Fuel problem or possibly a sensor

Okay, bought the vehicle the guy said it had small issue with starting. Well after it turned over he pumped gas and it started. So I drove it home it ran great no noises or hesitations. Parked it for couple months because it wouldn't start after it was shutoff. So I replaced pump the wiring was all messed up to that got that fixed got new tank leak in old one the new tank was missing nipple to vent on front of tank so I blocked it and the hose now I have fuel going to rail up front I have spark but no fire just cranks I'm thinking sensor? But not sure if it's much worse or not. If it ran before just fine I wouldn't think it would be anything serious. Would the vent prevent it from starting? Please help I'm going insane trying to figure this out.