finally got my car together and went to fire it up and it wont start... it cranks, but wont turn all the way over... i got spark, i spray starting fluid into the throttle and still wont fire... what can i look at as a culprit? timing and everything is good... PLEASE help!!

i have spark, i used starting fluid, which should start it whether i have fuel or not, and everything is connected and put back together....