My iphone 2g wont turn on, i replaced the lcd, it

my iphone 2g wont turn on, i replaced the lcd, it worked ok, my batter was low. so it died and i was trying to turn it on, but it wont turn on. when i plug in the wall charger nothing happens,but when i press on the on button while charger pluged in, apple sign comes on for 2 second everytime i press on the on button, but it wont turn on. and if i try it without charged plugged in, nothing happens? any idea