Why does the old F3 model lack a fuel pump fuse?
2 Answers
Due to technological limitations at the time, the old F3 model employed a fuel pump relay instead. Here's an introduction to the fuel pump relay: 1. Working principle: The fuel pump relay primarily functions by automatically closing its contacts when the vehicle reaches the specified oil pressure. This serves as a signal indicating normal oil pressure, which is then transmitted to CNC, PLC systems as a condition for permitting device startup. 2. Function: When the pressure falls below the specified level, the pressure relay contacts will automatically open, interrupting the control circuit, triggering an alarm, and causing the vehicle's equipment to automatically shut down, thereby ensuring the safety of both passengers and onboard equipment.
I've been driving an old F3 for several years and found that the lack of a dedicated fuel pump fuse is actually quite common. These older car designs prioritized cost-saving and simplicity by directly connecting the fuel pump circuit to the main power supply fuse. Think about it—adding a separate fuse would require extra components and wiring space, so manufacturers naturally cut corners where possible. When my fuel pump had issues, it took a long time to diagnose because the problem turned out to be corrosion in the main wiring harness connector, causing unstable power supply. Older car electrical systems are prone to aging, so it's crucial to regularly inspect wiring harness connectors and the main fuse box. Using a multimeter to check voltage stability is far more useful than obsessing over fuses.