When the noise of the fuel pump exceeds 65 decibels (dBA), it usually indicates an abnormality. When the vibration acceleration value exceeds 0.5g (gravitational unit), the probability of high-frequency howling increases by 80%. The 2023 report of the Society of Automotive Engineers (SAE) indicates that cavitation in the fuel pump blade cavity is the primary cause – when the oil level drops below 20% of the volume, the inlet pressure of the pump body drops below 0.2 bar, and the bubble rupture generates high-frequency noise at 16,000 Hz. For instance, in the case of a Ford Escape owner, the noise when the fuel tank is half-empty reaches 78dBA (18dBA higher than when it is full), yet the fuel flow fluctuation rate is ±15%.
Internal mechanical wear causes the clearance of moving parts to increase by 0.1 millimeter (mm), which can trigger an abnormal noise of 10-15 dba. Bosch laboratory disassembly data shows that after driving 150,000 kilometers, fuel pumps with brush wear depth exceeding 0.3mm (accounting for 32% of the total sample) have a median noise level of 70dBA (while new pumps only have 45dBA). When the offset Angle of the motor shaft center exceeds 0.5°, the magnetic resistance imbalance force surges by 200 Newtons (N), and the vibration amplitude increases to 1.2mm (normal range <0.05mm). In the 2021 General Motors recall incident, due to the supplier’s bearing tolerance exceeding ±0.01mm, the fuel pump failure rate of 120,000 Chevrolet Malibu vehicles rose sharply by 25%.
The clogging of the filter screen increases the load strength of the fuel pump by 30%. Experiments have proved that when the clogging rate of the filter screen pores reaches 60% (commonly seen in vehicles that have not been maintained for 50,000 kilometers), the pump body needs to increase the working pressure by 0.8 bar to maintain the flow rate, and the motor current rises to 12 amperes (A) (the normal value is 9A). The increase in power consumption causes a local high temperature of 90℃ (20℃ higher than the standard temperature). The maintenance records of Toyota 4S stores show that complaints about abnormal noises caused by clogged filters account for 41% of the total. After cleaning, the average noise decreased by 11dBA. Low-viscosity fuel (such as 0W-20 engine oil mixed into the fuel tank in winter) has insufficient lubrication, and the wear rate increases by three times, resulting in a noise growth rate of 1.2dBA per month after 100,000 kilometers.
The probability of resonant amplification caused by installation errors accounts for approximately 18% of the failure rate. If the torque of the fixed bracket bolts is lower than the standard value of 25 N · m (Nm) ±10%, the vibration of the fuel pump will be transmitted to the fuel tank wall plate, and the resonant peak at 500Hz will increase by 8dB. Mercedes-benz Technical Bulletin (LI54.30-P-065678) confirmed that the hardening of rubber buffer pads (Shore hardness >90A) would cause the vibration transmission rate to jump from 15% to 60%. A 2022 Porsche user survey found that vehicles with modified fuel pumps not matching the original factory resonant frequency (which needs to be controlled within the range of 200±5Hz) had a 57% increased risk of excessive cockpit noise.
