Won't start cold-blows fuse on new overvoltage relay

My 86 190E ran great until it blew the fuse on the overvoltage relay, then it would not start cold. I replaced the fuse and it worked fine for a week then blew fuse again. When I replaced fuse second time...would not work...no cold start. Took car to shop, they charged $600 and replaced fuel pump relay, idle stabilizer, and god knows what else, now it barely starts when cold but still not right.

Today I bought a new overvoltage relay (since that seems to the the most recommended part for this problem in your forum). As soon as I turned on the ignition with the new overvoltage relay, the 10 amp fuse on it blew......Now what??? please help, I live in the mountains and can't use a car that won't start cold.
Bought car new in 87, has 189,000 miles still love it.