how to trouble shoot a 1994 ford f150? it turns over and runs only a few second……n?

the truck ran fine until it was parked for 4 months….now it will turn over and run….but it won’t stay running…what can i do to trouble shoot this? i have checked all fuses, i am going to put 3 gals of gas in each tank with a stabilizer…just in case of old or water in fuel…and i am gonna change the gas filter……what else should i do….?