The sudden failure of the Fuel Pump is often manifested as the engine stalling without any warning during driving, which stems from the collapse of its core function – maintaining the base fuel pressure. Modern electronically controlled fuel injection systems require that the fuel rail pressure must be maintained within the range of 32 psi to 65 psi (depending on the engine design). When the internal circuits or mechanical components of the pump suddenly fail, the pressure can drop by 90% within 0.3 seconds. The 2020 report of the National Highway Traffic Safety Administration (NHTSA) of the United States analyzed 215 traffic accidents caused by fuel pump failures. Among them, 83% of the cases recorded that the engine speed dropped directly from 2500 rpm to 0 rpm before the engine was turned off. During this period, the air-fuel ratio sensor reading soared from 14.7:1 to over 18:1 within 0.5 seconds. It exceeded the ECU control limit value (±25%) by 47%.
Abnormal voltage supply is the primary cause of sudden pump death. The electronic fuel pump operates in the range of 9V to 16V. When the resistance value rises above 5Ω due to the corrosion of the wiring harness (the standard should be less than 0.5Ω), the actual working voltage may be lower than the critical value. Ford’s technical announcement for a large-scale recall of 670,000 vehicles in 2021 revealed that oxidation of the circuit terminals reduced the current transmission capacity by 35%, and the torque output of the fuel pump motor decreased, causing it to stop directly under load conditions below 1,800 RPM. Delphi’s laboratory reproduction tests show that the flow attenuation curve drops exponentially when the voltage is below 9.2V (the flow at 9V is only 31% of that at 12V), which is the physical essence of waiting for a red light to turn off at an intersection.
Thermal management failure also triggers sudden faults. The Fuel Pump assembly integrated in the fuel tank relies on fuel for cooling (the target temperature needs to be <85℃), and the heat dissipation capacity sharply decreases when the fuel volume is lower than 8 liters. Toyota’s technical service announcement T-SB-0046-21 confirmed that when driving continuously for 90 minutes in a low-fuel state combined with a high-temperature environment of 35℃, the pump body temperature can exceed the design limit (the standard peak temperature is 110℃, and the actual temperature reaches 142℃), and an irreversible demagnetization effect occurs in the internal permanent magnets. According to the 2019 data disclosed by the European Road Accident Research Association, the probability of thermal failure of fuel pumps in summer is 187% higher than that in winter, and engine stalling incidents within the last 3 kilometers of a gas station when the fuel tank is empty account for 28% of total failures.
There is a critical threshold for the mechanical wear of brush/commutator assemblies. When the thickness of the copper brush wears from the new standard 3.5mm to below 1.0mm, the spring tension drops by 60%, resulting in poor contact. According to the disassembly statistics of Bosch’s after-sales department, among the electric fuel pumps with a driving distance of over 150,000 kilometers, 69% of the samples had carbon powder deposits on the brushes (thickness >0.2mm), increasing the probability of sudden circuit breaks by 7 times. This situation is particularly dangerous during deceleration – Volkswagen MQB platform vehicles once experienced a sharp increase in stalling rate when the speed dropped from 60km/h to 20km/h. Due to the sudden change in deceleration torque, the motor load suddenly changed, and the wear point could not withstand a current transient of more than 8A.
The avalanche effect of physical blockage cannot be ignored. When 80% of the surface area of the filter screen is covered by particles (with a diameter >10μm), the flow rate can still maintain 65% of the design value. However, when the critical threshold is exceeded at a certain moment (such as 90% coverage), the flux will drop sharply by 40%. Chrysler’s warranty data analysis confirms that gasoline containing 20% ethanol will accelerate the separation of impurities. In vehicles with a mileage of 40,000 to 60,000 kilometers, 24% of the filter clogging rate exceeds the critical point. In 2022, the U.S. Environmental Protection Agency’s road tests recorded that such congestion caused the fuel pressure to plummet from 45psi to 12psi in just 1.2 seconds, which was sufficient to trigger the ECU’s forced shutdown protection mechanism (fault code P0087).
Therefore, a sudden engine shutdown is like a “dying electrocardiogram” of a fuel pump, indicating not only the collapse of key power supply/cooling functions but also revealing that mechanical structural fatigue has reached a critical point. For vehicles that are over 6 years old or have traveled 100,000 kilometers, an oil pressure test should be conducted immediately upon the appearance of this symptom (a diagnosis can be made if the pressure at idle is 20% lower than the rated value) to avoid the risk of power interruption during high-speed driving. Industry statistics show that in cases of sudden engine stalling repair, 38% of the cases returned to normal immediately after the fuel pump was replaced, which is nearly three times higher than the 10% diagnosis rate of other system failures.