Q: no power to fuel pump on 1990 Chevrolet Suburban 1500

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replaced fuel pump was blowing the fuse(ecm-b)reassembled problem unsolved checked fuel pump with direct power runs fine replaced relay and checked voltage of relay connector no voltage except.3voltsfrom orange wire should there be voltage at other wires? also checked continuity of wires back to pump ok no visual signs of short or broken wires anywhere else.could this be ecm or oil pressure sending unit driving me nuts and runnining out of money to throw at it any help would be greatly appreciated thanks.
(2) Answers
yes, you need to find out what else is on the circuit. i believe that the oil sender is on the circuit. look closely at that harness and if it is ok, remove the connector and see if the fuse stays alive,

Roy is correct, it most likely is the connector where the pump plugs in. When the pump goes bad it melts the connector. Most of the time it's because the fuel filter has not been changed, causing a restriction in the fuel line, hence making the pump overwork, hence causing high amperage then melting the connector.