electrial 1987 240

[scooter]

while installing a new radio in my '87 240, I touched the blue wire to the ground. the car was running and shut off immediately. We tried to start it and there was nothing. We triedagain after lunch and the car started with no problem. Later in the day it stopped running while driving. with the same symtoms anly it didnt start again after a break. Any Ideas? None of the fuses on the panel blew.