Petrol flooding ------------

[Helloween]

Hi, on a few occasions i go to start my car and turns over to start but then floods and battery eventually dies e.t.c., when taking the sparkplugs out there black or even sometimes little wet with petrol, i gave them a clean and start the car and fires up like noting happens now these spark plugs are new like a couple weeks old.. does anyone know what causes the over fueling? or anyone had this problem before? could it be sensors giving false signalling to the ECU? the car is a 1.0L and in a couple of weeks ill be having an engine transplant to a 1.3

any comments appreciated, at least would give me a light to look upon to get this problem sorted!!

Cheers

J