1998 Rover 2 Series wont run

hi i have a rover 200 petrol it was left for a week and i tried to start it last night but it was just wouldn't go so i top it up with some more fuel and tried it again but it wouldn't go so i rolled it down the hill and it back fired a ran but as soon as i took my foot of the accelerator it stopped so i tried some easy start in the air intake and it wouldn't go so i got a tow to the the top of the hill and rolled it again and it went but stopped as soon as i took my foot of the accelerator again so i leaned the distributor cap but didn't get any progress ca you try and HELP me out what i could try next

thanks joe