turn phone off, remove battery, and use 80 -100% alcohol (available from chemist, not the pub) pour over the alcohol gently and in stages, this should flush out the fuel and the alcohol will eventually evaporate. if this does´nt work buy new display, remove old display, use the alcohol to clean the the inside out, wait till its clean and dry, fit new screen. and all been well iphone works a treat again
try the following:- be warned this will erase all data on the phone!!!! Hard Reset Turn the phone off. Press and hold the power button. When the phone vibrates, release it and press and hold the volume down button until you see the exclamation mark on the screen. Another way to do this - press and hold the volume down button and connect the charger. With the exclamation mark on the screen press this sequence of keys: -> Volume Up -> Volume Down -> Power button -> Volume Down if it does not react, remove the battery wait couple of minutes and carry out the above once again
I found after investigating this issue further it seems a common problem that there is a defektive chip on the mainboard that causes this problem. so if under warranty, get it repaired or exchanged for another. if its not under warranty anymore, maybe you could buy a broken iphone off ebay or somewhere like that, and swop mainboards.