Fuel Pump pressure failure usually occurs through internal leakage or wear of components. According to SAE J2719 standard, the fuel pump pressure at the speed of idling should be stable between 3.0-4.5 bar. When the pressure fluctuation is greater than ±0.8 bar, the leakage may be up to 15 L/h (liters/hour) due to the aging process of the sealing ring. For instance, statistics by the North American Automobile Association (NADA) in 2023 show that out of all the vehicles whose mileage is above 80,000 kilometers, 38% of Fuel pump pressure attenuation result from nitrile rubber sealing ring hardening. The cost of replacement, on average, is $450, a rise of 72% compared to the failure of new pumps.
Contamination of fuel is yet another major reason. Above 50 mg/L particulate matter level in gasoline, the wear rate of Fuel Pump impeller is doubled to 300% causing the reduction in flow rate from 300 L/h to 190 L/h and pressure fluctuation range to ±1.5 bar. In the Volkswagen EA888 engine recall of 2022, due to low-quality gasoline at gas stations which clogs the filter screen (with pore size being reduced from 10 μm to 5 μm), error rate in the fuel pressure sensor rose by 21%, and repair cost for a single incident was over 600 US dollars.
Unstable voltage will further aggravate pressure loss control. The operating efficiency of Fuel Pump motor is 85% at a voltage of 12V. When the motor speed is lowered from 3000 rpm to 2400 rpm and the voltage is lowered to 10V, the pressure output decreases by 22%. Red Bull Racing Team in 2023 tested that the poor contact of the circuit (with an increase in resistance of 0.5Ω) caused a ±1.2V voltage fluctuation in the Fuel Pump. When subjected to severe load in the engine, pressure decreased sharply from 4.2 bar to 2.8 bar, air-fuel ratio deviation expanded from ±0.3 to ±1.5, and danger of overheating for catalytic converter increased by 55%.
Cavitation (Cavitation) causes slight damages. When the Fuel pipeline pressure is lower than that of the vapor pressure of the oil product (for instance, E85 ethanol fuel’s vapor pressure is 48 kPa when the temperature is 40°C), there will be formation of cavitation bursts on the Fuel Pump impeller surface that creates instantaneous high temperature (peak 150°C) and shock waves (pressure amplitude ±20 MPa). Bosch lab statistics show that cavitation can reduce the aluminum alloy impeller thickness from 3.0mm to 2.2mm for each 10,000 kilometers, and the pressure leakage rate will increase from 0.5L /h to 4.8L /h. With the Porsche 911 GT3 being modified to the high-pressure fuel rail (6 bar) in 2024, the incidence of cavitation failure fell from 7.3% to zero.
The strategy of maintenance has a bearing on the ability to maintain pressure. Among the cars in which the Fuel filter is never replaced at regular intervals (24,000 kilometers), the rate of failure of the Fuel Pump for overload conditions reaches 29%, while that of adequate periodic maintenance of the car is merely 3%. According to a 2024 study released in Automotive Engineering, Synthetic material-sealed fuel pumps (such as AEM 320LPH) suffered pressure loss of only 0.03 bar/ 1,000 kilometers in a 100,000-kilometer test, improving stability by 75% compared to traditional pumps (0.12 bar/ 1,000 kilometers) and reducing the average annual maintenance cost by $180.