'03 Ford Expedition dying while driving, will restart eventually

My wife has an '03 Ford Expedition with 110k miles on it. It began dying while driving. Sometimes while moving. Other times when stopping or idling. She would describe that sometimes when it began acting like it was going to die she could “give it gas” and it would revive, other times that wouldn’t work. It would usually restart after one or two tries. Our local mechanic did a tune up and replaced a coil. During the trip she began hearing a sound of “metal shredding” and the car died and wouldn’t restart. She had it towed to a ford dealer. They replaced the IAC valve. After that the dying would continue but instead of dying right away it would “lose acceleration, and eventually die within a few seconds” Took it to another ford dealership and they replaced the fuel pump and relay. It would work fine for a few weeks and then start dying again. Another local mechanic noted the error code P0231 “Fuel Pump Secondary Circuit Low” He kept it for a few weeks and was able to get it to die for him once but not again. The dying continued. Sometimes it would work great for weeks, other times it would die continually on the same trip. Took it to a 3rd dealer and they couldn’t find anything wrong.
It dies in the cold and in the heat. Usually after driving at least 20 minutes into a trip. Once it dies once it will typically continue to do so until resting for a day or so. Sometimes with a full tank of gas, sometimes with a low tank.
Any ideas?

Given the P0231 code, it seems apparent that wiring for the whole fuel pump circuit needs to be checked. Has anyone done this? If the check engine light still on and the code still present?

I think by “secondary circuit” it is referring to the after-relay part of the circuit. That is the circuit which goes directly to the fuel pump. The primary part of the circuit would be the part that enables the relay presumably.

If I had this problem I’d hook up a DVM right at the fuel pump and monitor the voltage while I drove the vehicle. If the voltage drops at the same time the problem occurs, then at least you know what the cause is – the fuel pump isn’t getting its needed power. The cause at that point should not be too difficult to find for a competent auto-electric tech.

My guess is that a connector is the wiring harness going to the fuel pump is burned or corroded. This can be caused by a fuel pump on the fritz, as that will cause more current to flow in the circuit. Since you’ve replaced the fuel pump, that wouldn’t be the cause now, but the connector could have been damaged from the prior fuel pump and still be not making a good electrical contact.

A fuel pressure measurement may be in order also.

Inspect inertia switch terminals for burning. Replace as needed.

There is a well-know issue about a bunt connection in the central junction box in the right front kick panel.

This is a smart junction box so it has built-in relays and the entire box may have to be replaced.

Have dealer investigate central junction box and inertia switch.