When disassembling the old fuel pump in the plastic fuel tank, it is necessary to strictly follow the safety procedures. First, ensure that the vehicle has been turned off for at least 30 minutes to allow the fuel tank temperature to drop below 40℃, and avoid the gasoline vapor concentration exceeding the lower explosive limit (1.4%). For instance, in the Ford F-150 recall incident in 2019, the probability of maintenance fires caused by the failure to cool the fuel tank increased by 15%. Before operation, the pressure of the fuel system needs to be released. By removing the fuse of the fuel pump (usually located at position 15A of the fuse box on the driver’s side) and starting the engine until it is turned off, the residual pressure can be reduced to below 0.5 bar. Wearing anti-static gloves (with a resistance value of less than 10⁹Ω) and using explosion-proof tools can reduce the risk of static sparks (ignition can occur when the discharge voltage is greater than 1000 volts).
Before disassembling the fuel tank, the fuel needs to be drained. Use a siphon pump to extract the remaining fuel at a flow rate of 4 liters per minute (the residual amount should be less than 5% of the fuel tank capacity). Take a 60-liter fuel tank as an example, the residual capacity should be controlled within 3 liters. Lift the vehicle to a height of 50 centimeters from the ground. Remove the bolts of the fuel tank fixing belt (usually 4 M10 bolts, with a torque value of 25 N · m). Use an 8mm socket in combination with a torque wrench, and the deviation should be controlled within ±2 N · m. According to the SAE J2530 standard, the weight of the plastic fuel tank is approximately 8-12 kilograms, and two people need to collaborate to prevent deformation (the maximum load-bearing pressure is <50 Newtons).
Opening the fuel tank maintenance port is the core step. The fuel pump assembly is usually fixed by a lock ring (with a diameter of 20 cm and a thickness of 3mm). A special lock ring wrench should be used to rotate it counterclockwise by 30 degrees to remove the buckle. According to Toyota’s maintenance data in 2022, the rate of lock ring breakage caused by violent disassembly was as high as 18%, and the replacement cost increased by $200. To remove the residual sealant, a non-metallic scraper should be used to avoid scratching the oil tank (surface roughness Ra<0.8μm). When unplugging the fuel pump, maintain a 45-degree Angle to prevent the floating arm from deforming (bending limit <5 degrees), and at the same time disconnect the circuit interface (the force for plugging and unplugging the terminals is approximately 50 Newtons).
The fuel tank needs to be cleaned immediately after the old fuel pump is removed. When wiping the inner wall with non-woven fabric, the residual particulate matter should be less than 0.1 milligrams per square centimeter. When inspecting the cracks in the fuel tank, the pneumatic test method is adopted (pressurize to 0.3 bar and hold the pressure for 2 minutes, with a pressure drop of <0.01 bar). According to EPA regulations, waste fuel pumps must be handed over to certification bodies for processing (with a recovery rate of 85%). For instance, in 2023, the California Environmental Protection Agency fined each case of illegal dumping $500. Before installing a new fuel pump, it is essential to replace the sealing ring (with a compression permanent deformation rate of less than 20%) and apply fuel grease (with a temperature resistance range of -40℃ to 120℃) to ensure that the probability of seal failure is less than 0.1%.