Among the cases where fuel leakage occurs at the flange of the fuel pump, 47% are due to the failure of the sealing system. When the compression rate of the sealing ring is 30%±5% lower than the design standard (for example, the original factory requires 3.0mm to be compressed to 2.1mm), the leakage probability rises to 65% under an oil pressure of 350kPa. The recall incident of Tesla Model S in 2020 confirmed that the hardness error of the fluororubber seals provided by the supplier exceeded ±5 Shore A (standard 70±3), resulting in a permanent deformation rate of 38% after 100,000 kilometers and an average leakage rate of 5 milliliters per minute.
The installation process error accounts for 33%. If the torque of the flange bolts does not reach 8N·m±0.5N·m (for example, only 5N·m is applied), the pressure distribution on the sealing surface is uneven, and the local gap exceeds 0.1mm, causing leakage. BMW’s technical bulletin SI B16 03 19 pointed out that among 2,000 rework samples, 63% suffered a 40% loss in the effective compression of the sealing ring due to the failure to clean the sealing surface (residual particle diameter > 30μm). The measured results show that dust embedding will expand the leakage cross-sectional area to 0.8mm², far exceeding the safety threshold of 0.05mm² stipulated in SAE J1645.
Material compatibility issues account for 12%. Ethanol gasoline (E20 and above) raises the swelling rate of nitrile rubber to 15% (the upper limit of the standard is 8%), and the volume expansion leads to a 50% attenuation of sealing stress. Maintenance data of the Ford Flex model shows that after using alcohol-based fuel for three years, the hardness of the seal decreased from 70 IRHD to 55 IRHD, and the fuel permeability increased by 300%. Fluorosilicone rubber seals that comply with the ISO 1817 standard can control the expansion rate within ±3%, but the cost increases by 200%.
The risk of structural deformation accounts for 8%. The coefficient of thermal expansion of aluminum alloy flanges reaches 23×10⁻⁶/℃ at an oil temperature of 120℃. If the deviation of the fastening force distribution exceeds 15%, it will lead to a flatness error of more than 0.2mm/m. Test data of the Porsche 991.2 GT3 show that the flange temperature difference under track conditions reaches 80℃, and the uneven deformation causes the local sealing pressure to decay to 0.8MPa (the design value is 1.5MPa). The solution is to adopt reinforced composite material brackets to control the deformation within ±0.05mm.
Leakage diagnosis requires three-dimensional detection: Use a feeler gauge with an accuracy of 0.05mm to measure the flange gap (threshold 0.03mm); Leakage rate detected by helium mass spectrometer (standard < 1×10⁻⁶ mbar·L/s); Thermal imagers capture high-risk areas where the temperature difference is greater than 10℃. Preventive maintenance in compliance with the ISO 14224 standard reduces the failure rate by 90%, and the cost of a single repair drops from 450 to 80. The maintenance of the original Fuel Pump includes laser-etched positioning gaskets, and the installation qualification rate reaches 99.8%.