When the Fuel Pump fails to provide sufficient fuel flow, the system oil pressure usually drops below 70% of the standard value (for example, the common reference pressure of passenger vehicles, which is 300-400 kPa, drops to 200 kPa). At this point, the engine ECU detects through the oxygen sensor that the air-fuel ratio is too thin (higher than the theoretical value of 14.7:1), and forcibly extends the fuel injection pulse width to compensate for the fuel supply volume. Experimental data confirm that for every 50 kPa decrease in pressure, the fuel injection time increases by 0.3 milliseconds, causing an instantaneous 12% rise in fuel consumption. According to the statistics of the North American Society of Automobile Maintenance (ASA) in 2021, in cases of engine failure caused by insufficient fuel supply, the average fuel consumption of about 67% of vehicles increased by more than 15%. A typical phenomenon is that the fuel consumption of the 2.5L model of Toyota Camry deteriorated from 6.2L/100km to 7.4L/100km when cruising at 80km/h.
Insufficient fuel supply leads to an uneven distribution of the mixture concentration, causing the local combustion temperature to exceed 950℃, which is much higher than the normal operating condition threshold of 850℃. High temperatures have caused nitrogen oxide (NOx) emissions to soar by 250%, simultaneously triggering detonation sensor alerts at a frequency of over 15 times per minute. The Bosch engineering team found during bench tests that when the actual flow rate of the oil pump was 20% lower than the rated value (for example, from the original design of 60L/h to 48L/h), the probability of cylinder misfire increased by 150%. If this working condition persists for 30 minutes, the temperature of the spark plug electrode will exceed the safety limit of 1100℃, the ablation rate of the electrode gap will increase by three times, and the service life will sharply decrease from 60,000 kilometers to 20,000 kilometers.
Insufficient flow in the high-pressure oil circuit can also cause the oil pump motor to operate under continuous overload. In typical cases of rotor wear, the motor current rises to 130% of the standard value (about 6A), and the winding temperature exceeds 180℃ within 15 minutes, causing the insulation layer to carbonize and fall off. The German TUV certification report indicates that continuous low-pressure operating conditions have reduced the oil pump’s lifespan from an average of 8 years to less than 3 years. Meanwhile, the failure rate curve shows a sharp upward turning point in the 18th month, with the Weibull distribution shape parameter β value increasing from 1.8 to 3.5. In 2019, a certain online car-hailing company tracked 300 Honda Accord vehicles and found that the fuel pump replacement rate of vehicles with insufficient fuel supply was 43% ahead of schedule, and the cumulative maintenance cost exceeded 180,000 yuan.
The most dangerous consequence of a shortage of fuel flow is a sudden and unstable change in power output. When the system oil pressure drops sharply by 30% (for example, the pressure required for rapid acceleration is 400kPa but only 280kPa), turbocharged models will experience a torque drop within 0.5 seconds. The VTI Institute for Traffic Safety in Sweden analyzed highway accidents from 2018 to 2020 and confirmed that insufficient fuel supply led to 38% of sudden stall incidents, among which 65% occurred in the range of speeds above 100km/h. A typical case is that when the engine of the BMW N20 encounters a flow limit at 5000rpm, its power output drops sharply from 180kW to 95kW. The vehicle’s acceleration time from 60 to 100km/h is extended by 2.3 seconds, and the probability of overtaking failure increases by 90%. Therefore, regularly testing the Fuel Pump flow parameters (it is recommended to test the actual fuel supply rate attenuation every 30,000 kilometers) can avoid 96% of driving safety hazards, and the diagnostic cost only accounts for 5% of the parts replacement cost.