I am having some trouble with the breather system on my fuel tank and need some help on how to rectify it. I only have a single side fuel tank on my KVA and when I fill it up trapped air in the tank forces fuel up the main pipe and overflows everywhere. This problem would not make me very popular at filling stations and I am stumped on how to sort it out.
To give you an idea on how it is set up at the moment I have a separate breather pipe that runs to the inside of the cap (taken from the highest point of the tank itself). This then does not let air escape when the cap is shut. I have installed a breather at the rear of the tank over the weekend with a two way check valve inside. I had hoped this would help but when I filled the car up with fuel it entered the tank ok, and then trapped air forced it to overflow again.
Could anyone please advise me on what I can do to sort this out. Does anyone have a diagram of how the tank vents on their cars are done. I really need to get this sorted out. It overflowed when it was sat in the sun last week due the heat expansion. Any help would be most appreciated.
Hi Simon'
A few questions about your system:
Is the fill tube attached to the top or the side of the tank?
Does the tank have baffels that are closed at the top?
I doubt the problem is due to venting, as the air should be above the fuel and therefore should exit the fill tube and or vent tube first.
Also, when is this occuring, during fueling, or later after the the fuel has warmed up and expanded?
Thanks for the reply to my problem. The main filler pipe is located at the front end (not directly on top). Right next to it is the breather pipe using a 12mm bore hose. As far as I am aware the tank only has one baffle divide right in the centre. I am unsure if this divide has an opening top and bottom because it came with the car when I bought it. The overflow problem happens when I fill the car from cold. However when the car has been in the sun the same problem occurs if the tank is quite full. If it is not the breather set up do you have any thoughts on other things I should look at?
Simon,
How big is your vent at the back of the tank? Can you take a pic of its set up?
Brett
__________________ Southern RSGTD; Mexican block; Audi 01X
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Ford had a similar problem in the 80s with vans that had a fuel fill entering the side of the tank. This allows air to sit above the fuel and become pressurised as it and the fuel become warm. After a number of fires they had to recall and modify. I would add a vent to atmosphere on top front of the tank. also with a valve as you did at the rear. That should remove any remaining pressure. I am surprised that the the pressure did not expell fuel from the rear vent. Are you using the type of valve that stops flowing in the presence of fluid?
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