An electric fuel pump does not run, when a jump wire is connected to energize the fuel pump relay coil, the pump runs. What does this indicate?

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Multiple Choice

An electric fuel pump does not run, when a jump wire is connected to energize the fuel pump relay coil, the pump runs. What does this indicate?

Relaying function matters: the fuel pump is powered when the relay coil is energized, which closes the contacts and lets battery voltage reach the pump. If applying a jump wire to energize the relay coil makes the pump run, the coil, the relay contacts, and the pump wiring are capable, so the problem isn’t with the pump or the relay itself. The issue is that under normal operation the coil isn’t receiving power from the control circuit (ignition switch/fuse/wiring) to energize. In other words, there’s no power reaching the coil in the normal circuit. That’s why the correct interpretation is that there’s no power to the coil. A bad ground isn’t the primary cause here because energizing the coil directly with a jumper works, which means the ground path is fine. The pump isn’t defective, and the relay isn’t faulty.

Relaying function matters: the fuel pump is powered when the relay coil is energized, which closes the contacts and lets battery voltage reach the pump. If applying a jump wire to energize the relay coil makes the pump run, the coil, the relay contacts, and the pump wiring are capable, so the problem isn’t with the pump or the relay itself. The issue is that under normal operation the coil isn’t receiving power from the control circuit (ignition switch/fuse/wiring) to energize. In other words, there’s no power reaching the coil in the normal circuit.

That’s why the correct interpretation is that there’s no power to the coil. A bad ground isn’t the primary cause here because energizing the coil directly with a jumper works, which means the ground path is fine. The pump isn’t defective, and the relay isn’t faulty.

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