How do I know if I need a fuel pump

1st>NEVER let the fuel level get less than 1/4 tank or you will burn the fuel pump up,sooner than later. the fuel pump must be covered with fuel at ALL times,this is what cools the pump to operate normally! you said *won't turn over* that means the starter motor isn't cranking the engine over,if that's what you mean then, fuel and cranking not related.if you mean it cranks but won't start,then check for power at the fuel pump.if you have power there at the connector,then the fuel pump is burnt up and will need replacing(located inside the fuel tank).around $300.00 at local parts stores.