99ram 1500 crank no start.

my pickup cranks but does not start. I've replaced
the following: battery, crank position sensor, idle
control valve, intake temp sensor, TPS, cap, and
rotor, spark plugs, plug wires, fuel pump and it still
wont fire over. it has spark and plenty of fuel going
to each cylinder. but it wont fire over unless the
gas is all the way to the floor.