Tiger Shark Engine's (ANYONE HAVE ONE )?
It sounds like you might have a leak at the tank. Other than that, check to make sure the engine came with a head gasket installed. Also check to make sure that the back plate gasket is not broken. Just to make sure I didn't miss anything, you do have a copper gasket under the glow plug, right?
One of the students at our field had one of the 40 something size engines of this make. He flys O.S. now. Out of 10 people, not one of us was ever able to get it to run properly.
Good luck,
Silversurfer