(Note: I posted this on another forum as well, trying to get as much info as I can about this while I try to solve it.)

Anyone have any suggestions?

 

Look above the driver side front wheel well. You'll see the PCM (ECU) mounted in a slot in the firewall. Disconnect the wiring harness plug (8 or 10 mm bolt I think) and take off the two nuts or bolts that hold the thing in there, then slide the module out. To get it completely out you might have to take out a few of the bolts holding the plastic wheel well liner in and pull it down a bit to make room.

 

Test that pump first! Sounds more like pump failure than ECU failure. Test connector has provision for pump test.

 

x2 ... and if the fuel pump checks out ok then start looking for spark.

parts tossing is the least efficient, and most expensive trouble-shooting method there is.

 

Jumpering the fuel pump resulted in the pump running just fine immediately after the incident, so I am inclined to think it's less the pump.

After letting the truck cool off completely and coming back to it, we were able to drive it to my friend's place okay, but the truck started trailer hitching again under moderate to heavy acceleration (which it had started doing a couple days ago). Luckily I was able to get it to his place before it started conking out all the time.

 

OP wasn't able to get a system pass code from his PCM. That's a common symptom of PCM failure however from what I've read usually the fuel pump stays running instead of not working at all.

Could also just be faulty wiring or a bad ground point.

 

I did not see where he checked the codes.

But it sounds like the computer lost its ground at the NEG post of the battery.

But I have seen on here where the computer has stopped the fuel pumps from running with no injector grounding. This happens when the computer lets out smoke most of the time.
That does not sound like the case here but I would guess a bad computer and I do not think replacing the caps will help this one.

 

After limping it back to the shop (nice and quiet since it was after regular hours) I was able to start checking things over. With the truck turned off, I began by starting from basics - running the wiring harness to check for breaks, shorts, etc. When I physically bumped the ECU relay, I heard a sloshing noise and the clicking of other relays. Yup, ECU relay was full of water, which would account for the ECU not displaying codes or illuminating the check engine light when examined right after stalling - it wasn't getting power. The water heating up, flashing to steam and cooling back down would account for it being able to restart after a period of time had passed. Replacing the relay eliminated the stalling issue even after being at full operating temperature for long periods of time.

However, I've still got a 'hitching' or misfire issue occasionally under load/acceleration. Here's a video of it; that's foot flat to the floor once I start accelerating, I'm not letting off through the end of the video.


It occurs to me that despite all the other work I've done with the truck since I got it, I somehow neglected the plugs and wires. I also have a new coil I bought 'just in case' earlier when RockAuto was having a sale. I think I'll do those first and see if it's still there after - should that be the case, any suggestions as to where I should look next?

 

Just to close this for the archives, the hitching problem turned out to be the low pressure fuel pump in the tank.