Lotus Elan

SOLUTIONS: Petrol smell in boot and in car

PostPost by: gavk » Thu Oct 04, 2018 9:34 am

Good morning,

Just wanted to update everyone on my recent findings when trying to cure petrol smells in my +2.

I assume it is a very common problem (at least in the boot) but would be interested to hear from anyone who has a fresh smelling boot!

Research on various forums has led me to the conclusion that many old rubber hoses display high levels of permeation (fuel vapours pass through the rubber without any visible signs of leaks). This situation has been worsened by changing composition of modern unleaded petrol.

The attached screenshot is from the (old) SAE J30 specification for fuel hoses and shows the allowable Permeation of a new fuel hose for various specs, R6, R9 etc.

screenshot-2018-10-04-at-09.54.46.png and

As you can see a R9 hose will allow only 15 g/m2/day versus 600 g/m2/day for a R6.

Assuming your boot was full of R6 hoses you could cut the fuel smells to 1/40th by switching to R9, thats not even taking account of the degredation in performance of older hoses.

In the last year I have replaced and upgraded the following hoses with BioFuel rated hoses (supposedly even better than R9):

Engine breather hoses
Oil Catch can hoses
Fuel tank breather hoses

I have also replaced:
Fuel Filler Elbow
Fitted new Newton inline breather vent valve
Replaced fuel filler cap gasket

This has now doubt made a huge improvement but I was looking for perfection. The cockpit is a lot less smelly but the inside of my boot still smells.

I have an instrument at work which detects vapours and gives a readout in ppm (parts per million) or ppb (parts per billion), so I decided to use it to identify the source of the smells in the boot.

The zerod the instrument in the car park
Background level in boot was less than 1ppm
When i placed the instrument near my new breather hoses there was a small rise but not huge.....good news, they were working well.

BUT my fuel filler elbow and braided fuel injection supply and return hoses were all showing very high levels of permeation, the instrument showed levels of up to 100ppm when placed near to any of these hoses! The braided fuel injection hoses were approximately 6 years old, the fuel filler elbow only 1 year old and was supposedly high spec from a small rubber supplier I contacted.

In an ideal world I would replace all of these hoses with a higher specification but I think the biggest gain can be made from replacing the fuel filler elbow.

Not only is the filler elbow subjected to fuel vapours, it also has fuel sat in it and it has by far the largest surface area of all the hoses which means it is probably the worst culprit.


Everyone looks to their breather pipes to fix fuel smells which is a good idea, especially if you still have them running through your headining. But I would suggest the filler elbow would also be a very good place to start.

I would like to replace the 57mm fuel filler elbow with either a high spec rubber (R9/Marine A1/ Biofuel grade) hose or a metal elbow. The prblem with a metal elbow being that rubber joiners are still required.

High spec rubber would be my preference for ease of fitment but Im struggling to find such an item available, I dont believe any of the filler elbows commercially available are low permeation when subjected to fuel constantly sitting inside them.

Sorry I havent provided a complete solution but I hope this thread will be of use to some of you trying to make similar improvements?

Perhaps if there was enough interest we could find a rubber supplier who would make a high spec filler hose?


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PostPost by: awatkins » Fri Oct 05, 2018 3:34 am

HI Gavin ? one thing I learned the hard way working on a GT40 is that if a petrol leak is small enough it can cause the same effect but be very difficult to find, the reason being that surface tension in gasoline is extremely low so the fluid from the leak is close to invisible. So if there is any way you can pressure test the remaining old hose(s) that might lead you to a culprit that is, strictly speaking, not permeation. Of course in a way it?s amoot point inthat even if that is what?s happening replacing the hose or elbow will fix it regardless. I guess my point is you could go ahead and replace the remaining old parts with new ones of the same permeability and discover the problem is largely or completely gone.
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PostPost by: vxah » Fri Oct 05, 2018 7:27 am

Good work there Gav! My +2 has a bit of a fuel smell in the boot that I would love to eliminate! I have a few extra hoses in there for the electric pump and modified vent hoses but these are all hi spec GM hose, I do however have a new filler elbow fitted and as I recall there is not much choice when it comes to supplier for these? Maybe I should start looking for something mainstream to replace it with? Having said that I think I did look at the time of rebuild but failed to find anything of that diameter.
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PostPost by: gavk » Fri Oct 05, 2018 8:31 am

Thanks for the replys.

