While trying to fix a fuel Gauge I discover that the fuel pump wad straight wired

You must have measured voltage at the fuel pump with the key off?
Are you saying you found a wire that goes directly from the Battery to the Fuel Pump, uninterrupted?
Do you hear it running?
What Make and Year of Vehicle?

U don't hear it running with the switch off
He had it plug in to fuse that comes on with the switch. This is 87 with fuel injection. It had dual tanks but on one works. Why would he straight wire the fuel pump.by the way the fuel gauge is way pass full

No sure about what you mean as straight wire. "with the switch on" Ignition switch? Its supposed to work that way. There is a fuse or relay energized from the key circuit to the fuel pump in position 2. That way, the pump only runs when running or trying to start the car.

Being an 87 narrows it down, Honda?
If you pull the fuel pump relay and it still works, it is bypassed.
If you pull the Fuel pump relay and it stops, then they may have connected to the circuit directly due to a bad/corroded connection?

Being an 87 narrows it down, Honda?
If you pull the fuel pump relay and it still works, it is bypassed.
If you pull the Fuel pump relay and it stops, then they may have connected to the circuit directly due to a bad/corroded connection?

"dual tanks" sounds like a pickup truck.

ma0641, when you said position 2(II) I thought you knew some additional info?Make?
Ask whoever did it, If you bought it like that, Check Fuel Select/Sender Valve/switch was not bypassed, when it switches tanks, it also switches sender on Many.

On this 87 Chevy silvrado I replace the switch in the inside the truck& the fuel system select valve but fuel gauge still doesn't work if u ground

If u ground one of the. Wires ruwnning to the fuel valve the gua.. ge. Will move but fall back to full .what else can I try

You will need to find the colors for the senders, grounding of the fuel select may blow a fuse.
Momentarily ground should show movement as long a the gauge is good, has power from ignition and a momentary ground to move needle. You will need someone inside watching gauge, or run a jumper to where you can view the gauge while shorting.