one fuel tank overflowing

Good moaning.

So i have 2 40 litre tanks under the seats on my series 3 109, and one the fuel is flowing out the top when the engine runs and the other tank is 2 inches from the top..............? Parked on pretty level ground and problem is recent. (did clean air filter today and changes oil in gear box and engine, also tighted the hand break. Could i of caused it).

Any idea anyone?

Thanks

I had the filler pipe split on my 88.....

is it a diesel , if it is the return is probably going to the tank that is overflowing , so you need to select that one to use first . HTSH

i dont think i have a choice of fuel tanks?? they go down together. The fuel is not coming from a split pipe its coming from the hole you put the fuel in..... just flowing out the top where it went in??

it might be a blocked balance pipe, as it must be drawing from one tank and returning to other , either that or you have solved the worlds energy problems !!

just to update you guys, i do have separately operated fuel tanks, and one is returning the fuel and the other is drawing it but not returning it. Its leaking out on the return to the left tank. Still not sure why the other was filling up but i think the lever was not quite fully in position. Might need to replace the return pipe or try and clear it through as parts in Malawi arent that easy to get.