Lotus Elan

Easy fuel breather mod

PostPost by: Bigbaldybloke » Fri Aug 24, 2018 11:30 am

Can’t find my receipt but from memory the two came to around £85 including postage. I’ve fitted them in conjunction with the mod to connect the breather to the filler neck. These valves act as a relief valve in one direction and are open in the other direction, so as installed they let air freely back into the tank to prevent a partial vacuum as fuel is used, and open on over pressure such as when the car is left in the sun and the fuel heats up and expands or when filling the tank. Although the main air venting on filling is in the new vent line back to the filler neck. As my car was completely stripped and I didn’t like the thought of trying to fix the breather lines to the roof before fitting the headlining so my vent pipes just run up inside the rear pillars to almost the top then bend back down and go out the original exit hole into the rear wheel arch and finish below the level of the fuel tank. I should say that the car is not back on the road yet, I’m about to fuel it for the first time in over 35 years. I’ve lots more photos of the vent pipe runs if anyone wants me to post them.
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PostPost by: alan.barker » Fri Aug 24, 2018 11:50 am

Have you done the other "MX5 non return" to stop Fuel coming out the Filler Cap on corners with a full Tank also
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PostPost by: Bigbaldybloke » Fri Aug 24, 2018 12:27 pm

No, not done that mod as I never had problems with fuel coming out the filler cap once I fitted a new rubber seal on the cap. If I get problems I’ll fit it later. Immediate problem is I have literally just put a couple of litres of fuel in the tank for the first time and it’s leaking on the tank connection. Grrrrr.
New alloy tank, new banjo bolt. New copper sealing washers and new copper fuel pipe with new copper olive on it. Tried tightening it a bit more, but it’s still just damp on the banjo. Have to drain it and see if i can see what’s causing it. :-(
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PostPost by: alan.barker » Fri Aug 24, 2018 1:56 pm

I've found for the Banjo it's better to use Fibre Washers. The Olive should be Brass not Copper.
I imagine the Fuel Cap is non locking (there are 2 seals). The Locking Caps leak the most.
The "MX5 non return" is very cheap and no risk of Fuel damaging the paint on the rear Wing.
If you have just had a Paint Job done you will be crying when the modern fuels destroy it :cry: :cry:

I had a 1973 +2S130 and the previous owner had never done the mod. The Lagoon Blue Paint on the rear Wing had been destroyed by Fuel leaks. It was a hell of a job to get it repaired.
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PostPost by: Barney » Fri Aug 24, 2018 3:31 pm

Somebody can correct me, but doesn't the use of Copper (or brass) and Aluminium set up a galvanic cell, instigating corrosion?
galvanic-table.jpg and
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PostPost by: Bigbaldybloke » Fri Aug 24, 2018 3:43 pm

I don’t think it will be corrosion yet as it’s only recently been assembled and hasn’t even been run yet, this is the first time its had fuel in it, but it’s a good point. The tank is aluminium, the banjo bolt is steel, the banjo is brass, the washers copper the pipe is copper and the olive is either brass or copper. So, if I put fibre washers in it should insulate the brass from the aluminium, steel to aluminium should be ok as is brass to copper.
My understanding is that you also need some sort of electrolyte for this type of corrosion, will petrol act as an electrolyte?
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PostPost by: alan.barker » Fri Aug 24, 2018 5:05 pm

The original spec/setup.
Just to be clear there is NO Copper at the Banjo. The Banjo is Brass, Banjo Nut Brass Olive Brass, Fibre Washers, Fuel Pipe Plastic and Banjo Bolt Steel.

Alan
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PostPost by: Bigbaldybloke » Fri Aug 24, 2018 5:23 pm

Fuel pipe is copper on mine
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PostPost by: Barney » Fri Aug 24, 2018 5:34 pm

Sorry I don't know if petrol or petrol vapour can be an electrolyte.

I would however expect there to be water at times as the atmosphere in the ullage space condenses as temperature changes in a normal diurnal cycle.
In large ship's fuel tanks, and under certain conditions, there is an understood process that can lead to bacterial degradation of Marine Diesel Oil, that can cause filter blockage and disable ships.

My personal experience is with Brass fittings and Aluminium Gangways in a marine environment on the deck of tankers..
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PostPost by: Bigbaldybloke » Fri Aug 24, 2018 5:45 pm

Thanks Barney, that’s good enough for me, I’ll drain the tank and fit fibre washers. Should cure two problems, the leak and future corrosion. Original tank was steel so wouldn’t have had that problem, instead it just rusted !!!
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PostPost by: alan.barker » Sat Aug 25, 2018 6:54 am

You're right , I think Fibre Washers is best like at the 2 Banjos on the carbs if you have Webers or Dellortos.
If the Fuel line from Tank isn't Plastic then it's been changed. Maybe a Kunifer, Copper, or Steel is better.
With a Copper tube and a Brass Olive it will seal better than Copper tube + Copper Olive.
I hope that fixes the leak. It's difficult to get to the Banjo unless you have added an access Hatch in the Boot.
Alan
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