how can i fix my rover 216 coupe?

i am having problems starting my 216, when i first turn the key it will start but then engine dies straight away,then i turn the key and it won't start at all so i put a jump pack on the battery and it starts and dies straight away again and then won't start, i then take the jump pack off and it then starts and dies again it does start in the end but sometimes i have to repeat what i've said above up to 10 times before it evetually gets going.