Awatkins, I totally understand where you are coming from however the voc detection equipment I used is extremely sensitive and was indicating high levels along the length of every braided hose (4 or 5 of them) and along the length of the elbow.

While I can't rule out a very small leak from any of the ends of these hoses, or a small leak along the lengths.....what I can say is it is highly unlikely (from the readings I saw) that all the hoses have leaks along their lengths.

Permeability is the main factor here. As mentioned the elbow is a very high quality rubber and it is also has very thick walls and was only replaced in last 12months, it is in a location away from abrasion so I can rule out leaks along its length.

Given the surface area of the filler hose I think a low permeability elbow is the priority for anyone (once breathers upgraded and leaks eliminated).

Vxah, something from OEM market is a great idea but I assume there would be alot of work to find something that fits. I can't believe the aftermarket doesn't have it! I did look at the petrol resistant flouro lined silicone hoses but even they are not designed to have petrol sitting inside them continuously.

I have found the following metal elbow on eBay
https://rover.ebay.com/rover/0/0/0?mpre ... 0897188730

My main concern is that my tank outlet is not aligned perfectly with the filler so a straight elbow may not work
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PostPost by: The Veg » Fri Oct 05, 2018 10:21 am

I?ve got a reinforced silicone elbow on mine. Will be interesting to see how it does once the car is ready to be fueled.
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PostPost by: gavk » Fri Oct 05, 2018 10:37 am

Veg, I looked into flouro lined silicone before I bought my current elbow and remember being told that even samco profuel was not suitable for constant contact with petrol, that is why I didn't go for it before.

However, since just seeing your reply I have looked on the samco website again and see they suggest it is suitable for constant petrol contact! Could be a great solution for some on this site, unfortunately the leg lengths are not suitable for my use but I could maybe use a combination of metal elbow with samco profuel joiners.....worth considering.
screenshot_20181005-1130392.png and
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PostPost by: wotsisname » Fri Oct 05, 2018 1:25 pm

Sorry, more questions than answers....
Can you buy a thin wall PTFE tube of the right sort of diameter and length ? It might be possible to fit this inside and use the hose clamps to hold it in place... I appreciate that fitting isn't going to be easy as the rubber hoses usually require a degree of twisting and forcing to get in place. this if similarly pre-lined tube does not exist
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PostPost by: billwill » Fri Oct 05, 2018 6:24 pm

Back around 2001, a firm in Finchley doing body repairs for me also fitted an electric fuel pump in the boot and used a braid-covered flexible pipe to get the fuel from the boot to the engine compartment. They routed this in the cavity under the door on the right-hand side.

This gave rise to a strong smell of petrol in the cabin, but with no apparent leaks. It was very annoying.

It persisted until I got really fed up with it and replaced the long run through the cabin using a Kunifer pipe. I had to use small rubber (with braid) lengths at each end to connect it up, but I think it is fine. I think I obtained alcohol resistant 'rubber' but I will need to check it periodically.
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PostPost by: Bigbaldybloke » Sat Oct 06, 2018 4:55 pm

I?ve recently bought and fitted a replacement alloy tank, as my steel one was badly corroded. Pity they don?t make one with an extended alloy filler neck that turns up to the filler cap hence only need a short straight flexible connector. That would do away with the elbow submerged in petrol the whole time.
Other option would be more drastic, redesign the tank and body to have the filler nearer the centre of the car with the filler straight down into the tank. Would help eliminate all the breather pipes over the roof too!
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PostPost by: stugilmour » Fri Oct 26, 2018 12:01 am

This is what I used for the fuel filler elbow. Sourced it from a Canadian industrial supply, but sure it is commonly available in the US as well. Not sure if there is a perm spec associated with the SAE J30R6 they quote.

I think this is the actual part I used. I am sure the elbow legs are not 8 feet long! Trimmed to length and clamped in place.

Continental Contitech
Fuel Fill Hose
59208 - 2 1/4? ID 2 5/8? OD
90 degree 8? leg length

816401d7-fc13-4e92-80c1-921fbf3700b6.png and
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