Abnormal noises of the Fuel Pump usually result from internal mechanical wear or system incompatibility issues. According to the SAE research report, in case the gap between the pump casing and impeller is greater than 0.3mm (factory-set value is between 0.1-0.15mm), the variation of flow will generate the high-frequency noise of 30-50 decibels (dB), and meanwhile, the fuel pressure deviation will be raised to ±15%. For instance, in 2022, Volkswagen Tiguan L experienced a chain of complaints that were caused by worn-out impellers. The test for recall found the failure rate of the pump body that had excessive clearance to be as high as 18%, and the noise dropped to less than 25 dB upon replacement. Furthermore, when the life of the motor carbon brushes falls below the design life (typical 150,000 start-stop cycles), the frequency of electric spark raises to 5000 Hz from 2000 Hz, and it makes a “sizzling” noise. For instance, 2019 Nissan Sylphy owners complained that the risk of abnormal sound increases to 34% for a car driving for 80,000 kilometers.
Fuel contamination and rust in the pump casing is another major cause. If the accuracy of the filter screen is poor (such as more than 50 microns), the risk of particulate material passing into the Fuel Pump impeller increases by 27%, causing blade impact sound. The 2021 J.D. Power survey shows that in areas using ethanol blend fuel (E15), the rate of internal rusting of fuel pumps caused by the hygroscopicity of ethanol is three times as high as regular gasoline, the dynamic imbalance deviation of the impeller exceeds 0.5g·cm, and the noise amplitude is raised by 40%. A typical illustration is that the failure rate of the Ford F-150 in the Midwestern North America ethanol fuel region (12%) is much greater than it is elsewhere (4%). In addition to this, for fuel water content greater than 0.05%, the tendency of Cavitation in the body of the pump (Cavitation) increases by 15%, the noise of “bursting bubbles” is heard, the fuel flow rate decreases by 20%, and the power of the engine decreases by 8%.
The design and installation defects cannot also be ignored. When the resonant frequency of the fuel pump bracket happens to align with the vibration at the idle state of the engine (about 25-35 Hz), the level of noise is magnified threefold. In the case of the 2023 Toyota RAV4 Hybrid model, due to the insufficient torque of the mounting bolts for the pump body (design value: 8-10 N·m, only 5 N·m actually), the noise at the peak during idling speed reached up to 55 dB. After recalibration, it dropped to 32 dB. In addition, when the return fuel valve spring stiffness is lower than the design value (for example, the design value is 120 N/mm, but the actual value is 90 N/mm), the fuel pressure adjustment lags behind by 0.2 seconds, resulting in periodic “buzzing”. Data from the Mercedes-Benz C-Class Owners’ Forum show that these problems account for 23% of abnormal noise complaints.
Low-temperature and high-load environments increase the likelihood of abnormal noise. At ambient temperature lower than -10°C, Fuel viscosity rises from 0.75 mm²/s to 4.5 mm²/s, the Fuel Pump motor load current rises from 5A to 9A, the rate of carbon brush wear is boosted by 200%, and irregular “click” noises are produced. Volvo’s 2020 Arctic test showed that the probability of abnormal noise from the XC60’s fuel pump at -20°C cold start is four times higher than at ambient temperature. For turbocharged cars, at high levels of boost (e.g., 1.5 Bar), if the fuel pump flow is insufficient (less than 4 L/min), the fuel injection pulse width needs to be raised by 30%. The prolonged overload operation of the pump body makes the bearing temperature increase by over 120°C, and the noise decibel value rises by 3 dB for each 10°C rise.
Market solution verification technology optimization path. The fuel pump that suppresses noise (EVO-12S model) from Bosch, launched in 2023, uses polyamide resin impellers and ceramic bearings, reducing the friction coefficient to 0.03 from 0.15, decreasing noise by 40%, and extending the life cycle to 250,000 kilometers at the same time. User testing identifies that the model with this pump at idle speed has decreased its median noise by 38 dB to 28 dB, while the flow stability has been increased to ±3%. Statistics within the industry find that the abnormal fuel pump noise repair cost stands at $300 to $800. However, replacement over time can prevent associated losses such as clogging of fuel injectors (it costs more than $1,500 to repair it), and the ROI is 1:4.3.