In the Fuel Pump system, the design of the return oil pipeline is used to regulate the fuel pressure and ensure that the excess fuel returns to the fuel tank. If the return oil pipeline is artificially blocked, it may cause the system pressure to rise sharply to 2 to 3 times the original design value (for example, soaring from the standard 0.3-0.5 MPa to over 1.0 MPa), far exceeding the pressure resistance limit of the fuel Injector (usually 0.8-1.2 MPa). Take the recall incident of a certain German car brand in 2021 as an example. Some of its models had abnormal pressure due to design flaws in the return fuel valve, which led to a 47% increase in the failure rate of the fuel pump and an average repair cost of 1,200 US dollars per vehicle. Research data shows that when the return oil flow rate drops from the normal value of 5-10 L/min to 0, the load current of the fuel pump motor will increase by 30% to 50% (for example, from 4A to 6A), causing the motor temperature to rise by more than 80°C (40-60°C under normal working conditions), significantly shortening its service life (from the designed life of 100,000 hours to less than 60,000 hours).
From a thermodynamic perspective, blocking the return oil pipeline will change the thermal equilibrium state of the fuel system. Experimental data shows that under an ambient temperature of 25°C, the heat dissipation efficiency of the fuel circulation decreases by approximately 65% (from 70% of the system heat carried away by the return fuel to 25%), causing the fuel temperature to rise at a rate of 1.5-2.0°C per minute. When the fuel temperature exceeds 60°C, its viscosity decreases by 40% (from 0.8 mm²/s to 0.48 mm²/s), which will directly affect the injection accuracy (the error rate expands from ±1.5% to ±3.8%). Taking the actual test of a certain American pickup truck model as an example, after 30 minutes of continuous high-load operation, the fuel temperature rose from the reference value of 45°C to 72° C. Meanwhile, the volumetric efficiency of the fuel pump dropped from 92% to 78%, and the fuel economy deteriorated by 15%.
From the perspective of safety, statistics from the National Highway Traffic Safety Administration (NHTSA) of the United States show that approximately 18% of traffic accidents involving Fuel Pump failures are related to abnormalities in the pressure regulation system. When the return oil pipeline is completely blocked, the system pressure fluctuation range expands to three times the designed value (for example, from ±0.05 MPa to ±0.15 MPa), which will cause the measurement error rate of the pressure sensor to increase sharply from 1% to 5%. In extreme cases, the pressure peak may exceed the mechanical strength limit of the fuel pipeline joint (typically 2.5-3.0 MPa), resulting in a 300% increase in the risk of leakage. In a case in 2019 where a Japanese hybrid model accidentally sealed the fuel return pipe during maintenance, causing a fuel leak and resulting in a fire, the insurance company determined that the loss from a single accident was as high as 23,000 US dollars, far exceeding 50 times the normal maintenance cost.
Industry solutions show that the design of replacing fixed return oil pipes with dynamic pressure regulating valves can increase system energy efficiency by 12-15%. For example, Bosch’s third-generation high-pressure Fuel Pump improves the pressure regulation accuracy to ±0.02 MPa by integrating an electronic pressure control module, while reducing mechanical wear by 30%. Test data show that under the same working conditions, the fuel pump life of the intelligent regulation system has been extended to 150,000 hours (a 50% increase compared to the traditional design), and the time between failures (MTBF) has been increased from 8,000 hours to 12,000 hours. This technological innovation has reduced the maintenance cost of the vehicle’s fuel system by 40%, meeting the strict requirements for the reliability of automotive electronic equipment in the ISO 16750-2 standard.