I have a 2003 f150 stx 4x4 with the 4.6 248,000miles 5speed manual. Was driving and the motor just shut off. Was able to load on a trailer by cranking the starter while in first gear. Was told it was the timing chain, but I think it might be the fuel pump. Any ideas?

 

when you turn on the key ( but don't crank start), you should hear the fuel pump run for 3 seconds to build up pressure.......... Under the hood, above the motor, there is a fuel line (rail) feeding each bank of 4 cylinders... somewhere on that line is a Schrader valve ( like an air valve to fill a tire). if you take off the plastic cap and use a BIC pen to push the center pin in the valve, it should shoot out a few drops of fuel.. it should have about 40 psi pressure on it.. turn the key on 2-3 times to buildup pressure from the fuel pump, then push the Schrader valve again and test for PSI.

 

Got it towed to the house and cranked it over. It started for a second and shut off again. I noticed the theft light was flashing. Checked the fuel pump and it is running.

 

Turn the ignition switch to RUN only and let is set for a couple minutes.
If the Theft lamp flashes a two digit code post it here.
Good luck.

 

The anti-theft system cannot cause an engine that is already running to shut off. It can, however, keep it from restarting if triggered. Red herring...

 

New info...truck will start but makes a lot of noise, I can keep it running feathering the gas but it will shut off as soon as I let off it.

 

Ouch...
probably not your case but...
I had a air filter disintegrate, ( no, it was not that old, the glue let go and the reason I do not recommend Fram products). A piece of the filter media happen to land on the MAF sensor. Shut it off like a switch and wouldn't restart like you described, restart & run like for 1-2 seconds & die again. I wasn't long on the turning it over either. Cleaned the MAF sensor and dropped in a new air filter and I was good. The difference from my situation to yours is that I did not have strange noises after restarting and I did not have to feather the throttle.

Couldn't hurt to check out that airfilter

 

Definitely not the air filter, It's got a K&N filter in it.

 

I'd have to say you are wrong, good sir. I was driving home one day when the truck shut off. Theft light was rapidly flashing, and the truck refused to start back up. Towed it back to the lot, and did a little research. Next day, replaced PCM relay. Started right up.

PATS CAN shut the truck off while it's running. First hand experience here.

 

My information IS correct, it comes directly from Ford. The software that implements that PATS function is only active when starting the vehicle, it is COMPLETELY out of the picture after that. See https://www.motorcraftservice.com/vd...b_aid_2013.pdf

What you saw is likely the result of a momentary loss of power feed to the PCM which caused a momentary stall of the engine and an invalid PATS read when the power came back on. Guess what causes that problem most of the time? Yep, the PCM Power Relay which you replaced and which repaired the problem. Point made. PATS did NOT cause your stall.

You have to understand HOW the system works....


.

 

Project is correct.
The PATS is no longer in any control once the motor is running.
If power is lost to the PCM, the motor stops.
It amount to a reset bringing the PAT 'back active' as it is needed to supply the PCM with validation AGAIN, for a restart.
This is how the anti theft has to work to be worthwhile.
Certainly the Theft WILL FLASH at a restart if the PCM has no power because the PATs, the Dash and the PCM all have to respond to the key code, and ignition on, to complete the [start bits in the ID word in the PCM program] for a new start.
Your just not awhere of all that goes on.
Good luck.

 

I have a decent understanding of the system. It's a multi part system that's almost like a Christmas light system. A certain code is in the PCM that checks the code in the cluster and key. If the check fails, well then power is cut to the injectors, and the truck will not start.

That is my only personal encounter with the fail, so that's why I believe the PATS system shut off the motor.

 

You can choose to believe whatever you want. I believe I'll believe the manufacturer's documentation on how the system works.

You had a bad power relay, not a PATS problem, that caused the initial stall. The indicated PATS event was a consequence of the initial failure.

 

The system does not work from the PCM back toward the PATS.
The PATS has to be satisfied the correct key code is picked up by the Pats receiver, first.
The translated data signal is transmitted to the PCM over a "dedicated Bus".
The data sets bits in the Identification word IN THE PROGRAM to allow the PCM to start the motor.
This ID word contains more info about the truck as to it's engine size, gear ratio, tire diameter etc.
If there is no match and no bits set, the PCM inhibits fuel.
This is why the PATS, Dash and the PCM all have to match for programing.
I've gone into depth and detail and your not listening!
What do you have to offer as absolute proof that it works differently than just relying on circumstancial evidence of what appear to happen without any background knowledge?
Good luck.

 

Should have said believed, sorry. Regardless, if that's what Ford has stated, then my opinion will change. Can't really argue with the group that built the truck.