The motor inside the pump runs at high speeds because it needs to maintain fuel pressure, and a standard vehicle has about 30-60 PSI (per square inch), but can be as high as around 2000 PSI in direct-injection systems so you hear them hum. It is caused by the rotor and vanes within the pump seeking equilibrium with all operating conditions and, when precise levels of pressure are reached so as to supply fuel at just-the-right rate an audible hum emanates. Modern in-tank fuel pumps, such as those found on the majority of contemporary vehicles generate a familiar humming sound from their unavoidable running within enclosed spaces where noise is greatly magnified, particularly when the level of contained liquid reaches low levels.
The hum differs depending on which condition the pump is subjected to. Additionally, a louder-than-usual hum can indicate an inadequate voltage supply which causes restricted fuel flow with resultant increased motor strain and wear. Hence the advice from automotive specialists to ensure that fuel pumps get a guaranteed 12-14 volts, as inadequate voltage lowers fuel pump performance up to 15% which causes it louder. Regular voltage checks and high-quality electrical connections help prevent unwanted hum levels.
Fuel quality and contaminants can have an impact on the fuel pump hum as well. Impurities or rust in the fuel will result an increase of the load on pump, as a consequence engine began to hum louder. Fuel filters keep debris out of the system, and mechanics suggest OEM-compliant versions that can improve fuel pump life by 30%. The two largest fuel pump manufacturers, Bosch and Delphi use noise-dampening designs in their pumps as well by using high density materials for the casing to reduce decibels up 20-30 dB or more specifically where ambient cabin silence is a factor like luxury cars and performance vehicles.
Fuel pump insulation has also improved and combats any humming noise. Closed-cell foam and rubber mounts minimize vibrations, reducing noise output as well as cabin intrusion. According to the company, using these damping materials helps fuel pumps work more quietly and longer – up 8-10 years depending on use.
People like Henry Ford, he believed in quality engineering — “If I had asked people what they wanted, they would have said faster horses”. In the decades since, that same spirit of innovation has propelled our progression – every step from quieter motors to improved insulation not only boosted performance but also delivered critical noise reduction.
If you would like to learn more about the topics discussed above, refer Fuel Pump for additional information on next-generation fuel pumps designed and written with reduced operating noise.