I need help with my 1994 basic cinquecento, why ever the fuel tank is over half full it runs ok , but anytime it is lower than halfway when i come to a junction and put my foot on the accelorator nothing !!! and then i have to pump the accelorator to get the engine revving , it even sometimes does it when driving along,bit of a fart and a splutter then it kicks in again, in my ignorance is it the fuel pump acting up ??? hope someone out there can help me