I replaced the fuel pump, fuel accumulator and fuel filter on my 1979 450SL in March of 2006 and have since driven ~3000 miles. It has now begun to make the loud "humming/buzzing" noise, indicating imminent failure. I never let the fuel tank get below a quarter of a tank and have replaced the original gas cap with a new OEM gas cap. What is the life expectancy of a bosch fuel pump? Could anything else be causing the pump to fail? I just can't see replacing the fuel pump every year.