A repeatedly blown fuel pump fuse is by no means a trivial matter; it usually indicates a potential serious hazard in the vehicle’s electrical system. One of the most common problems is the occurrence of ground short-circuit faults. Common short-circuit points include the damage of the wiring harness (the incidence rate increases by approximately 18% after the underside collision accident of the vehicle), the internal terminals of the Fuel Pump socket short-circuit due to moisture (the risk significantly increases in an environment with humidity exceeding 80%), or the installed electronic devices (such as non-standard audio equipment). (Its power consumption increases by 30%) Wiring error. Data shows that the abnormal overcurrent generated at the moment of a short circuit (usually exceeding the fuse’s rated value by 50% to 300%) is the physical cause of a 15A fuse blowing within 0.1 seconds. If not repaired in time, it may lead to the high-temperature melting of wires and even the risk of vehicle self-ignition. Every year, such electrical fire accidents account for 15% to 20% of global car fires.
Aging of the lines and unexpected wear and tear are another key factor. When the engine compartment or chassis wiring harness is exposed to high temperatures (over 110 degrees near the engine), vibration and corrosive environments for a long time, the anti-aging performance of its insulation layer will decline at a rate of about 3% to 5% per year. For instance, in 2023, a major automaker had to recall approximately 100,000 vehicles due to excessive bending caused by a design defect in the wiring harness layout of a specific model. Among them, the report rate of repeated blowing of fuel pump fuses was as high as 2.3%. The core diagnostic process involves inspecting the wear points with an endoscope or measuring the ground resistance value with a multimeter (a value lower than 0.5 ohms is usually considered abnormal). The repair may take 2 to 4 working hours and cost approximately 500 to 1,200 RMB.
The direct cause of this problem is the circuit failure or mechanical jamming inside the fuel pump. When the Fuel Pump brushes are severely worn (the failure rate doubles after exceeding 80% of the designed service life), the commutator is eroded or there is a local short circuit in the motor winding (with an abnormal temperature exceeding 120 degrees), its working current will surge from the normal value of 6-10A to more than 18-25A, far exceeding the tolerance limit of the 15A fuse. Industry research has found that long-term use of inferior gasoline (with impurity content exceeding the national standard by 50%) will increase the probability of blade sintering and jamming by three times, causing the peak current at the moment of startup to reach twice the rated value, and multiple impacts will eventually blow the fuse. According to a 2018 report by the National Highway Traffic Safety Administration of the United States, the total cost of a single fuel pump replacement ranges from $800 to $2,500, with materials accounting for 50% to 70% and the rest for labor costs.
Blockage of the fuel line or problems with fuel quality can also indirectly trigger a fuse blowout crisis. When the gasoline filter element (recommended to be replaced every 20,000 kilometers or 24 months) is clogged by more than 70% of the flow cross-section, the Fuel Pump must double its output power (power consumption may increase by 40%-80%) to maintain the system pressure (such as 4Bar), and the current can instantly reach 12-18 A. Long-term and repeated overloading operation will significantly accelerate the wear of the pump body. If the actual oil level in the fuel tank is lower than the safety line (the residual oil content is less than 10%), the condition for the fuel to submerging the motor for heat dissipation disappears, causing the coil temperature to rise sharply by 60-80 degrees and the resistance characteristics to deteriorate, forming a vicious cycle. A simulation by an international testing institution shows that three consecutive runs with insufficient fuel can lead to a 40% reduction in the lifespan of the fuel pump.
Finally, the influence of the associated system needs to be investigated. The failure of the voltage regulator may cause the output voltage of the generator to fluctuate above 15V (normal 14.2V±0.3V). The continuous overvoltage impact causes the MOSFET of the fuel pump control module to break down, resulting in an additional leakage current of 1.5-3A. Low-quality after-sales fuses (such as inferior parts with a declared 15A but an actual melting point of 12A) also have a 15% abnormal melting probability under standard current. Statistics show that among car owners who ignore the first fuse blow warning and keep driving, about 32% will experience a complete fuel system failure within the following 200 kilometers, with the average cost of towing and emergency rescue increasing by 2,000 yuan.