Fuel tank capacity for a 98 fordf150 2wd 4.2liter regular cab

SOURCE: 1992 f-150 dual gas tanks tank closest to cab of truck pumps gas out the fuel cap

A FORD EQUIPED WITH DUAL TANKS THIS YEAR MODEL HAS CHECK VALVES IN THE FUEL PUMPS .THE FUEL RUNS FROM THE REAR TANK WHEN IT IS POWERED ON TO A TEE AND INTO THE SAME LINE AS THE FRONT PUMP . THE PROBLEM IS AT THE BOTTOM OF THE FRONT FUEL PUMP THERE IS A CHECK VALVE ON THE FOOT AND IT IS NOT WORKING.WHILE THE TRUCK IS RUNNING WITH THE REAR FUEL PUMP ON IT IS PUMPING FUEL INTO THE FRONT TANK . IT WILL RUN OUT OF THE NECK WHEN IT IS FULL.THE FIX IS SIMPLE REPLACE THE FRONT FUEL PUMP. THEY DONT MAKE A CHECK VALVE REPLACEMENT I CHECKED I HAD THE SAME PROBLEM AS YOU.

SOURCE: Just bought an old 1988 ford ranger extended cab

I believe there were two options 15-22 but i'm sure you can find out by filling it when its almost empty