I had this problem many times , I discovered the manufacture forgot to put the filters in the tank, I had to fit an external filter, which was much cheaper than the internal ones. the other problem was fuel getting into the engine. this was prevented by inserting a piece of fuel pipe up the bottom of the filter where it attaches to the engine. about a couple of inches long. and sealed in. this still allows the breathing, but the fuel can't get into the engine if the problem re occures , it will just leak out the drain holes at the bottom of the filter .
