you tried to change the relay and look for a water leak /damp check the gromets near wear the loom goes though PLUS WHEN A ALARM OR IMMOBILER IS FITTED SOME FIT IT NEAR AND TO THAT RELAY TO CUT THE FUEL CHECK THE WIRE IS NOT SHOWING IT COULD BE SHORTING TO EARTH ANOTHER IT THE ISOLATOR SWITCH IN THE BOOT LOSE WIRE CUZED MINE TO BLOW BEFORE