ok so first what you should do is take the glow plug out and take out the rings that should be inside,there should be a way to look in the motor ifyou shine a flash light in it and there are seals that could be busted if that is your problem your looking at paying any where from 50-80 dollars to get them replaced or get a new motor........................ or you can take it in where you got it and pay 5-8 dollars for them to check for anything.
Hope it helped!