Low-temperature Fuel supply capacity of the Fuel Pump is the most important parameter for improvement in cold start performance. The fuel pump should be capable of generating an initial oil pressure of not less than 250 kPa within 3 seconds at -20° C according to the SAE J2719 standard. Otherwise, the fuel injector particle diameter of atomized particles will increase from 50 μm at room temperature to 120 μm, which will be an increase in the probability of air-fuel ratio (AFR) being distant from the theoretical value of 14.7:1 by 42%. For instance, Bosch’s 044 fuel pump, through the use of a ceramic heater element (rated at 8W and heating rate of 2°C/second), can provide an oil pressure fluctuation rate of less than ±5% at -30° C. It has been subjected to testing by the Norwegian Arctic truck fleet to reduce the cold start time from 8 seconds to 2.5 seconds with a success rate of 98%.
The cold start stability is affected by the low-temperature tolerance of fuel pump material. Polyetheretherketone (PEEK) material impellers in fuel pumps (density 1.3g/cm³) (such as Walbro F90000267) experience a torque loss 78% lower than that of conventional nylon impellers at -40°C, and the rate of flow attenuation drops from 30% to 8%. The 2022 extreme cold test in Quebec, Canada proved that when vehicles with this pump started at -25°C in the cold conditions, fuel flow rate dropped only from the nominal 65 L/h down to 60 L/h, but flow rate of the traditional pump dropped down to 45 L/h, and the starting failure rate decreased from 19% to 3%.
Low-temperature rate of response of the electric system of the fuel pump is a very important parameter. Fuel pumps fulfilling the requirement of ISO 16750-4 standard should have a winding resistance deviation of not more than ±10% at -40°C and such that the time to motor speed to increase from 0 to 3000 rpm should be no more than 0.8 seconds. For example, Delphi FE0114 fuel pump employs silver-carbon composite brushes (resistivity of 0.8×10^-4 Ω·m), and cold start current is 5.8A at -30°C (9.2A for copper brush mainstream pumps). The voltage fluctuation range drops from ±18% to ±6%. It has been tested and confirmed by the Siberian freight fleet that it decreases cold start circuit failures by 63%.
Synergy of the fuel additive and fuel pump can enhance the efficiency in cold start. According to ASTM D4814 standard, using the fuel pump to dispense gasoline containing ≤15% ethanol content, upon blending with high-strength cold start additives (e.g., Red Line SI-1, 12% ethylene glycol content), one can reduce the freezing point of fuel from -24°C to -37°C and reduce the inner flow resistance of the pump casing by 28%. The on-road trials conducted by end users in Alaska in 2021 demonstrated that after treatment of Continental VDO FP-7-1-003 fuel pump and additives, the -30°C cold start fuel pressure increased from 180 kPa to 260 kPa, fuel injection pulse width decreased from 12 ms to 8 ms, and the combustion efficiency was improved by 22%.
Fuel Pump maintenance cycle has a significant effect on cold start reliability. Tests show that when the fuel filter clogging degree is greater than 50% (pressure drop > 70 kPa), the attenuation rate of low-temperature flow of the fuel pump can be as high as 40%, and the cold start time will be extended by 300%. NHTSA’s 2023 recall statistics indicate that one American brand’s cold start failure rate at -15°C has increased by 34% because of a design flaw in the fuel pump filter (80 PPI pore density, below the industry standard pore density 120 PPI), and the cost of recall per unit amounted to $890. For cars changing the filter every 20,000 kilometers, the fuel pump’s lifespan can be extended to 150,000 kilometers (from 100,000 kilometers), and cold-start upkeep costs can be reduced by 65%.
Confirmed verification by experts indicates that low-temperature efficiency of the fuel pump can be systematically improved through optimization. According to TUV SUD’s “Certification Specification for Vehicle Components in Extreme Cold Environments”, select the fuel pump tested for durability test at -40°C/500 hours (fluctuation in oil pressure < ±3%) and is for high-flow injector compatibility (>200 cc/min). The CO emissions released during cold start can be reduced from 1.2 g/km to 0.5 g/km (the regulation value of Euro 6 norm is 1.0 g/km). For instance, Tesla’s Cybertruck integrated fuel pump system with a PTC heater reduces battery load by 18% and increases motor torque output speed by 0.4 seconds for -20° C cold start. Consumer Reports listed it as a “benchmark for extreme cold technology.”.