When pre-charging the new Fuel Pump, the fuel system needs to establish an initial pressure of at least 3.0bar to ensure normal startup. According to the SAE J2716 standard, using a manual vacuum pump (such as Mityvac MV8500) to vacuum the fuel pipeline to -0.8bar and maintain it for 30 seconds can eliminate 90% of the residual bubbles. The TUV test in 2023 showed that this method reduced the cold start time of diesel engines from 12 seconds to 3.5 seconds and compressed the fuel flow error from ±8% to ±1.2%. Taking the Volkswagen EA288 engine as an example, the oil pressure establishment time recorded by the ECU after correct precharging is 1.8 seconds (6.2 seconds without precharging), and the fluctuation range of the air-fuel ratio λ value is optimized from ±0.4 to ±0.08.
The exhaust process of the fuel system needs to precisely control the flow rate and time. Data from the Bosch FSA 740 diagnostic instrument shows that by activating the Fuel Pump pre-charging mode through the cyclic ignition switch (operating ON/OFF 5 times with an interval of 2 seconds), the pipeline filling can be completed within 45 seconds, with a fuel consumption of approximately 120ml (traditional manual exhaust consumes 300ml). The Volvo VNL truck maintenance manual states that this method increases the exhaust efficiency of the diesel filter by 67% and keeps the temperature rise of the oil pump motor within 15°C (the safety threshold of 35°C).
In a low-temperature environment (-20°C), additional heating measures are required for pre-charging. The Delphi HP10132 Fuel Pump is equipped with a built-in PTC heating module, which can raise the fuel temperature from -30°C to -5°C within 120 seconds (reducing the viscosity from 850cSt to 300cSt). Combined with the intelligent temperature control algorithm, the establishment time of fuel pressure is shortened by 58%. The actual test of the Alaska freight fleet shows that this technology has reduced the winter cold start failure rate from 23% to 0.7% and lowered the risk of ice crystal blockage in the fuel pipeline by 92%.
Calibration of pressure sensors is crucial to the quality of precharging. When adjusting the Fuel Pump pressure sensor using the Fluke 754 process calibrator, it is necessary to ensure that the output signal error is ≤±0.02V (corresponding to a pressure error of ±0.15bar). In 2022, Volkswagen Group recalled 110,000 diesel vehicles due to sensor calibration errors. The pressure deviation recorded by the ECU of the faulty vehicles reached ±0.5bar, resulting in a 12% deviation in fuel injection. After correct calibration, the fuel economy improved by 4.7% (the fuel consumption per 100 kilometers decreased from 5.2L to 4.95L).
The cost-benefit analysis shows that although the unit price of professional pre-charging tools (such as Schley 66000) is 220, the failure rate can be reduced from 6.5480 (including parts and working hours). Statistics from NHTSA show that the average lifespan of Fuel pumps that are not pre-charged correctly is shortened by 37% (from 150,000 kilometers to 94,000 kilometers), and the probability of damage to the fuel injection system increases by 14 times. Adopting the ISO 16750-2 standard operating procedure, the payback period of investment is only 8 months (calculated based on an average annual driving distance of 30,000 kilometers).