My daughters boyfriend was driving his 98 Expedition this evening and it died. From what he is telling me, he said it just all of a sudden lost power. As he was coasting to the side of the road, he said the RPMs where fluctuating then died. It cranks but won't start. No "theft" light flashing. All fuses under the hood are good. Turning the key, can not hear the fuel pump pressurizing. No pressure at the shrader valve on the fuel line. While trouble shooting, found where someone had done a hack job of splicing the ground battery cable, wire was just folded over to hold together.
As we were towing it home, they said there was a beeping coming from behind the glove box, which is where the PCM is I think.
Kinda stuck on wether it could be PCM or fuel pump.
Would greatly appreciate any guidance.

 

Does the check engine light light up when the key is first turned from OFF to RUN? If not, the PCM isn't powering up.

If the PCM powered up, gain access to the inertia switch. Connect a test light or meter to the fuel pump power circuit, and see if it goes HOT during the pump priming cycle, ~2 seconds long at power-on. You need to determine which half of the truck to focus on.

The PCM doesn't have a beeper. The only things that should have that capability would be the GEM and airbag diagnostic module. The airbag diagnostic module is behind the glovebox.

 

yes check the things in the previous post

I'd bet any wierd noises you're hearing are caused by low voltage from trying to start the engine. electronics don't like low voltage.

I don't think any Ford is known for just crapping out because the ECM just suddenly dies
I'd be more inclined to think fuel pump.
as they do go bad frequently.
I'd troubleshoot to that end.

 

Update:
When we turn the key on, check engine light does come on. Have not checked the inertia switch yet. He went ahead and bought a new fuel pump. When we dropped the tank, the filter on the fuel pump was coming apart, the mesh had separated. I'm "assuming" that some of the internal stuff from the filter made its was into the pump.
Battery was too dead to crank for more than about 5 seconds and my jump box was dead. Have it charging and will check it tomorrow. It's 1:50 am and I have to be up at 4:30 to go to work. Hopefully it starts in the morning. I will post an update as soon as I have one.
Thanks for the assistance.

 

Ok. After letting the battery charge for several hours, he tried to start it and it started right up. But the fuel gauge didn't work. He drove it around all day. Just got a phone call, broke down on the side of the road, exact same problem.
Never got around to checking the fuel pump relay, or the inertia switch.
Im thinking it could be the relay on its last leg. I can't imagine the inertia switch causing this intermittent problem.

 

I'd start leaning towards a failing fuel pump.