my renault megan scenics fan belt broke i put a new on an it wont start?

first its a (deisel reno megan scenic)i noticed a slaping noise and it turned out to be the fan belt in strips it snaped as soon as i opened the bonnet as the engin was running. i was just at the parts shop for some copper washers lucky realy? i got a new belt fitted it tried to start it the hole car shook the engin sounded awfull onece it started then stoped as i let go of the key? thers a weard buzzing coming from the ijector pump when the ignition is on no wires broke or plugs caught as i can see and the light that flashes on the dash for the imobelizer does not come on so i cant try the reset code by pressing the central locking button and it will sometimes fire but when starter is running. ext. any advice will be graitly apreceated thanks