1990 Mustang - Fuel Pump problems


I am having problems with my fuel pump. It keeps going continously. The only way to make the noise stop is to unplug the battery or my battery dies. I need a new fuel pump right?


I would check the fuel pump relay.


No, you don’t need a pump at this point.
Ford used several different wiring methods depending on the engine configuration.

The problem is more than likely a sticking fuel pump relay or it’s possible there could be an internal problem with the ECM, or engine computer.

You might look at the diagnostic connector for pulling codes, which is located under the hood.
Note if you see a tan wire with a green stripe in that connector.
If you do, and with the key in the OFF position, probe that wire with a test light that is connected to the battery POS terminal.
The test light should NOT illuminate; if it does, then you have an internal ECM fault. If it does not illuminate, then the relay is more than likely sticking.

A possible cause of a sticking relay is an old, worn fuel pump. A worn pump draws more current, which translates to more heat, and over time can burn the relay points causing them to stick.