starting problem

:banghead: i have a 1998 megane coupe cabriolet and i have problems starting it, if i turn the key to start it it struggles but if i turn it straight back off and satrt it again its fine, if it does start 1st time it judders and the revs drop to stalling mode you can also smell petrol, i have had the crank sensor done and the problem is still there, i really dont know waht it could be, has anyone else got or had this problem, please help??????
emma

Sounds like the engine is being starved of fuel especially if you say you can smell petrol....i would check for a possible fuel leak/blockage