[Rovernet] Sd1 fuel pump woes

[Jess Rainey]

Any help out there would be appreciated. 
Electrical problem to fuel pump for carbureted engine. Pump is in tank, not external like efi
No fuel to carburetors, but can apply current to pump and then fuel gets to carburetors. But when in this arrangement and attempt to crank engine, speedo goes to 145 km and then breaker opens and speedo goes to zero. Engine does not crank. Without external power to pump engine cranks, but of course does not start as no fuel. 
Electrical to pump is grounding out. Question: with these presenting symptoms any ideas as to where short is located?
Car is 1985 sd1 2600
Thanks is advance
Jess Rainey

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