Hi Guys,
I just bought a 2003 XLT, 5.4, 93K, a clean, well maintained truck. I was on the highway yesterday and the truck died, coasted to the side of the road and called a tow. It did set the eng light and a P0320 code. As I was waiting for the tow it would start and run but after 30 sec of idling it would die, like it ran out of fuel or if I started it back up and reved the enging as soon as it came back down it would die but start right back up.
After some research I am lead to a Crank pos sensor, no problem, I replaced it in my 99 so no big issue, but I also read to look for the harness that comes from the alt to the battery as it rests on the AC tube and can wear through and short, I looked at the wire, pulled the tape back and there is no wear at all.
So I started the truck and the battery light is still on so I took a jumper wire and went from the alt to the battery, basically in my mind replicating the fusible link but the battery light didn't shut off, maybe that wasn't the right way to test it but in my mind I tried it.
It almost seems as if, coincidently, I got 2 problems at the same time? the P0320 (crank pos sensor) and the battery light or are they connected?
I am also confused as it seems it would run out of fuel? is that because once the ckp isn't sending a signal it shuts the fuel off??

Any direction to head or just replace the fusable link harness between the alt and battery as well as the CKP sensor?? I was also made informed of teh fuel pump relay inside the fuse panel may burn out or fail under load.
Is it coincedence that all this happened at once or is the faulty crank sensor not sending a strong signal so the fuel pump is dying??

I know this is simple maintenance stuff but other than this I love the truck

Thanks

 

You might want to get a VOM and fuel pressure tester.
If you have proper fuel pressure then you know the fuel pump relay is fine.
If you don't have proper fuel pressure then you can test the relay circuit with the VOM.
Also, you can test the alternator/battery circuit with the VOM.
With the engine running the system should read around 13.4v.
My guess is the alternator is not working and the system voltage is 12.4v which would mean the engine is running off the battery.
I doubt the fusible link is bad.
The alternator has a second 12v wire with a 10A fuse #9.
Harbor Freight's VOM (free with coupon) and fuel pressure tester ($15) are adequate.

 

OK, but why does it seem I have 3 situations, the Fuel issue, P0320 as well as the battery light??

In an effort to diagnose the battery light I tested the battery 12.6v. I then started the truck and tested voltage at the battery and while running its 11.4v with loads on. I wiggled the fusible link around to see if it had an effect on the reading and it did not.
I guess my question is is it possible I have 3 issues making happen all at once, (battery light, the P0320 code crank pos sensor, and the fuse box, fuel pump relay) I went on a 420mile trip with zero issues 2 days before

 

What should my fuel pressure be at the fuel rail schrader valve?

 

My guess would be that it's possible the alternator is causing all of the problems. 11.4 while it's running is certainly too low.

 

I agree and I am going to address that first as (I am sure nothing operates correctly without correct voltage

 

Did you check fuse #9?

 

I have not yet, I have been juggling work, class etc
Where is teh #9 located?
I did check the 20amp in the pass kick panel #34 I think

 

Here's my SWAG:
Alternator dropped out.
Vehicle voltage dropped too low.
PCM lost the bias voltage to the CKP.
PCM thought the engine stopped turning.
Therefore the PCM shut the fuel pump off.


I'd start by charging the battery to full charge.
Then see if it will run.
If it does, solve the alt issue.
(The P0320 and fuel issue may disappear. )


Probably should move this to the Truck Forum.

 

Um, why, it's a 2003 expedition XLT?

 

Thanks, I thought I was missing something

 

Oh. Okay.
I thought it said 2003 XLT Truck.
My bad.

 

No worries, Thanks for your advice. I was kinda leaning in that direction but needed to hear anothers thoughts. I will report back once I install a new alternator

 

Sub'd. I just went thru this with it cutting off. These expeditions were bad about the fuel pump relay going out. It would run fine until the relay got hot and broke contact from the interior fuse box board. There is a guy in VA. that repairs the fuse boards as the fuel pump relay is non-servicable. Let me know if your alt replacement doesn't fix the problem.

 

I will and the fuse panel is where I was leaning but first, its possible that the bad alt sent everything haywire and second, I cant do any testing until the charging system is working correctly.