My buddy has a 95 f150 5.0 and his front fuel gauge doesn't work but his back one does and he said fuel pours out of his front filler cap. Is this common? What could be the cause?

 

The cause is a bad check valve in the front pump. That pump either needs replaced or removed and the lines capped off.

What is happening is the FPR sends excess fuel back to the tanks to regulate pressure, the same line goes to both tanks. It is the check valve in the pump that, when off, is closed and doesn't allow fuel past forcing it to go only into the tank with the running pump, thus not crossfilling tanks. Over time, and usually through non-use, the check valve will simply give out allowing fuel to enter a tank that is not currently being used to supply the engine with gas.

Bonus: His front tank is completely full of gas, that's like a 16 gallon bonus.