Fuel Pump high-frequency noise is usually related to component wear, incorrect lubrication or unusual loading of the system. For example, when the carbon brushes of the Fuel Pump motor wear down over 50% of their original thickness (standard thickness is 3mm), the contact resistance between the brush and the commutator increases from 0.1Ω to 0.5Ω, causing the motor speed deviation rate over ±8% and generating a howling sound at a frequency of 2-4kHz. The situation of the 2022 recall of some vehicle manufacturer illustrated that due to the wear of impeller shaft sleeve material (down from HRC 58 to HRC 45), the fuel pump noise level of 120,000 vehicles rose to 65dB during idle speed (normal specification ≤55dB), and in 87% of defective vehicles, the sounds were originated inside the pump body.
The Fuel filter plugging will increase the Fuel Pump load and cause it to be noisy. Experiments show that when the filter element pressure difference exceeds 80kPa (normal value ≤30kPa), the fuel flow rate drops from 120L/h to 60L/h, the pump motor current rises from 5A to 9A, and the winding temperature rises to 130℃ (normal operating condition ≤90℃), resulting in three times the evaporation rate of the bearing grease and a 40% increase in the friction noise amplitude. Data from a specific maintenance chain indicate that out of vehicles with over 80,000 kilometers of mileage, Fuel pump noise complaint rate with prematurely replaced filter elements accounts for 63% of total faults, and noise duration is positively correlated with filter element blocking level (R²=0.78).
Faulty installation or component deformation can also produce abnormal noises. If the compression amount of Fuel Pump flange sealing ring is less than 30% of design value (the standard compression amount is 1.2mm), the fuel vapor will leak 0.2L/min, causing cavitation and creating periodic sound at a frequency of 1.5kHz. Experimental data in a given laboratory show that after the Fuel tank’s negative pressure is higher than -5 kpa, the cavitation effect of the Fuel Pump’s impeller results in the rate of flow fluctuation reaching ±12%, and the noise decibel value increases 15% above the standard condition. Also, if the diameter tolerance of the non-factory Fuel Pump’s impeller is bigger than ±0.3mm (the original standard of factory is ±0.1mm), the clearance deviation from the casing is 0.15mm (the design value is 0.05mm), and the probability of abnormal noise is up to 72%.
Abnormal voltage is also one of the critical causes. The Fuel Pump is designed based on a stable power supply with the voltage of 12V±10%. When the wiring harness resistance grows to 1.2Ω (normal ≤0.3Ω) due to corrosion, the motor actual power reduces to 55W from 80W, and the speed drops to 2200rpm from 3000rpm. Here, the control module (FPCM) dynamically adjusts the PWM duty cycle with a rate of 120Hz. Generate discernible pulse noise. The diagnostic data of the vehicle model shows that with the voltage variation beyond ±1.5V, the Fuel Pump complaint rate for noise is raised by 41%, and the standard deviation of sound pressure level of high-frequency band (> 3kHz) is raised by 2.3 times.
Incompatibility of oil products cannot be ruled out either. Methanol fuel (e.g., M15) can result in more than 0.8% (volume expansion) swelling rate of plastic components inside the Fuel Pump, which results in interference and abrasion between the impeller and casing, and noise energy is concentrated in the frequency band of 1.8-2.2kHz. Brazil market research shows that of vehicles operating on E27 ethanol gasoline, the Fuel Pump noise failure rate is 29% higher compared to pure gasoline vehicles. Additionally, if axial clearance deviation resulting from swelling deformation exceeds 0.2mm, maintenance and replacement costs are 55% greater. Through cross-verifying vibration spectrum analysis (FFT peak > 4g²/Hz) and pressure sensor readings, one can accurately determine the source of the noise and intervention strategies can be formulated.