The occurrence of backfire in internal combustion engines is significantly correlated with abnormal fuel pump pressure. Research shows that when the output pressure of the fuel pump is lower than the standard value of 2.5 PSI (pounds per square inch), the air-fuel ratio error of the mixture will exceed ±3%, causing unburned fuel to enter the exhaust system. In 2019, test data from the Society of Automotive Engineers (SAE) of the United States showed that among 200 vehicles with backfire faults, 43% had problems with fuel pump flow attenuation, with 72% of the pump body flow being lower than the manufacturer’s rated value of 0.8 L/min (liters/minutes). For instance, a recall incident of a certain German car model revealed that due to the oil pump pressure fluctuation reaching ±4% (exceeding the allowable range of ±1.5%), the exhaust temperature suddenly rose to 650℃, causing the frequency of backfire to increase by 300%.
The voltage stability of the fuel pump directly affects the accuracy of fuel delivery. When the voltage fluctuation exceeds ±0.5V, the power output deviation of the pump body can reach 15%, resulting in a reduction of more than 20% in the instantaneous oil supply. The 2022 European Accident Database (EEAD) indicates that periodic pressure loss caused by poor circuit contact can increase the probability of backfire by 18 times. In a specific case, when a racing car was accelerating in a corner, due to the fuel pump voltage dropping to 10.8V (standard 13.5V±0.2V), the instantaneous fuel cut-off at 6000rpm triggered an exhaust pipe explosion, with the flame length reaching 1.2 meters, verifying the causal relationship between fuel supply interruption and backfire.
The attenuation of oil pump life is a potential cause of progressive tempering. When the carbon brushes of the pump body motor wear more than 50% of their original thickness, their power efficiency will drop from 92% to 78%. Actual data shows that the average flow rate of the fuel pump in a vehicle that has traveled 100,000 kilometers drops by 17.5%. At this point, the variance of the mixture concentration fluctuation reaches 0.8 (0.3 for a new car), causing the frequency of low-speed backheat to soar from 0.3 times per month to 5.2 times. Ford’s 2021 technical circular confirmed that in tropical climate regions, the service life of fuel pumps due to high-temperature aging was shortened to four years, a 33% reduction compared to temperate regions, and the corresponding vehicle backfire complaint rate was 230% higher.
Diagnosing tempering faults requires a comprehensive assessment of the pump body parameters. Monitoring with a pressure sensor revealed that a sudden drop in fuel pressure often occurred 300ms before tempering, with the typical value dropping from 45PSI to 28PSI±3PSI. Mercedes-benz’s maintenance guidelines released in 2023 stipulate that if a flow accuracy deviation of ≥±5% or a pressure amplitude exceeding ±2PSI is detected, the Fuel Pump must be replaced immediately. In actual cases, a modification shop in California upgraded the oil pumps of 50 tempered vehicles (increasing the flow rate from 150L/h to 255L/h), successfully raising the elimination rate of abnormal exhaust noise to 98% and reducing maintenance costs by 40%, verifying the effectiveness of the systematic solution.