Fuel Pump performance degradation can have a significant impact on fuel economy. When the Fuel Pump’s fuel supply pressure drops from its normal value of 3.5bar to 2.8bar, the ECU will compensate the air-fuel ratio by increasing the fuel injection pulse width (from 3.5ms to 4.2ms), leading to an increase in fuel consumption by 7%-12% per 100 kilometers. For instance, in 2021, one German automaker recalled 90,000 cars due to Fuel Pump impeller design flaws. Data shows that the fuel efficiency of flawed cars increased by 1.2L/100km on average, and the loss in fuel efficiency amounted to an additional annual expense of 180 * * (calculated based on an annual driving distance of 20,000 kilometers and an oil price of * * 1.5/L).
The other key parameter is the poor traffic. When the maximum flow rate of the Fuel Pump deteriorates from 120L/h to 90L/h, the fuel supply response under the high-load condition of the engine is delayed by 0.3 seconds, and the ECU is forced to enter the “limping mode” and enrich the mixture (the λ value drops from 1.0 to 0.85). The maximum instant fuel consumption can reach 18L/100km (normal 12L/100km). An independent test shows that after the steady climb of a 10-kilometer gradient, the fuel consumption of the worn Fuel Pump was 15% higher than that of the new pump, and the hydrocarbon emissions were 22% higher.
The decrease in efficiency of the Fuel Pump motor has the immediate result of increasing energy consumption. When the carbon brushes are worn, causing the motor efficiency to drop from 85% to 70%, the power consumption rises from 60W to 75W, equivalent to the consumption of an additional 0.6L of fuel for every 1,000 kilometers of travel (calculated based on a generator conversion efficiency of 80%). Comparative lab data shows that the use of brushless motor Fuel pumps (e.g., Denso 950-0115) can enhance energy efficiency by 18%, reduce fuel consumption by 0.5L per 100 kilometers, and save 375 * * (oil price * * 1.5/L) in fuel costs over a 50,000-kilometer lifespan.
Fuel consumption is aggravated by the interaction of oil contamination and Fuel Pump. Fuel with gum (gum content >7mg/100mL) will increase the blocking rate of the filter screen pore by 40%. As soon as the pump body load increases, the fuel reflux rate from 5% to 12%, the reduction of the effective fuel supply makes the ECU correction times increase by 30%. Market tests in Brazil show that vehicles fueled with E25 ethanol gasoline have 4.3% higher Fuel consumption on average than pure gasoline vehicles due to Fuel Pump intake valve corrosion (leakage >8mL/min), with the failure rate increasing exponentially with distance (R²=0.91).
System matching level also matters. Modifying high-flow Fuel pumps (e.g., Walbro 255L/h) without changing the fuel injectors simultaneously, the excess fuel supply will cause a 9%-15% loss in fuel utilization rate. In a track test, the unmatched Fuel Pump caused the vehicle to consume an additional 28 liters of fuel in the 400-kilometer endurance competition and increased the standard deviation of lap stability by 1.2 seconds. On the contrary, with the utilization of dynamic pressure regulating technologies (i.e., Bosch EFP3), it is possible to maintain the fuel flow error rate within ±2%, the comprehensive fuel-saving effect can reach a maximum of 3.8%, and the return on investment period is less than 2 years (calculating with the yearly driving mileage of 15,000 kilometers). By monitoring in real time the operating parameters of the Fuel Pump (e.g., pressure sensor drift >±0.5bar), maintenance can be intervened in advance to avert the surreptitious increase in fuel costs.