Forum > 4.6 Mustang technical forum

Fuel Pump Won't Shut Off


I'm a newbie with Mustangs & am trying to help my son with a 1998 Cobra he just purchased. Was running fine until yesterday when one of the fuel pumps (I'm told there are two) won't shut off, even with the ignition turned off and key out. Only way to shut off fuel pump is by disconnecting battery pole. Any tips, advice or help as to how or where to diagnose &/or fix the problem would be greatly appreciated. Appreciate the help.

Try this.  In your trunk you have a fuel pump shut off switch located on the driver's side next to the tail lights.  Hit the red button to shut it off, then try to start and run.  If it won't go, then hit the red button again, which will essentially reset the pump to go.  If this doesn't work, then the switch is FUBAR. 

Thank you. I found what was called a "First Inertia Switch" with a red button on the top by the driver's side tail lights in the trunk. It was depressed & it  wouldn't do anything when you pressed it. So I unhooked it and played with it. Is it supposed to bounce back up after you press it? The only way it pops back up is if I push it up with a tiny screwdriver. I tried it both ways, with the red button up and with it down, and the fuel pump continous to run either way. Is it the switch then for sure? When you press the switch is it supposed to shut the fuel pump? Sorry for my ignorant question but if I replace the switch will that fix the problem and shut off the fuel pump? Thank you.

Yes, that is your problem.  The switch is FUBAR. 

For some unknown reason, my fuel pump keeps running while the battery is in the ignition that hocked up. Because if the fuel pump is running and delivering normal pressure to the engine, it will take good for your engine. However, we should know that there is some case that the fuel pump relay to take over the  run of the fuel pump. Basement Dehumidifier SEO Services


[0] Message Index

Go to full version