Floods on start...then runs fine

Howdy,
Boy this is weird! I have a 97 metro 3 cyl manual transmission. It will start up immediately run for a few seconds then die. Wont start again. HOWEVER....if i pinch off fuel line it will start. Then unpinch fuel line and it starts and runs perfect... How does this make sense and how do i fix it???

Thanks in advance to everyone
Ernie