1991 GMC Other

Electrical problem
1991 Other GMC Models V8 Two Wheel Drive Automatic 95000 miles

My son has a 1991 Surburban. 2 months ago it blew the ecm b fuse. I replaced it, everything was fine. Then it started blowing the fuse again. Sometimes he could drive it for a couple of days, other times not. I did some troubleshooting, it seemed to be the fuel pump. So I replaced it. Started just fine. Two days later blown again. I'm sure something is shorted but checked harness could not find anything obvious. I would appreciate any help in the right direction, for this is his only transportation for work.
February 4, 2008.

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