Sounds to me like there's some wires crossed. This is as simple a circuit as is possible. The dashboard light has 12v power to one wire and the other wire runs to the fuel low pressure sending unit. When the fuel pressure is below 7 psi, the sending unit's internal switch closes and grounds. This completes the circuit for the dash light illuminates.
You can check the operation of the sending unit by connecting a test light to it. Run one wire to the + terminal on the battery and the other to to the spade terminal on top of the sending unit. Turn the key switch on. The test light should come on momentarily, then go off after the pressure builds to above 7 psi.
Sounds like you need to check the continuity of the present circuit wires.
You can check the operation of the sending unit by connecting a test light to it. Run one wire to the + terminal on the battery and the other to to the spade terminal on top of the sending unit. Turn the key switch on. The test light should come on momentarily, then go off after the pressure builds to above 7 psi.
Sounds like you need to check the continuity of the present circuit wires.