The detection of short circuits in the Fuel Pump circuit requires the combination of electrical parameter analysis and physical phenomenon observation. Under normal working conditions, the circuit resistance of the fuel pump should be between 0.5 and 3 Ω (in accordance with the SAE J1128 standard). If the measured resistance is lower than 0.2 Ω or approaches zero, a short circuit may occur. When conducting continuous tests with the Fluke 87V multimeter, short-circuit points are usually accompanied by local temperature rises – when the wire harness temperature exceeds 80°C (at an ambient temperature of 25°C), it is considered abnormal. Infrared thermal imagers (such as FLIR E6) can precisely locate areas with a temperature difference of ≥ 15°C. For instance, in the 2022 NHTSA recall case, for a certain model, the insulation layer was damaged due to the friction between the fuel pump wiring harness and the frame, resulting in a short-circuit current of 25A (rated value 10A), which led to an eightfold increase in the fuse burnout rate.
Voltage drop testing is another key means. When the Fuel Pump is in operation, the voltage drop between the power cord and the grounding wire should be ≤ 0.5V (for a 12V system). If the measured voltage drop is ≥ 1.2V, it may indicate an abnormal line resistance. According to the 2023 study of “Automotive Electrical Systems”, the voltage fluctuation caused by a short circuit can cause the rotational speed deviation of the fuel pump motor to reach ±15% and the flow error to exceed 10%. The probability of triggering the ECU fault code P0230 (fuel pump primary circuit fault) increases by 62%. In actual operation, the PicoScope 4425 oscilloscope is used to capture the current waveform. During a short circuit, the peak current can suddenly increase to 30A (the peak value of the normal waveform is approximately 12A), and the waveform presents high-frequency oscillation (frequency > 1 kHz).
In terms of physical inspection, short circuits are often accompanied by carbonization of the insulation layer of the wire harness (the resistivity of the carbonized area is ≤ 10^3 Ω·cm) or terminal melting damage. A certain maintenance case shows that the Fuel Pump circuit of the Ford F-150 suffered from oxidation and corrosion of the copper wire due to water ingress (humidity > 90%), and the insulation resistance dropped from 50 MΩ to 0.5 MΩ, causing intermittent short circuits. The fault was manifested as random engine stalling (with a frequency of 2-5 times per hour). At this time, a megohmmeter (such as Megger MIT410) should be used to measure the insulation resistance of the cable. If the value is lower than 1 MΩ (ISO 6722 standard requires ≥ 10 MΩ), deterioration can be confirmed.
In data-driven diagnosis, the abnormal duty cycle signal of the fuel pump of OBD-II is an important indicator. The normal duty cycle range is 25-85%. If the ECU continuously outputs a duty cycle of more than 95% but the fuel pressure is still lower than the nominal value of 45 psi (error ≥ 20%), it may indicate a short circuit in the line causing power loss. A patent of Tesla in 2021 (US20210122345A1) shows that by monitoring in real time the deviation of the current integration value of the Fuel Pump (normal range 8-12 A·s) from the preset threshold, it can warn of the short-circuit risk with a 98% probability in advance.
Industry norms require that the short-circuit detection of wire harnesses needs to carry out the pulse immunity test of ISO 11451-4 to verify that the signal bit error rate is ≤ 0.1% under an electromagnetic field strength of 100 V/m. For modified vehicles, the use of shielded twisted-pair cables (with a shielding effectiveness of ≥ 40 dB) can reduce the risk of short circuits – actual measurements show that this measure can lower the misjudgment rate caused by high-frequency interference from 12% to 0.5%. Emergency response suggestions: Once overheating of the line (> 90°C) is detected, immediately cut off the power and use high-temperature resistant sleeves (such as Teflon PTFE, with a temperature resistance of 260°C) to isolate the damaged points to avoid secondary disasters caused by the ignition of fuel vapor (ignition point 250-300°C).