The performance degradation of the fuel pump can lead to lean combustion (air-fuel ratio >14.7:1), and the core mechanism is insufficient fuel supply pressure. Experimental data confirm that when the pump output pressure is 30% lower than the nominal value (for example, the standard 60 psi drops to 42 psi), the fuel flow error reaches ±15%, triggering the risk of ECU fuel injection compensation failure. In 2020, the SAE research report analyzed 500 cases of lean-burn faults, among which 27% of the root causes were Fuel Pump failures. This was manifested as a pressure sensor reading fluctuation of more than ±5 psi, and the probability of the oxygen sensor voltage remaining continuously below 0.45V increased by 80%, directly causing the frequency of the P0171 fault code to rise by 62%.
The quantified indicators of mechanical wear directly affect the failure rate. When the brush wear exceeds 0.8mm or the rotor clearance expands to 0.15mm (the design limit is 0.05mm), the annual flow rate attenuation can be as high as 12%. Take the Honda recall incident in 2016 as an example. The deformation probability of the material strength defect of its impeller at 80°C was 38%, and the flow rate dropped sharply from 55 GPH to 40 GPH, causing the air-fuel ratio deviation of 120,000 models to exceed +2.0 and the NOx emission concentration to exceed the limit by 30 ppm (the EPA limit is 30 ppm). This incident caused the enterprise a loss of $22 million in maintenance costs, confirming that for every 10% decrease in pump flow rate, the concentration of the mixture in the cylinder decreases by 8.5%.
Voltage disturbances exacerbate abnormal fuel supply. Tests show that when the system voltage drops to 11.5V, the motor speed decays by 15% and the pressure output decreases by 20%. The 2022 Ford F-150 Owners’ Forum statistics confirmed that when the line impedance is greater than 0.3Ω, it causes a voltage drop of 12%, and when the pump load current is overloaded to 15A (rated 13A), the probability of inducing lean-burn is 3.2 times higher than that of the normal group. Advanced solutions such as Delphi’s intelligent pump module employ the PID algorithm to converge pressure error to ±0.8 psi, reducing the leor-burn rate by 65% and saving maintenance costs by $180 per vehicle trip.
Preventive strategies rely on precise monitoring cycles. Life cycle assessment indicates that the pump pressure attenuation rate needs to be detected every 50,000 kilometers. If the pressure value drops below 90% of the peak after 100,000 start-stop cycles (for example, 55 psi→49.5 psi), the failure probability exceeds 40%. The NHTSA accident database (2018-2023) reveals that 71% of traffic accidents caused by Fuel Pump failure are related to lean combustion stall. Industry standards recommend an 8-year or 120,000-mile replacement cycle. This solution can reduce risks by 85% and simultaneously lower CO emission concentrations by 15 ppm, meeting the EU Euro 6d emission standard limit requirements.