Lotus Elan

fuel hose deterioration

PostPost by: bob_rich » Tue Jun 11, 2019 5:38 pm

HI Folks

Gave the +2 it annual service to day and am getting a bit concerned about the state of the hoses use for the fuel injection ( car has a Emerald system wasted spark, with jenny throttle bodies and ford 36 tooth trigger wheel). The hoses are only around 4 years old. I have attached a picture of a section of hose that is in good order with a clear description of what its spec is. The OD of the hose is 14.5mm. I have looked for a similar hose on the web and I found one with a part number incorporating R7 rather than R10. Anyone know what this means? Could this cracking be related the use of modern fuel with added bio fuel ( usually fill up with 97 grade at local BP garage.)

I have attached a picture of the cracking. from what I can tell the bend radius of the hose seems with spec and I used springs to keep it in place and contain it so it does not put any stress of the fuel rail fittings.

Any opinions or advice would be helpful


hose-cracking1.png and
p6110539.jpg and
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PostPost by: Grizzly » Tue Jun 11, 2019 5:51 pm

Not seen one as bad as that but there is allot of rubbish no make hose about at the moment, i'd suggest only using quality fuel hose (Gates is my go to make) after all you don't want fuel spraying all over the place.
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PostPost by: mbell » Tue Jun 11, 2019 6:04 pm

The R7 v R10 is difference is the fuel types that the hose is rated to handle. You should carefully consider/research it when purchasing replacement hose. I suspect UK Super probably has something like 5-10% ethanol, so you need a hose capable of handling that, with fuel hose generally better safe than sorry. So over spec and buy good quality hose as suggested.
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PostPost by: pharriso » Tue Jun 11, 2019 8:20 pm

From http://www.underhoodservice.com/correct-fuel-hose-installation/ :

The Society of Automotive Engineers (SAE) is an industry group that creates standards for the automotive industry. When it develops a standard, it applies to all manufacturers in hopes of reducing engineering and testing costs.

SAE has more than 16 active and inactive J30 standards for fuel and oil hoses. If you look at the side of a fuel, oil or emissions hose you will see the letters ?SAE? followed by the number 30 (some will have a J first). Next in the sequence will be the letter ?R? followed by a number. The number after the ?R? refers to the section of the performance standard it pertains to. The criteria are typically permeation, chemical resistance, construction, temperature range and kink resistance. The higher the standards go, the more criteria that must be met.

?R? numbers in some cases do not determine the pressure rating for the hose. Hose manufacturers typically print on the hose if it is intended for use on fuel injection systems. Also, you should check with the manufacturer of the hose to see if it is compatible with fuels like E85 or biodiesel. NOTE: IF A HOSE DOESN?T HAVE A SAE J30- STANDARD ON THE SIDE, DON?T INSTALL IT IN A FUEL SYSTEM.

SAE 30R6 hoses are designed for low-pressure applications like carburetors. These can also be used as an emissions hose.

SAE 30R7 hoses are designed for fuel. These can go under the hood and are typically used for low-pressure applications.

SAE 30R9 hoses are designed for high-pressure applications like fuel injection and oil. These are designed to stand up to the environment under the hood.

SAE 30R10 includes hoses that are submerged in fuel. This type of hose is used inside the fuel tank and typically on the fuel pump module. This type of hose uses a special layer on the inside and outside to prevent the core layers from being saturated in fuel. But, don?t use it under the hood. R10 hoses can?t stand the heat.

SAE J30R12 includes low-permeation fuel feed and return hoses.

SAE J30R14T1 is the standard for ultra-low permeation properties. This type of hose is typically approved for use with leaded and unleaded gasoline, diesel, biodiesel, E85, methanol, ethanol and gasohol fuels. These are typically used for low-pressure applications.
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PostPost by: elanman999 » Tue Jun 11, 2019 8:49 pm

That's not very good if it's for injection pressures.
After a quick search I cannot find R10 but found some R9 here:- https://www.advancedfluidsolutions.co.u ... e-95-c.asp

I had a similar problem when I went to EFI. I did find some OEM quality tubing but the suppliers had large (1000m) minimum orders so ended up using braided PTFE tube. Far from the cheapest and not the most convinient to install (large bend radius) but is a nice secure job. See here:- https://www.ebay.co.uk/str/torquesuk
For running through the cockpit I used copper/nickel tube on one of my cars.
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PostPost by: bob_rich » Sat Jun 15, 2019 7:25 pm

Hi All

Thanks for the useful info and the explanation of the R numbers. I obtained and fitted some R9 hose from Advanced Fluid Solutions which it transpired was located just down the road from where I live and so I could have saved the postage! I will keep a careful eye on this hose to see how it works out. The new hose had the full SAE code on it together in an embossed date code of 2019 01.

