2001 Taurus fuel pressurization

Our Taurus has been having problems with starting, but the problem seems totally intermmitent so it is difficult to pin down. We think it is a fuel pressure problem since we can't hear the system charge when we turn the ignition key. Every time we do hear it charge, the car starts. It only happens when the car has been driven a little while, sits for a short period of time and then we go to start it up again.

There have never been any perceptible problems during normal driving conditions if the car did start (which is causing us to think it isn't the fuel pump). Swapped out the fuel pump relay, but car still didn't start. After the car sits for 5-7 hours, it always starts again.

What can cause the fuel system to not pressurize, but only has an affect when you are trying to start the car?

Your symptoms sound pretty consistent with a weak fuel pump. The fuel pump is a DC motor with brushes that wear. Similar to a starter motor, when hot a weak/faulty motor can fail to get continuity with the commutator or through the windings. As it cools, the open circuit contracts and again makes contact, thus allowing the motor to spin again.

You could just replace the pump, but if you want to have high confidence the pump is your problem, you can attach a multimeter to the fuel pump and trigger the "Max" feature. Attach a fuel pressure guage to the fuel rail Schreader valve, then turn the key to crank the engine. If you see a Max reading of nearly battery voltage at the pump and see virtually no fuel pressure, chances are pretty good the pump is bad. This is assuming you don't have a restricted fuel filter or fuel line.

-Rod