The typical operating current range of electric fuel pumps for gasoline engine vehicles (such as the Bosch 044 series) is 4A to 12A, and the peak current at the moment of startup can reach 250% of the rated value. According to the SAE J554 standard, the rated current of the fuse should reach at least 135% of the steady-state current. A 2019 research report by the Society of Automotive Engineers of North America shows that 92% of passenger car fuel pumps use 10A to 15A fuses, but the actual specifications need to match the power of the pump body. For example, a 120W high-flow pump (with a working voltage of 13.5V and a current of 8.9A) needs to be equipped with a 12A slow-fuse, and its fuse melting time needs to be delayed by more than 0.5 seconds when overloaded by 200%.
Improper selection of fuses can lead to double risks. A fuse value that is too low will generate a 22.3% false fuse probability (J.D.Power 2022 Vehicle Electrical Fault Report), while a fuse value that is too high will increase the risk of wire overheating by four times. Ford’s 2021 recall incident revealed that due to the incorrect installation of a 20A fuse to protect the fuel pump module that only requires an 8A, the temperature of the wiring harness could rise to 180°C during a short circuit, exceeding the limit temperature of the wire insulation layer by 60%, ultimately causing seven vehicle self-ignition accidents.
High-temperature environment has a significant influence on the melting characteristics. Laboratory data shows that when the engine compartment temperature rises from 25°C to 85°C, the melting threshold of the 15A fuse of the same model will decrease by 18%. For this reason, Honda R&D has specially stipulated in the Southeast Asian market that the Civic Type-R model must adopt a ceramic body fuse with a temperature resistance of 125℃, and the deviation of its melting accuracy at high temperatures is controlled within ±5% (the deviation of the ordinary plastic shell is ±15%).
There are special considerations in the field of racing. The Electric Fuel Pump of the Porsche 911 GT3 Cup racing car operates at a current of 22A, but uses a 25A fuse. This is because its equipped current slow rise system can reduce the starting impact from the peak of 45A to 32A, and the fuse needs to withstand a continuous overload condition of 110% for 30 minutes. Comparative tests show that when using the standard 15A fuse, the probability of the fuel pump module of this racing car melting within a single lap at the Nurburgring Circuit is as high as 36%.
Cost-benefit analysis indicates the economy of optimal configuration. The cost difference between replacing the original 15A fuse (unit price 2.5) and dealing with the fuse fault (average repair cost 180) is as much as 72 times. Internal data from the Volkswagen Group shows that correctly matching fuse specifications can extend the lifespan of oil pump motors to 150,000 kilometers (a 40% increase compared to non-matching schemes), and extend the wiring harness replacement cycle from 6 years to 10 years.
Extreme cases confirm the necessity of safety margins. At the 2023 Dakar Rally, the Toyota Hilux racing car, which was modified with a high-flow oil pump and equipped with a 25A fuse, maintained system integrity even when experiencing voltage fluctuations (transient voltage 18.6V) on desert sections. However, the competitor withdrew from the competition due to the use of a substitute that did not match the actual fuse curve of the claimed 15A and suffered an oil circuit failure under the same working conditions.
