I have fuel, air & spark...what else do I need?

I just changed the head gasket in my 1996 Tacoma 4x4 2.7 speed. I can't get the truck started. I have fuel air and spark. The timing marks are correct at TDC on cyl#1, cams & crank pully. The plugs wires cap and rotor are all new. I am getting spark at all 4 plugs and fuel. I can't figure this out and we are suppose to get a large snow storm within the next 48 hours. Please help!

 

Do you have enough compression to create an explosion in the cylinders ? The only thing I could think of.

 

That is the only thing I haven't done yet. I am going to autozone to rent a tester. What would caust not enough compression? thanks for the response.

 

I would recheck the torque values of the head. Have someone else crank the engine, and you get under the hood and listen for odd or improper sounds.