Fuel tank breather

[AndrewR]

I have just completed the build of a Westfield Sport 2000 with the new FW bodywork fitted.

I believe on the old style bodywork the fuel tank is mounted quite low on the chassis, I believe that you run a pipe from the tank breather up the chassis leg.

On the new bodywork the tank is mounted much higher, in the area over the diff. This means that the top of the fuel tank is within 5 cm of the uppermost bodywork .

On my car there is a alloy (Red) breather  on the top face of the tank facing up. In speaking to Mark at W/F he said the breather must have a pipe on it, and to run the breather pipe over the top of the tank. I then then ran the pipe down the side of the tank, and then back up vertically so the end of the pipe is at the highest point on the car.

The car is nearly full of fuel, this p.m I have had the heater on in the garage. I have found that it is pushing neat fuel through the breather onto the floor. When I open the fuel filler the fuel level is slightly down from the filler

I thought the breather valve was meant to let air into the tank, but then stop liquid fuel passing the other way. Could the valve be faulty?, it is very hard to get to the valve now - what if I buy an inline non return valve and fit it to the end of the breather pipe

Any thoughts?

Andrew

[pistonbroke]

It lets air in to displace the fuel you burn when the engine runs .

If the tank is filled to the brim with cold fuel as the fuel warms it will expand , the only place for it to go is out the breather .

cure is to not  overfill the tank  

[tex]

the valve i have is nothing more than a ball bearing which slides up and down - if you roll it it shuts the valve - the valve must be mounted vertically - is it  the right way up?

[AndrewR]

Thanks for that the valve is an alloy one that screws into the top of the tank, the valve is vertical and only will fit one way

Regards

Andrew

[perksy]

I then then ran the pipe down the side of the tank, and then back up vertically so the end of the pipe is at the highest point on the car.

Any thoughts?

Andrew

Just wondering if you've kinked the pipe and it's shut off internally    

Ideally it needs to go just straight up with no serious bend/s

[combatsapph]

Is the filler cap higher than the vent valve?

If so, fuel will obviously leak out of the valve if the tank is filled level with the filler cap.

As a previous poster mentioned, the valve isn't technically a one way valve - it's just supposed to shut if you roll the upside down (ball bearing slides in to the valvle outlet).

For the benefit of everyone else, this is the valve being talked about:-

Bottom leftt hand corner (mines a long range tank though).

And inf you look at the following photo - my filler cap is certainly higher than the vent valve - that's why there is supposed to be a pipe on the vent and to point it upwards.  best to use fuel resistant pipe as well ;-).

[AndrewR]

The valve that I am talking about is the red alloy one on the front left of your photo. With the FW bodywork the tank is smaller, and is mounted on top of the diff on a steel frame.

On the FW bodywork there is only around 5cm from the top of the tank to the underside of the body work. All I could do was attach a rubber pipe to breather, and run it along the tank left to right, then run the pipe down the end of tank then turn it vertically so the end of the pipe finishs just below the fibreglass body work.

Last week I filled the tank to within 10cm of the top of the tank, over the weekend I was working in the garage with the heater on. At some stage I begun to smell petrol, there was petrol dripping out of the rubber breather pipe.  I have also noticed that when I drive the car up the slope onto the trailer, fuel gets pushed down the breather pipe.

[combatsapph]

Hmm, in that case I don't know but its deffinately not right  

[pistonbroke]

Sounds as if its syphoning out through the pipe  

I would try re- routing the pipe or maybe fitting a syphon brake. trouble is you dont have much room .

Have you spoke to the factory about this ?  think its a bit dodgy having fuel slopped all over the garage floor

edit to say ....

Just seen your photo and yours is exactly the same as mine . The difference being I only have a short pipe run which goes from the breather , up as high as possible then cable tied to the chassis rail , it doesn't go below the level of the tank at any point .

maybe thats why yours is syphoning try a shorter pipe m8 .