Why does the fuel pump fuse blow in the Mustang?

The most common causes are:

1. Short circuit: a short circuit in the fuel pump wiring can cause the fuse to blow. This can be due to damaged, frayed, or exposed wires coming into contact with the vehicle’s body.
2. Damaged fuel pump: if the fuel pump is failing or nearing the end of its life, it may draw more current than usual, which can overload the fuse.
3. Clogged fuel filter: if the fuel filter is severely clogged, the pump may work harder than normal to supply fuel, resulting in excessive current draw and causing the fuse to blow.
4. Incorrect fuse usage: if the fuel pump fuse has been replaced with one that has a lower amperage rating than specified by Ford, it is more likely to blow under normal operating conditions.

If the fuel pump fuse is blown, it’s important to identify and fix the cause of the overload before replacing it, to prevent the new fuse from blowing as well.

Other causes of fuel pump failure in the Mustang

If the fuel pump fuse is not blown, other possible causes of failure include:

1. Defective fuel pump relay: the relay controls the power supply to the pump. If this component fails, the pump will not receive power and will not operate.
2. Activated impact sensor: some vehicles have an impact sensor, also called an inertia switch, that cuts off power to the fuel pump in the event of a crash. If this sensor is accidentally triggered, the pump will stop working.
3. Engine Control Unit (ECU) problems: the ECU controls many functions in the vehicle, including the operation of the fuel pump. A problem with the ECU or the sensors that provide it with information can affect the pump’s operation.
4. Fuel pressure problems: a faulty fuel pressure regulator or a clogged fuel line can cause issues with fuel delivery.
5. Other causes: as mentioned earlier in the case of the fuse, a defective fuel pump, wiring issues, or a clogged fuel filter can cause the fuel pump to stop working, even if the fuse is not blown.

To diagnose the problem, it’s helpful to check if power is reaching the pump during startup. If there is power but the pump doesn’t work, the pump is likely faulty. If there’s no power, the issue is likely electrical or with the ECU.