Blows fuel pump fuse

This is the third occurrence. Engine started then shut off and won't start. Blows the fuel pump fuse. Previously, mechanic replaced fuel pump which did not resolve the issue. Finally found a short in the wiring where insulation was broken and grounding on frame. Worked okay for a while and now the same issue. Blows fuel pump fuse as soon as switch keyed. How do I trace the wiring to find the short? I have one of those circuit/short finders.