Usually, a loud fuel pump is an indication of pending problems that require immediate attention to prevent performance issues. Normally, a fuel pump is quiet; there can be a low hum heard when the pump works at a pressure, usually maintained at 30 to 60 psi for fuel-injected engines. Most of the time, the noisiness emanating from the pump is due to various factors, including low levels of fuel, filters clogged with debris, or internal wear.
Low fuel is probably the most common cause of fuel pump noise. The fuel inside the tank helps in cooling the pump. If the fuel level drops below a quarter of a tank, the pump may start pulling in air and can start overheating, thus becoming noisier. Running a fuel pump on low fuel constantly can reduce its life by as much as 30% due to the added stress, and this is the reason why car experts recommend that one should never run on less than a quarter of a tank. In fact, a study by the National Institute for Automotive Service Excellence reports that running the fuel frequently low is responsible for almost 15% of early fuel pump failures.
Some clogged fuel filters are another common source of noise coming from the pump. Since a blockage point is reached in the filter due to debris, rust, or sediment, it makes the pump work much harder to create adequate pressure, which is then louder. If one replaces the fuel filter every 20,000 to 30,000 miles to prevent buildup, it will keep the pump operating efficiently and can be avoided. Avoiding clogged filters can less likely provide the possibility of noise in the pump and extend its life cycle. As a matter of fact, a good quality and well-maintained filter supports the pump operating at optimum efficiency, reduction of noise, and fuel economy.
Wear and tear inside the pump also contribute to making noise. After some time, it deteriorates internally; that is why the motor or bearings wear out, and as a result, louder operation of the pump occurs. This is quite a common thing in cars with big mileage because the pump has been operating for several years already. For this, such pumps may need replacement if they are over 100,000 miles old and start making excessive noises for quiet operation and consistent fuel delivery. Generally, all high-quality replacement pumps are more durable, with materials that resist internal wear longer compared to their low-cost alternatives.
Besides, design and increased flow rates might also make high-performance or aftermarket fuel pumps noisier. These are higher-rated fuel pumps used on a turbocharged or modified engine and are capable of giving out fuel flow rates greater than 100 psi, thus generating noise greater than that generated by a conventional pump. In general, though, such noises are generated by high-performance applications, and their drivers are said to consider this a price they have to pay for the high performance and flow of fuel.
Noisy fuel pump operation should not be tolerated, because it can be a precursor of pump failure or low fuel economy. For more information about choosing the right pumps and troubleshooting noisiness go to Fuel Pump.