glowplug light wont come on vehicle wont start?

at first the light was intermitantly coming on and was slowly getting worse. ive checked the fuses and found the main 80 amp fuse in the engine compartment blown. i the traced wiring and found the 12v wire to this fuse rubbed through on the body underneath the electrics box ive since repaired this wire but still no joy. ive checked all wiring to the glowplugs and the glowplugs all seems ok. ive even tried a doner glowplug relay but still with no joy any ideas??? regards craig