keep the iBook in heat of sun light 4 to 5 days and clean the system
coffee should be dry and remove the keyboard and check the it that the liquid dry also pass the current to another component. After this you on the Ibook
This is a problem of hdd or dvd . First boot form external DVD rom. and check i hope it work. Some cases hdd fail change to new one. rare cases you need to clean the board of G4.
If there is Nvida Chip you have a problem. Because of the Nvida chip heat more compair to Intel and Ati. It can be Problem. You have search the chip level repair. there the heat the Nvida Chip and Press. It work in 90% computer.
If doesn't work all three option 1 change the Keyboard 2 open the hardware DVD drive and take out drive 3 when you boot up press the eject button so many cases it work.