Lotus Elan and Lotus Elan Plus 2 Forums

Hi

I know that the fuel smell is a common problem in the plus 2. Before I started the restoration of my plus 2 I had the same problem. Now I have a new aluminium tank but I don?t know the best way to solve the problem with the petrol smell.

Best Regards

Diego

There a lot of information on here about re doing the tank breathers so that you don't have two large breathers venting to atmosphere which is biggest issue with +2.

You probably want to do that and replace/update all the rubber connections with modern ethanol safe rubber while there.

If you search the archive on here there is a mod using an MX5 non return valve in the fuel filler and venting the tank back to the filler neck i've done this on my 130/5 and it works although the tank fills slowly

The only thing you need to do is join the two vents into one.

two vents creates airflow across the tank and fumes.

join the two just above the tank, loop one line above one side vent and down rather than over the headliner

done

Hmm.. This is interesting! Like Diego I am also interesting in solving the fuel smell issue on my +2S130 and the idea that gus has put forward I haven't heard before and seems a much easier a fix, if it works, than the filler pipe and MX5 non return mods.
It would be interesting to hear if others have tried this and how successful?

Personally I joined the vents in the middle, added large vent to filler and added narrow vent to atmosphere inside one of the original vent tubes. Seems to have done the trick but I've not put more 1/4 tank in my car....

The tank needs wide vent pipes to enable filling, as the filler enter half way up you need a method to allow the air from above the filler neck entrance point in the tank to vent fast enough to allow the petrol in quickly. So you need to keep a wide vent somewhere for filling which makes it easy for the fumes to escape if that is a permanent vent to atmosphere

The other purpose of the vent pipes running over the roof is to stop fuel escaping in a roll over. If you have a vent that just loops up on one side of the car it maybe possible for the fuel to leak out via it in a roller over situation. Which isn't very desirable.

The method I used is the tried and tested method used for years. If you go this route you can also use purposed design valve on the narrow vent line that only vents at high tank pressures, allows air in under normal usage and provides roll over protection.

A MX5 valve can be added to the filler neck to address full spillage from the filler neck on to the body under cornering.


So you If you just join the two vent tube together the top of the tank is sealed and the air can't escape which is likely to cause you problems filling the tank past ~1/2. I haven't tried it like this so can't vouch that this is the behavour you'll see

I?ve done the mods on the vents, the bit that stops fuel running out if you happen to roll your car is the fact that the vent lines finish in the wheel arch below the bottom of the tank (with the car the right way up!). Hence if the car is upside down, these pipes are above the tank so fuel won?t run out.
Mine still has a slight smell of fuel and I?ve found that it seems to be coming from the banjo fitting to the new alloy fuel tank has the tiniest weep from the fibre washers used on the bolt. I plan to change them out for alloy washers. It can?t be coming from anywhere else as I only put a couple of litres of fuel in the tank.

..a picture always helps

PS: the small vent pipe was eventually extended and routed up and around the rear of the window and then it pokes out via a 8mm copper nozzle below the wheel arch/floor

gus wrote:The only thing you need to do is join the two vents into one.

two vents creates airflow across the tank and fumes.

join the two just above the tank, loop one line above one side vent and down rather than over the headliner

done

If you do that it means the only Vent is the Filler Neck.
So when you have more than a Half tank the Air in the Top of the Tank will expand and push Fuel out the Filler
Please don't ask me how i know
You need some sort of Vent from the Top of the Tank even small.
Alan

I think the vent lines do need to run over the roof or at least do a full loop of the tank. If they just go directly down and exit the car in the normal position I agree they won't leak if the car is full over turned and on it's roof. But if the car is on its side one there potential for a vent to be lower than the fuel level in the up ended tank and therefore fuel can drain out.

So the vent lines needs running in such away that in all rotations the vent is above the "top" of the tank. Preventing it from draining out, running the vent line(s) over the roof is one way to do this.

Strange that's how Lotus designed it
Alan

alan.barker wrote:

gus wrote:The only thing you need to do is join the two vents into one.

two vents creates airflow across the tank and fumes.

join the two just above the tank, loop one line above one side vent and down rather than over the headliner

done

If you do that it means the only Vent is the Filler Neck.
So when you have more than a Half tank the Air in the Top of the Tank will expand and push Fuel out the Filler
Please don't ask me how i know
You need some sort of Vent from the Top of the Tank even small.
Alan

No

The filler neck is not a vent, the vent that I described connects the two vents then goes up over the c pillar vent and down through the floor in the stock location

One vent on one side not two

adding vents to the filller vent does nothing to reduce fuel smell. I have none and zero fuel smell[well no more than any pre 1971 car]

If your filler neck is not sealed it is worn out

The reason you go up is to prevent fuel sloshing out of the tank when it is full, or the lines staying full of fuel in a similar situation

It's a little known fact that ping-pong (table-tennis) balls are resistant to petrol. The pair I tried were, anyway.

Although I never finished construction it seemed an obvious valve item to allow fast air flow but block the pathway at other times and would fit on the end of the tube under the car. My prototype used offcuts from exhaust pipes mounted concentrically etc.

And yes, I've still got both balls.

There are purpose designed valves for tank vents that let air in freely as fuel is used and act as a pressure relief valve to prevent the tank being over pressured when filling or due to temperature such as leaving the car in the full sun.

Resurrected thread
But I just installed a couple of the aforementioned Newton valves and it solved the problems immediately.
They aren?t cheap and I used one on each side, but they are easy to install, do not require messing around with the existing hose over the roof and work !
When I had installed my new Axminster fuel tank and electric fuel pump I have inserted an additional fitting between the tank and the vent pipes, so I was able to simply place a valve on each side.
I did take the shelf out to give myself a little more light and room, but it is probably the most impactful 45 minute job that I have done on the car this year.
N