The cold start performance is closely related to the low-temperature characteristics of the Fuel Pump. When the ambient temperature drops to 0℃, the viscosity of gasoline increases by 37%. This requires that the fuel pump motor output torque at 12V voltage be at least 15% higher than at normal temperature to maintain the rated flow rate. Bosch Laboratory tests in 2021 showed that the peak starting current of the aged fuel pump decreased by 22% at -5℃ (from 7.3A to 5.7A), causing the fuel pressure build-up time to be extended from the standard value of 1.8 seconds to 3.5 seconds. At this point, the long-term fuel correction value recorded by the ECU can abnormally soar to +28%, increasing the probability of ignition failure in the first cycle by 64%. This is a typical cause of difficulty in starting in the early winter morning.
Electrochemical corrosion significantly weakens low-temperature performance. For fuel pumps that have been in use for more than five years, the thickness of the oxide layer on the surface of the motor commutator reaches 8μm (new products <1μm), and the contact resistance value increases by three times. At -10℃, this resistance will further increase by 150%, forcing the working voltage to drop below the critical point of 9V. The technical report on the recall of 130,000 Cadillac vehicles by General Motors in 2020 confirmed that under such conditions, the fuel flow rate drops to 57% of the design value, and the air-fuel ratio during cold start is reduced to 18.5:1 (22% beyond the ECU control range). Specifically, the crankshaft needs to be turned more than five times before starting, and the increased load on the battery shortens its lifespan by 40%.
The clogging of the fuel pump filter screen has an amplification effect on low-temperature start-up. When the pore blockage rate reaches 30%, the flow resistance at -15℃ is 19 times higher than that at normal temperature. Volvo’s 2019 maintenance database statistics show that in vehicles with a mileage of over 100,000 kilometers, the peak pressure difference of the filter screen during cold start can reach 120kPa (the rated limit is 45kPa), and the flow rate drops sharply to 46L/h (less than 53% of the peak demand). At this point, the Engine Control module (ECM) will actively cut off the fuel injector pulse to prevent mechanical damage, causing the average number of attempts at sub-zero start to increase from 1.8 to 4.3 times. The power consumed by each failure is equivalent to working with all headlights on for 2 minutes.
The aging of temperature-sensitive materials intensifies seasonal problems. After 100 freeze-thaw cycles (alternating between -30℃ and 25℃), the hardness of the nitrile rubber sealing ring increased by 38 Shore degrees, resulting in a leakage rate of 0.7mL/min in the oil pipeline. Vehicle monitoring data from the Siberian region shows that when the ambient temperature is below -25℃, the incidence of fuel pump air blockage caused by seal failure is as high as 31%. At this point, the fuel vapor bubble occupies more than 15% of the oil passage volume, and the pressure fluctuation range reaches ±35kPa. It requires three consecutive starts to establish a sustained oil pressure. Each start causes the battery voltage to drop by 0.8V (167% exceeding the allowable maximum value of 0.3V).
The fuel Vapor Lock is the core obstacle for starting at extremely low temperatures. When the oil temperature is below the freezing point, the particle size of water crystals in ethanol gasoline is greater than 200μm. These crystals can accumulate at the fuel pump impeller and block 30% of the cross-sectional area of the flow channel. In the cold region tests conducted by TUV Germany in 2022, it was found that when vehicles using E10 gasoline were cold-started at -20℃, the slope of the pump body flow attenuation curve was 2.1 times steeper than that of regular gasoline. The SAE research report of the United States (2023-01-0072) confirmed that under extreme conditions, when the thickness of ice crystal accumulation at the blade edge exceeds 0.5mm, the axial clearance will decrease by 89%, causing the torque demand to surge to 280% of the normal value, and the probability of triggering overload protection power-off will increase by 11 times.
Preventive maintenance needs to focus on key thresholds:
Cold start oil pressure establishment time > 2.5 seconds (real-time monitoring by OBDII tool)
When starting for the first time in winter, the current fluctuation range is greater than ±25%
Fuel consumption in sub-zero temperatures increases by more than 15% compared to normal temperatures
The fuel pump with an optimized design for low-temperature characteristics (such as the integrated preheating circuit model) can increase the success rate of cold start at -30℃ to 98.7%, which is 37% higher than the standard design. This is equivalent to saving the vehicle an average of 6.5 rescue calls per month (each costing $220) and extending the starter’s lifespan by approximately 16,000 kilometers. Especially for diesel models, choosing a fuel pump with a PTC heating element can reduce the risk of clogging caused by wax precipitation in high pour point diesel by up to 91%.