to bending or flaring, and has a reddish-grey tinge, copper being red.

 

Copper is illegal in exhaust systems, and although it is possible that it is not mentioned in the current version of the Construction & Use Regs (no need now, no-one uses it, why would they want to?), the problem was that it tended to react with certain combustion products to form explosive compounds, or so it was said. I think it was banned in about 1920. It also suffers badly from localised corrosion pitting due to chloride ions (as in salt!), especially when stressed, not what you would want in either a brake or fuel system.