Lotus Elan

Easy fuel breather mod

PostPost by: Donels » Fri Aug 03, 2018 6:10 pm

I’ve been thinking modifying the filler neck for the breather mod for a while but not seen a solution that meets my needs. I don’t want to weld a boss on the filler neck as I’ve plated it already, want it suitable to fit after the filler neck is installed and I don’t have access to a lathe. I’ve come up with a simple solution that may be useful to others.

* Starting point is a 8mm straight domestic plumbing brass coupling, but a 12mm or 15mm could be used.
* Cut the olive retainer off one of the unions, effectively turning the union into a brass nut.
* File the non-olive end of the 'nut' to suit the curve of the inner surface of the filler neck. Mark two opposite faces so you know which you’re filling, holding the nut and neck to the light to assess the fit. With care you can get an tight fit.
* Round off the ‘cut’ end of the nut.
* Drill the neck to an appropriate size so the coupling body is a snug fit. Too big and it will be difficult to seal. Make sure the hole is only finger depth down the neck as you need finger access to assemble it.
* Fit the coupling body through the hole, slide the nut down the neck and tighten the coupling pulling the nut tight against the neck inner surface, making sure the nut is correctly aligned.
* For final assembly apply a suitable sealant or PTFE tape to get a fuel tight seal.
* Make an appropriate tail for the non-modified Union end and connect to breather pipe work.

Hopefully the following photo’s explain. I’ve used 8mm but maybe 12mm would be better. I’ll see and modify accordingly.
8243fabc-0cc9-49bb-b70f-f8854e81b246.jpeg and
f1648cfd-22d5-4dd0-8a7e-28ec4470053d.jpeg and
c3e442cb-67dd-4533-96d7-9ad98b741c5a.jpeg and
0fbfc613-469c-41d4-844b-a8481e2b7ec5.jpeg and
76c45d9d-33e0-4bb1-9ae5-35150b233b01.jpeg and
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PostPost by: Chrispy » Fri Aug 03, 2018 10:17 pm

I did something similar. Drilled and tapped the filler tube, screwed on the fitting and then put a bulkhead nut on the fuel side. Been working well for 6 months.

Still have terrible problems with fuel coming out of the cap when more than half full and driving around corners :(
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PostPost by: john.p.clegg » Sat Aug 04, 2018 4:56 am

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PostPost by: JonB » Sat Aug 04, 2018 8:21 am

Late 1972 Elan Plus 2S 130/5 - UK - Unit 50/1115L
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PostPost by: alan.barker » Sat Aug 04, 2018 11:12 am

bonjour Jonb,
have you tried to fit it in your car as "dougal9887" suggested.
I have used this mod, that is the non-return valve new + reducers in my TVR 3000M and TVR 3000S with a great success. To make it easier to slide into position i used wd40. Plus don't forget the jubilee clip on the outside.
Alan
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PostPost by: JonB » Sat Aug 04, 2018 8:51 pm

Bonjour Alan

Gizza link!

And PS, I note your profile no longer says "Sussex". What's going on?

:)
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PostPost by: alan.barker » Sun Aug 05, 2018 5:13 am

Hi Jon,
maybe you're getting mixed with another Alan i've lived in France for 26 years now.
I looked at the link you gave and reread all of it and dougal9887 seems to explain it very well.
I hope you can get the mod to work on your +2s before the paint gets damaged by the fuel.
Alan
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PostPost by: Chrispy » Sun Aug 05, 2018 5:45 am

Thanks for the links. I have to do something soon. I've just been keeping the fuel tank under half which controls most of it and immediately cleaning any spilt fuel off the paint which has sealant on it. So far no damage or discoloration.
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PostPost by: JonB » Mon Aug 06, 2018 7:41 am

alan.barker wrote:Hi Jon,
maybe you're getting mixed with another Alan i've lived in France for 26 years now.
I looked at the link you gave and reread all of it and dougal9887 seems to explain it very well.
I hope you can get the mod to work on your +2s before the paint gets damaged by the fuel.
Alan


I'm not filling the tank these days - £10 at a time. Haven't put the external clip on yet, but it is pretty tight in there.

You're right, I got you confused with SpyderFan. Soz... :)
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PostPost by: vxah » Tue Aug 07, 2018 12:55 pm

Or, find a piece of steel tube that fits nicely inside your original filler neck and bond it in with epoxy (I used tank sealer as I know that is fuel proof) that will give enough thickness to drill and tap the filler neck for a tapered thread vent spigot fitted after the neck goes in the body.
I had fitted a Focus type sealing flap just inside the top of the neck so I could not use any heat..The inner pipe keeps the flap in place as well!
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PostPost by: davidc » Tue Aug 07, 2018 3:26 pm

Am I correct in thinking the fuel breather mods are not the reason for fuel leakage on hard cornering?

i.e if I don't do the mod could I still have this problem, or in other words if I do do this mod could I get this problem?

whilst tinkering in garage I've had the breather pipes clamped over which is great at stopping garage stinking of fuel but clearly not a long term solution.

I have clamped 2 ramair oil breather filters to end of each tube but it occurred to me it might not be wise to have 2 bits of foam soaked in petrol vapour hanging below the car so might look for plan B!

is the leakage to do with the petrol cap seal?
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PostPost by: alan.barker » Tue Aug 07, 2018 4:40 pm

Hi David,
1. the Breather mod is to stop your car stinking of Petrol when you leave it in your Garage. DO NOT block both Breathers because Fuel in the Tanks needs to breath. If you block both Breathers the Fuel will expand in the Tank and come out of the Filler.
2. the MX5 non return in the Filler Neck is to stop Fuel coming out past the Filler Cap when taking corners.

You need to do both mods
I hope this helps
Alan
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PostPost by: Bigbaldybloke » Fri Aug 17, 2018 10:25 pm

These special valves should cure your fumes problem, they let air into the tank with no restriction so that as you use fuel it doesn’t pull a vacuum in the tank. They also act as a pressure relief valve so that if the car gets hot in the sun and the fuel expands they open to relieve the pressure, but are normally closed so fumes cannot escape. I have fitted them in the breather from each side of the tank and routed the pipes up the rear pillar then down into the rear wheel arch, the pipes no longer pass over the roof behind the head lining. I also have a vent to the filler neck which copes with refuelling venting.
Attachments
8b1632ae-3073-4b79-992a-1ac019d556a2.jpeg and
Vent lines around tank
05f04f1e-b311-4ffc-bb70-9538feef6792.jpeg and
Valves fitted in pillar
8c6336a9-71cd-43f5-9960-207e476e6ac7.jpeg and
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PostPost by: david.g.chapman » Thu Aug 23, 2018 6:01 pm

I take it that these are the ones shown:

https://www.newton-equipment.com/tank-v ... alves.html

It looks like an elegant solution, and you can simply install them in the existing breather pipe runs on an unmodified vehicle?

How does it affect filling the tank if the valves stay shut as the internal tank pressure rises, or do they pop open under those conditions?

I can't see a price on the web-site - can you tell us how much they are?

Dave Chapman.
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PostPost by: wotsisname » Fri Aug 24, 2018 9:03 am

I am guessing that these are the same at ~ £43

https://www.carbuildersolutions.com/uk/ ... urn-valves
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