Ford explorer 2002

I have a 2002 ford explorer 4.0 v6. It's been sitting for 3 years before I was
able to get it worked on. I recently had the head gaskets changed,fuel pump,
the timing chain reset,and fuel pump relay fuse.I was only able to poured 2
gallons of  gas in it because that's all the gas jug could hold for the first time
in 3 years and it started right up. It was ran out by pressing the accelerator to
make sure everything was working properly. So I'm poured more gas in hope
it would started right up as it did the first time, but it hasn't. It's cranking, but
not starting. Someone suggested checking the vapor canister. Has anyone
had this problem as well where this part had to be replaced?