Fuel Pump noise increase is usually caused by component wear, abnormal system load or installation problems. When the Fuel Pump’s carbon brushes wear off by over 40% of the original thickness (standard thickness 3mm), the contact resistance between commutator and brushes rises from 0.1Ω to 0.6Ω, and the motor speed fluctuation rate is over ±10%, high-frequency howling with a frequency of 2-4kHz will be generated. The recall case of a certain German car company’s cars in 2020 revealed that, due to the fatigue of the impeller shaft sleeve material (the hardness dropped from HRC 60 to HRC 48), the fuel pump noise level rose from 55dB to 68dB. 72% of the noise sources in the faulty cars were found to be from the internal resonance of the pump body.
A clogged fuel filter is a common cause. Filter pressure difference exceeds 70 kpa (normal < 30 kpa), fuel flow 120 l/h down to 65 l/h, 5 a down to 9 a pump motor current, winding temperature rise to 125 ℃ (normal operating condition 90 ℃ or less), The evaporation rate of the bearing grease increases by 2.5 times, and the friction noise amplitude increases by 35%. Independent laboratory tests show that the degree of clogging of the filter element directly correlates with the decibel rating of the noise (R²=0.82). If the clogging area is greater than 50%, then the chance of the Fuel Pump generating excessive noise increases to 67%.
Cavitation noise may be due to installation defects. When Fuel Pump flange sealing ring compression is less than 30% of the design value (normal compression value is 1.2mm), there is fuel vapor leakage at a rate of 0.3L/min, with periodic cavitation noise at a frequency of 1.2kHz. The example of certain vehicle models’ maintenance shows that if the negative pressure in the Fuel tank is more than -4 kpa, the cavitation effect of the Fuel Pump impeller causes a flow fluctuation rate of ±15% (normal ±5%), and the noise peak is 12dB higher than the reference. Additionally, if the diameter tolerance of the impeller within a non-original fuel pump exceeds ±0.4mm (the original plant requirement ±0.1mm), the clearance deviation with the casing will reach 0.18mm (design value 0.05mm), and the possibility of abnormal noise will reach 65%.
The unstable voltage will worsen the noise. Arg, Pump depends on the 12 v + / – 10% power supply voltage, when wire resistance corrosion 1.5 Ω (normal 0.3 Ω) or less, actual power motors from 50 w down to 80 w The speed of rotation decreased from 3000rpm to 2100rpm. In this situation, the control module (FPCM) altered the PWM duty cycle at a frequency of 150Hz, which generated pulse noise. A part of the diagnostic data shows that when voltage fluctuation is over ±2V, the customer complaint rate of Fuel Pump noise is increased by 45%, and the standard deviation of the sound pressure level in the high-frequency range (>3kHz) is expanded 2.8 times.
The issue of oil product compatibility cannot be ignored. The Fuel with Methanol content (e.g., M15) can cause the swelling rate of plastic components in the Fuel Pump to be higher than 1.2% (volume change), which causes interference and friction between the impeller and the casing, and the noise energy is concentrated between the 1.6-2.0kHz frequency range. Brazilian market research shows that, in comparison to pure gasoline cars, the Fuel Pump noise failure rate in cars utilizing E27 ethanol gasoline is 31% greater. Moreover, when the axial clearance deviation caused by swelling exceeds 0.25mm, maintenance costs increase by 60%. Through cross-comparing vibration spectrum analysis (FFT peak >5g²/Hz) and the pressure sensor information, the noise source can be accurately located and the maintenance strategy optimized.