fuel pump Problems, 2001 ford taurus 3.0l v6 vulcan

Having a problem with the fuel pump engaging. Warm or cold same problem. When I turn the ignition on I can hear the fuel pump engage and the car runs fine on start. Other times I turn the ignition on and don't hear the pump engage, thus no start. But repeatedly turning the ignition on an off I get the fuel pump to engage and I have start, will run until I shut it down. been doing this for a couple of weeks now. Is this an ignition thing or fuel pump? No wiring diagram. Replaced all relays, battery good. Never did anything with the fuel system. Looking for anyone that has run into this problem before.

There's a good chance that the issue is the fuel pump, but you could test for voltage out of the inertia switch when the pump doesn't run. If you have voltage out of the inertia switch toward the fuel pump, chances are even better that the issue is the pump. There's pretty much just wire and a couple of connectors between the inertia switch and the pump. Unfortunately it's essentially impossible to check for voltage right at the pump without dropping the fuel tank to get to the pump, so testing at the inertia switch is about as close as you can get.

-Rod

Thanks Rod for the info. -1 degrees here in the boston area today so I figured it would be a great time to try and start the car. Turned the key, heard the fuel pump energize and it ran. Let it run for awhile and then shut it down. Turned the ignition off and on several times and the fuel pump kept energizing giving me a start situation. I will check the inertia switch when it warms up a little. On a 2001 is it in the trunk or somewhere else? Thanks again

On your 2001 Taurus the inertia switch is in the trunk on the right hand side, behind the trunk liner.

The wire that leaves the switch and powers the fuel pump is the Pink wire with Black tracer in connector position #2 (middle). If you don't have voltage then when the car fails to start, then you may as well confirm there's power to the input to the switch, the Pink/Black wire in connector position #1. Keep in mind this circuit would only be energized for the same amount of time the fuel pump normally runs when the key is first turned to the Run position - about 1 second, so you'll need to make your measurement quickly. Having a helper or a meter with a Max Hold feature will be helpful.

-Rod