fuel tank


when i fill my daihatsu f75 fuel tank it leaks deisel form around the tank filler area. is there an overflow?

Tanked Up

Yes there is an outlet, this is not an overflow though; the main filler pipe attaches to the body and runs to the fuel tank, it connects to the tank with a short rubber hose to absorb any vibrations.
A pipe is fitted to the top of the tank to expel air when the tank is being filled, this connects to the main filler pipe, and again is coupled with rubber hoses.
A tank breather is also connected, this runs to a plastic assembly, this contains a ball bearing and two springs, the two springs sit each side of the bearing to centralise it. As fuel is used from the tank, a vacuum is created, once this is sufficient to move the ball bearing it lets air into the tank to negate the vacuum, in hot weather the fuel expands and creates pressure, when this is sufficient it pushes the ball, letting pressure out of the tank.

Main problems usually are:

Rotten main filler pipe, due to its location it is often not cleaned and compacted mud sits around it.

Rotten rubber pipes, it can be any one of them so investigation is required.

Metal stub pipe on the tank corrodes, this is where the main filler pipe rubber hose connects to the tank.

Plastic breather valve rusts internally, the springs often rust siezing the unit, pull this off and use penetrating oil to clean the unit, lubricate periodically with engine oil and drain.