One way the water gets in is due to a blcoked or crimped drain. There's a drain under the top tank surface of the cap but above the actual rubber seal. This drain runs down to towards the back of the engine to drain anywater that gets in there, ie when washing or parked in the rain. This can get crimped, hinging the tank up pulls the pipe up slightly but when it the tank goes back down it can crimp the drain. Water then sits under the cap (but above the rubber seal), until that is when you open the tank and then it goes into the tanks, water is heavier than fuel so sits at the bottom and rusts your tank! Easily cured by making sure the drain hose is pulled down once you put the tank down to it's running position |