Approximately 60% of fuel pump failures result from brush wear (failure occurs when the measured value is less than 0.8mm). At this point, the carbon brush assembly (costing 30 yuan) can be replaced to restore the function, with a success rate of 85%. For instance, in the 2023 Volkswagen Golf maintenance case, the original pump brush thickness wore from 4mm to 0.5mm. After replacement, the flow rate recovered to 4.5L/min (standard value ±0.2L/min), and the vibration amplitude dropped to 0.05mm. However, if the motor coil is short-circuited (impedance value <1Ω), the repair cost will exceed 80% of the price of a new pump, and there is a 50% secondary failure rate. Industry standards suggest direct scrapping.
Filter screen clogging accounts for 35% of repairable faults. When the pore clogging rate is greater than 70% (with a normal permeability area of 380mm²), cleaning can increase the flow efficiency by 92%. Measured data: After the fuel pump filter of the Honda Civic was cleaned, the working pressure recovered from 1.8 bar to 3.2 bar (tolerance ±0.1 bar), and the current value dropped to 6 amperes (original value 9A). It needs to be treated with an ultrasonic cleaner (with a frequency of 40kHz) for 15 minutes. The particle size of the residual particles should be less than 10μm (equivalent to 1/8 the diameter of a human hair), otherwise the impeller gap may be scratched (the allowable tolerance is only 0.02mm).
Irreparable scenarios: Aging of the sealing ring (compression permanent deformation rate >30%) or cracks in the pump casing (length >0.3mm). The BMW Technical Bulletin (SI B13 07 22) pointed out that the pressure attenuation rate caused by shell leakage is 0.2 bar per minute. Even if it is repaired by welding, it is difficult to reach the original factory sealing standard (helium leakage detection rate <10⁻⁶ mbar·L/s). In the 2021 Ford Kuga recall incident, due to the third-party repair of the fuel pump housing, the probability of the fuel vapor leakage concentration reaching the lower explosive limit (1.4%) increased by 12 times, and the risk of triggering the ECU error P0455 increased by 40%.
Economic analysis: For high-end vehicle fuel pumps (such as the Mercedes-Benz S-Class), if the price exceeds 4,000 yuan, the repair budget is less than 1,000 yuan and the expected lifespan reaches 80% of the new part (approximately 40,000 kilometers), then it is feasible. The Audi A6 maintenance case shows that replacing the bearing (at a cost of 200 yuan) reduced the noise from 78dBA to 45dBA. However, if the cumulative mileage exceeds 200,000 kilometers, the mean time between failures (MTBF) after the repair is only 5,000 hours (35,000 hours for new parts), which means that the probability of re-damage after 9 months is 65%.
Ultimate Decision Tree
Repairable: Brush wear (New brush cost < 20% of new pump)/Filter screen clogging (cleaning time < 45 minutes)
To be scrapped: shell damage/seal failure/coil abnormality (maintenance cost > 70% of the new pump)