[FJtest]

All that's wrong is that your fuel gage calibration has been affected by sloppy workmanship during the pump replacement.

The fuel gage sending unit is attached to the fuel pump assembly, and actuated via a float attached to a stiff wire 'arm'. If whoever is replacing the fuel pump assembly isn't careful when removing and reinstalling it in the fuel tank, they can bend the wire arm and create a wildly inaccurate fuel gage indication, which will also affect the point at which the low fuel warning light turns on.

Your fuel tank is fine, and still holds 19 gallons.

Your fuel gage calibration is off, and the fuel gage doesn't accurately display the true fuel level. The low fuel warning light is also inaccurate. The float arm needs to be tweaked back into its original configuration, or better yet the whole fuel level sending unit should be replaced.

Whoever does the work needs to be someone familiar with the FJC/4Runner fuel pump/fuel gage sender setup, and competent enough to remove and replace it without damaging anything.

 

[FJtest]

Here's a photo of the fuel pump/fuel gauge sender assembly, showing the wire 'arm' the float is attached to.

Unless care is taken during pump removal and re-installation in the tank, it is possible to bend the arm, affecting fuel gage calibration and low-fuel light trigger point.

A few years ago there was a massive Toyota fuel pump recall that affected hundreds of thousands of Toyota vehicles that use this type of fuel pump, and some percentage of these vehicles had problems with fuel gauge calibration because the float arms were inadvertently bent/deformed during pump replacement.

When I had my pump replaced under the recall, I had it done by a dealer who had replaced dozens of pumps, and my fuel gauge calibration was unaffected.