Fuses blow for good reason and that is excess current!

The reason for rewiring the pump is the old wiring degrades over time and builds resistance, hence the pump cannot draw the power it needs via it under load, this along with the fan loom are two chronic weak points on these cars which both need addressing!

I should think you have a short somewhere or possibly a problem with the pump, i.e siezed.

One thing you could do as a test is apply power directly to the pump and see if it runs?

Martin