1989 240sx no start

[nommarune]

ok so i bought my 240 3 days ago and they told me all i needed to do was add new gas to it. i changed the fuel filter new battery and 4 gallons of new gas to the preexisting less than a quarter of a tank. the car will turn over and try to start but there is no combustion. if you spray a lil carb cleaner in the intake she will turn over and run for about 5-10 seconds then bog out. not sure if i should dump the gas or change the injectors or the pump or both. car only sat for like 8 months. also the brake light switch is messed up curious if that may have anything to do with it. thanks for the help i am a rotary man this is actually my fiances car.