Intermittent fuel system short

the fuel system will shut down when i shut off the truck but only if i turn off engine but leave the key in power in the on pos i heir the fuel pump running then i shut it off and tray to start the fuel pump will not run is their a common short in the fuel system .but i had it towed home now the pump is working.where should i start looking for the short

this is for a 98 2500 suburban

i did change the fuel pump relay. still the same