You are correct 1987 Ford motor is gas carbureted There is but one 36 gallon tank. Here is what I see. The fuel pump relay has 4 pins and 4 wires. #1 pin is black ground #2 is power red/yellow #3. is pump power red (pink)/blk #4 blk/yellow inertia switch. The relay is good and the wires check out as in volts. The inertia switch is not tripped. When I jumpered #3 and #4 to manually start the fuel pump it did nothing. I jumpered the oil pressure switch and nothing. I checked all the fuses in box both sides of fuses with multi meter looked good. I simply can not figure why when the electric fuel pump when first put in tank it starts right up and everything is great. But then it suddenly stops working and that is the end of that pump, (3) times this has happened. maybe my vin number would give you the correct wiring diagram here it is: VIN# 1FDKE30L9HHB83879
