Its one of two things. Likely, it is the fuel level sender which is part of the fuel pump assembly in the gas tank. You can replace the fuel pump assembly, but it is expensive. It also could be a bad instrument cluster, not very likely. Try junk yard for parts.
fuel systemfor 1998 chevy malibu
Where is the fuel filter located on a 1998 Chevy Malibu?"
the sending unit is attached to the fuel pump in the tank.
It is inside of the fuel tank.
The fuse box for the fuel gauge on 1998 Chevy blazer is located on the driver side. It is near the hook latch.
Put a fuel pressure gauge on it and that will tell you.
the fuel filter is in back just ahead of fuel tank.
The fuel gauge fuse on 1998 Chevy blazer is located in the front of the blazer. It is on the driver side next to the hook latch.
GM vehicles do not have a fuel pump inertia switch.
see link below for help Good Luck
on the 3.1 they are under the plenum on top of engine.
check your fuel pressure.