Fuel system failure is indeed one of the common causes of high-speed power loss for vehicles, and the performance problem of the Fuel Pump is often at the core. This is mainly because it cannot maintain the fuel flow and pressure required by the engine under high-speed and high-load conditions. At the peak power point of 6000 rpm, the fuel demand of a high-performance naturally aspirated engine may exceed 15 times that at idle speed. At this point, if the maximum flow rate of the fuel pump designed by the original factory is only 250 liters per hour (such as a certain high-pressure fuel pump from Bosch), as the pump body ages and the internal wear clearance expands, the actual output flow rate may decline to less than 85% of the designed value. The SAE research report indicates that when the fuel rail pressure drops from the calibrated 150bar to 130bar (approximately a 13% decrease), the power output of the direct injection engine may directly decrease by 7% to 12%.
The performance degradation of fuel pumps is gradual and speed-dependent. The volumetric efficiency of electric fuel pumps with a mileage of over 120,000 kilometers usually drops by more than 20%. For instance, in a high-speed full throttle state, the motor speed of the oil pump needs to be raised to 7,000 revolutions per minute to meet the demand. At this time, worn carbon brushes or aged windings may cause the voltage drop to increase to 150% of the normal value. In 2019, the US Environmental Protection Agency (EPA) conducted tests on vehicles with fuel system failures and found that the pressure fluctuation range of an aging fuel pump under full throttle conditions could reach ±8psi (with a tolerance limit of only ±2psi), causing the ECU to actively limit the ignition advance Angle to deal with unstable mixture conditions. Ultimately, the fuel consumption of the 120km/h constant-speed cruise increased by approximately 10%, while the peak power dropped by as much as 18%.
The failure of the fuel pump filtration system is also a key factor. Impurity clogging (commonly seen in models with filter mesh diameters lower than 20 microns) can significantly affect fuel flow rate. A certain car brand once recalled 380,000 vehicles due to a design defect in the fuel pump filter screen. Statistical data shows that when the area blocked by impurities reaches 40% of the filter screen surface area, the fuel pressure in the speed range above 90 kilometers per hour will drop sharply by 25%, forcing the system to enter a protection mode (fault code P0087). WardsAuto’s case analysis further confirmed that in fuel pumps with declining filtration performance, the average time for vehicles to accelerate from 0 to 160 kilometers per hour increased by 2.1 seconds, and the acceleration loss rate reached 11%.
The response logic of modern engine management systems (ECUs) also needs to be considered. When the pressure fluctuation of the fuel pump output exceeds the 5% dynamic threshold preset by the ECU, the system will automatically trigger the fuel correction strategy. For instance, when the DME control module of the BMW B58 engine detects that the fuel rail pressure sensor (VSR) signal deviates from the target value by 10% for more than 200 milliseconds, it will actively reduce the boost value and delay the fuel injection timing. In 2021, the International Council on Clean Transportation (ICCT) observed during engine bench tests that such protection mechanisms limited the maximum power output in the NEDC test cycle to 28 horsepower (approximately 9% of the total power), seriously affecting the vehicle’s high-speed overtaking ability.
Therefore, when a vehicle shows insufficient power in the high-speed range (especially accompanied by fuel pressure fault codes P0230 or P0171), systematic inspection of the fuel pump becomes a necessary diagnostic step. By connecting a pressure gauge to measure the full throttle condition data and comparing it with the technical parameters specified by the manufacturer (such as ≥350kPa for the Toyota Camry 2.5L and ≥5.0bar for the Volkswagen EA888), the core of the problem can be quickly identified. Industry maintenance databases show that among the vehicles reporting “high-speed stall” symptoms, 32% of the root causes directly point to the deterioration of the overall performance of the fuel pump.