What relay is the fuelpump?
3 Answers
fuelpump is not a relay, it is a fuel pump. The following is an introduction to the function of the fuel pump and precautions for use: Function of the fuel pump: The fuel pump is one of the basic components of the fuel injection system in an electronically controlled fuel injection vehicle, located inside the fuel tank. Its function is to draw fuel from the fuel tank, pressurize it, and then deliver it to the fuel supply line, working in conjunction with the fuel pressure regulator to establish a certain fuel pressure. Precautions for use: The fuel pump operates when starting and while the engine is running. If the engine stops but the ignition switch remains in the 'on' position, the HFMSFI control module shuts off the power to the fuel pump to prevent accidental ignition.
The fuel pump relay is essentially a current transfer station specifically designed to control the fuel pump's power supply. Think about it - if the fuel pump were directly connected to the battery, the excessive current could easily burn out the wiring. That's why automakers designed this little box to act as an intermediary. It takes commands from the ECU computer: when you turn the key to the ON position (before starting), it activates the fuel pump for two seconds to build up oil pressure; during engine cranking, it provides continuous power for fuel delivery. In my old Toyota, the fuel pump relay is located in the fuse box under the steering wheel - that blue rectangular block with five pins. Last time when the car wouldn't start, the mechanic spent ten minutes testing with a multimeter before confirming it was relay contact burnout. When replacing it, you must find an exactly matching part number - incorrect installation might cause intermittent fuel pump failure. This component usually goes unnoticed, but its failure can instantly leave your engine completely paralyzed.
My car repair experience tells me that fuel pump relay failure is a common culprit for vehicle no-start conditions. This relay is essentially an electromagnetic switch that converts low-current signals into high-current power to drive the fuel pump. When the ignition key is turned, the engine control unit sends a signal to the relay, causing its internal contacts to close and supply power to the fuel pump. The most frustrating part is that its working status can't be visually inspected. Last time when my neighbor's car suddenly stalled, I used a makeshift method by swapping the AC relay to the fuel pump position for testing, and the car immediately returned to normal operation - this confirmed the diagnosis. Most vehicles hide this small cube in the engine bay fuse box or behind the instrument panel side cover, requiring professional tools to remove interior panels for replacement. If you notice the fuel pump makes no sound during startup, don't rush to replace the pump - there's an 80% chance this relay failed first.
