The probability of engine misfire caused by fuel pump failure is as high as 74%. Due to insufficient pressure (<45 PSI), the air-fuel ratio deviates from the ideal value by ±10% (under normal conditions, it needs to be maintained at 55-65 PSI). Actual measurements show that when the flow rate drops by 18% (such as from the original factory pump design of 60 L/h to 49 L/h), the frequency of misfire at high RPM above 2000 increases to 42% (SAE 2023 study: The correlation degree r of the trigger rate of fault code P0300 on 12 test vehicles is 0.88). A typical case is the Fiat recall incident in 2019 (NHTSA 19V-100), where 150,000 vehicles experienced pressure fluctuations of ±8 PSI due to wear of the fuel pump impeller, with a fire rate of 39% under specific working conditions.
The performance deterioration of Fuel Pump has progressive characteristics: Initially, it is manifested as the rate of oil pressure drop >0.5 PSI/ second (ISO 4020 diagnostic standard), causing intermittent misfire (duration <100ms); When the late flow rate drops to 60% of the threshold, the misfire frequency across the entire rotational speed range exceeds 15 times per minute. Deloitte’s “Automotive Failure Analysis Report” quantified that a 0.2-millimeter wear of the impeller (accounting for 10% of the thickness) led to an 8% decline in flow rate. Coupled with circuit aging (resistance deviation exceeding ±0.3Ω), the motor speed fluctuated by ±18%, ultimately resulting in the failure of ECU correction (air-fuel ratio deviation >±2.0).
The risk of intensified coupling between temperature and operating conditions: When the ambient temperature exceeds 38℃, the heat dissipation efficiency of the faulty pump drops by 22%, the coil temperature rise rate reaches 1.1℃/ second (compared with 0.3℃/ second for the new pump), and the probability of thermal protection triggering increases by 33%. For instance, in the 2022 Australian truck accident survey (sample n=78), 68% of the cases of engine misfire caused by pump failure at high temperatures led to brake failure. The distribution of misfire in multiple cylinders is also characteristic – fuel pump failures usually affect high-load cylinders (such as Cylinder 3 and Cylinder 4) first, and the increment of the misfire counter accounts for more than 65% (OBD-II data cluster analysis).
The economic impact is significant: A single fire incident may damage the three-way catalytic converter (with a repair cost of 640 yuan), while the total cost of replacing the oil pump is only 220 yuan. The return on investment loss due to delayed repair amounts to 191% (based on a two-year life cycle). The active monitoring strategy includes real-time reading of the oil rail pressure sensor (target error <±0.8%), and the failure probability is >92% when the pressure value at 2000 RPM is <42 PSI. The recommended preventive replacement cycle is 8 years / 150,000 kilometers (based on the Weibull failure model η=7.2), which can reduce the risk of misfire by 76% (validation data from SAE Paper 2021-01-5054).
(Failure critical point verification: When the pressure oscillation amplitude is greater than ±4 PSI and the frequency is greater than 5Hz, the failure probability of the fuel injection pulse width control is 87%) Diagnostic priority ranking: The fuel pump problem should be ruled out first, and then the ignition system should be checked (EPC analysis shows that the efficiency has increased by 40%). The final disposal requires measuring the pressure retention value after engine shutdown (normal >35 PSI for 10 minutes). If it is less than 25 PSI, it is confirmed that the pump body is leaking (Delphi maintenance manual standard procedure).