There is still some of the older R7 hose on the rear of the car around the fuel tank and pump but being in the boot the environment is not as severe and so this seems to be surviving OK.

thanks for all the help

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PostPost by: Higs » Sat Jun 27, 2020 2:22 pm


On the subject of fuel hoses, here is a salutary tale.

In Jun 2014, I bought a new shiny braided fuel line for the webers on my Plus 2 from one of the usual supects here in the UK (from the look of the various kits, they all seem to use the same supplier). The restoration has taken forever and is still ongoing. I briefly started the engine 18 months ago for about 5 or 10 mins maximum. Apart from that (and about a month afterwards), the hose has been free from fuel.

Following further restoration work (engine out / in etc.), I tried to start the engine this week but when I put some petrol in the car, it flowed freely out of the braided hose nearest the pump. It was not leaking from the olive but from the hose. Luckily the ignition was not on and there were no sparks or the Elan would have been toast.

I removed the stainless hose, confirmed there was a leak and decided to cut it all open to investigate. My findings were:

1 The braiding and fittings looked perfect and shiny.
2 Inside the braiding there is a cotton wrapped fuel line made by Cohpro (Cohline 2122) which meets Din 73379-B (which, I believe is eqivalent to SAE 30R6 above).
3 Under the cotton braid, the leaking hose was very badly perished.

Two photos to look at:

IMG_3207.jpg and
The nice shiny brading and two of the hosed looking good in their cotton brade

IMG_3208.jpg and
The perished hose

What lessons do I take from this?

1 R6 line does not like modern fuels
2 Lines need to be R9 or R14 (both of which are compatible with modern fuels)
3 Covering it all in stainless braid looks good but covers up what could be a serious problem
4 I will use bare R9/R14 with clips from now on - not as pretty but I can inspect the hose condition and replace as required.

Hope this is useful.

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PostPost by: Andy8421 » Sat Jun 27, 2020 4:48 pm


I purchased a similar shiny braded fuel hose from one of the usual suspects (can't remember which), the type with the pre-fitted banjo ends, two into one fitting and pipe to fit the fuel pump. Starting the car this year (pipe was about 8 years old), fuel sprayed out of three separate pinholes in the pipe, through the braid and over the engine. I didn't bother with the post mortem, but put it straight in the bin.

I had assumed I had a dud, but perhaps the problem is more common.

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PostPost by: Geoffers71 » Wed Jul 08, 2020 10:01 am

My S2 is also fitted with the shiny braided fuel lines and the tale above has moved me to replace them with a more ethanol resistant pipe. Here I have a dilemma. My Scimitar GTE is fitted with J30 R9 rubber fuel line and this is showing cracks as shown above, so this suggests that even R9 is not that safe. I have ordered some Cohline, which is in excess of R10 (it says !!). I’m still wary. I do have some braid covered PTFE (Teflon plastic) pipe which I could use instead and might be safer. What would you do?
Any informed suggestions welcome.
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PostPost by: Emma-Knight » Wed Jul 08, 2020 1:19 pm

We used „Well-Tube“ for a medium pressure fuel Injektion testbed. Average was 50bar pressure with normal e5 or 10 gasoline. We had high restricrions due to ex-safety. Well-Tube is some kind of steelbraided pt-something which has spiral rims and so is more flexible than ptfe pipe.
I was thinking about havin the normal steel braided harness rebuilt with that Tube. By our local Hydraulik (Truck and Machine) Supplier. The outward appearance is like normal steelbraided rubber Tube
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PostPost by: HCA » Wed Jul 08, 2020 3:21 pm

Wow! In this day and age with injection, I really am surprised anyone is using rubber hose.

On my Audi, I put my trust in VAG to spec the correct hose for their 440+bhp cars. I happen to know it is teflon though.. 8)

But for rebuild classic cars for as long as I have been injecting them, I would not contemplate anything but braided teflon hose with JIC fittings - and then I would only trust Speedflow as a supplier.

A correctly tuned injection system on a sub 200bhp engine is pushing 40-50psi around the place. I really would not want to be using a rubber hose showing signs of cracking...
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