Just at terminology issue; not everyone knows Auto Speak.
What I got from the description he has an intermittent short in the wiring near the fuse box.
If that is the case he will need to find the wires or wire that the Insulation has rubbed through an shield it or replace the wire.

However, also in the description concerning the "bump"; could also be a symptom of a loose/broken wire cutting off the electricity and, a resulting temp loss of power.

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84 300D, 82 Volvo 244Gl Diesel