Petrol fumes + 2

[Carlton]

Good afternoon

My plus 2 has a vented Petrol cap. Do I need keep the two vented pipes at the petrol tank sides, or can I lock them. It smell to petrol. Perhaps I can add a carbon canister like MGB and E Types USA specs with unvented tank

Thank you in advance for the advice
Regards
Carlton

[Matt Elan]

Couple of points. Your filler cap should not be vented as the tank breaths through the two vent pipes. There were lots of versions of the cap used on many cars and motorbikes some of which were vented. You can get repair kits to replace the seals and the vented plate from the original manufacturers Ceandess Ltd. There are two seals on the non locking cap, and an extra ‘o’ ring on a lockable one. The vent pipes also mean you can fill the tank to the top - the filler pipe enters the tank halfway down the tank side and if there were no vent pipes filling up will be very very slow (as opposed to just slow ). The standard system can smell of petrol but it should not be bad. If it is then there is another problem - leaky tank, feed banjo or the pipes themselves. Having a vented cap won’t help with petrol smells as the vapour outlet will be higher than the vent pipe outlets in the sills. More details in my latest book ‘Lous Elan and Plus 2 Source Book’ hths Matt

[Carlton]

Hi Matt, Thank you very much for your reply. There is no leaking in the tank, it’s a new one, and the vented pipes are new too.
The Petrol cap is the one with lock and the plate has a little hole. So I assume that is a vented one. I changed the inner seal at the back of the the cap inner disc for a longer one because it leaks petrol when cornering, now is not loosing petrol any more but the fumes are still there.
The tank having the pipe at the middle is a must that needs the top vent pipes for be able of filling untill full to avoid an air bubble with no exit in the tank.
What do you think about fix a no return Valve on each vent pipe, that only let income air, plus an extra pipe with a T coneccted to the Petrol filler tube who let the air circulate and fill the tank untill full

[Carlton]

This is the petrol cap with the small hole in the plate

[Carlton]

New Petrol tank

[mbell]

You are experiencing the two common issue with +2 fuel tank setup.

The tank needs large vents to be able to fill, these vents allow fumes to easily escape. There is common mod to connect the large diameter vents to the filler neck and then install small diameter breather, possibly with a special valve (not a one way one).

The leaking cap is because the cap seal is spring mounted, under cornering the weight of fuel can push on it and un seat the seal. The common fix for that is too fit a valve from a mx5 filler neck o to the +2 filler neck. I've made a different mod adding a extra cap under the filler cap but haven't filled the car up enough to test it.

It can also be tricky to get a good vapour proof seal on joins and connections.

[Carlton]

Thank you very much for your advice.

[HCA]

Carlton, do not fit simple one way valves to the breather pipes on the tank - they will not solve your problem.

Back in the sixties and seventies all cars smelled of fuel. It is a wonder we are all still alive! This was because pressurised fuel tank technolgy did not abound, so all tanks were just vented to atmosphere.

You have two issues: fuel sloshing out the filler cap when cornering and the general smell of fuel around the car.

To fix the cornering issue, yes, you can fit a flap valve from the MX5. Does the trick.

Or kill both issues with this:

Make sure your filler cap is airtight with good rubber seals and then solder up the vent hole in the centre of the cap. This is most important. If you cannot seal your filler cap, use an inner cap such as: https://www.caplugs.com/recessed-button ... umber=BP-2 If you cannot find an inner cap, some have used a few layers of cling film to effect!

Then join the vents on the tank together with a pipe and fix one end of this pipe to the filler neck and the other end to a TPV-8 valve and vent this to atmosphere. It is important to use a proper TPV, yes they are expensive, and not skimp by using a simple one way valve.

With this properly installed you will solve the cornering and smell issues as well as meeting the roll-over safety - but only if you use a proper TPV.

[Carlton]

Thank you very much for advice.

This TPV 8 from Newton looks fine,

https://www.newton-equipment.com/tank-v ... -tpv8.html

The TPV 8 is a one way valve, only open in both ways under too much pressure, and its not a filter of fumes.

So it can be fitted for intake air from both vented pipes ? and connect both pipes to the filler neck for vented through the vented cap ?

Your idea is in reverse way, vent the fumes through the TPV ´s to the atmosphere ?? But the TPV ´s does not filter any fumes, and probably will remain the smell to petrol. The TPV´s are not a carbon filter, its just a one way valve, and I think that perhaps works much better for intake air to the tank through TPV´s , not for vented it, and if the circuit is also connected with a T and another tube to the petrol neck using a vented cup, it breaths through de TPV´s and vents through the vented cap. Don´t you think it works better ?

Another idea is add a carbon filter like the one of the MG´s and Jaguar E Type USA Specs for unvented petrol tanks but I don´t like the idea that perhaps the petrol will fill the carbon filter been worst the remedy than the problem.

I ready have one canister / carbon filter , but not sure if its work in the Elan for that reason.

[Carlton]

Carbon Canister

[Carlton]

Carbon Canister view

[HCA]

You said you had cornering issues. A carbon filter will not stop this. The TPV will minimise fumes, but I appreciate that in the Canaries, you have more sun that will help pressure build, in which case you can vent the TPV to atmosphere via a carbon filter.

[Matt Elan]

Hi Carlton
You do have a vented cap; as I said that will tend to vent fuel both when cornering and at rest when the fuel in the tank warms up. Also I can't make out from your picture if you have hose clips on the ends of the vent pipe where it fits onto the tank, you should have. Finally your vent pipe looks old (so presumably the other side is too) - it is yellow and is probably quite stiff and could be cracked somewhere along its length. If you want to see if the vent pipes are the source of your petrol smell then blank off the outlets in the bottottom rear of the sills and see if that makes a difference - if the small goes away then it is the vent pipes if it doesn't then there is another source of the smell - the banjo connection with the fibre washers onto the tank and the olive connection that joins the fuel pipe to the banjo both can leak. Fixing the banjo joints on my Plus 2 solved my fuel smell issue and I've still got the standard vent system. I may get a slight wiff if I fill the tank up to the top and park the car in the sun but otherwise no smells. You can just see the banjo by taking a wheel off; it should be completely dry so worth a check.
HTHs Matt

[mbell]

The TPV 8 is a one way valve, only open in both ways under too much pressure, and its not a filter of fumes.

The TPV 8 allows air in the tank under a slight vacuum, e.g. caused by the engine using fuel. IT will allow the tank to vent to air under higher pressure, generally simple evaporation of fuel won't cause enough of a pressure rise for it to vent. It wlil only vent if the pressure gets too high (e.g. full tank and left in sun).

So it should stop any fuel smell from the vents in all but exceptional circumstances.

The flow rate of the valve will be quite low thou, so will need the modification to connect vent lines to the filler neck during filling.

[Carlton]

Thank you very much for the advice and help. The vented pipes are new, they are yellow from new and the picture does not help. I’m going to buy the Newton valves and add the extra pipe to the Petrol neck. I’ll keep informed with the progress. Regards