Fuel Issue. I'm miles away and preparing for likelyhoods.

[89RagTopRS]

Okay, here's the specifications: 2002 GMC Yukon XL 1500 4wd 5.3L Flex Fuel. 182k miles. Spotty to nonexistent service history outside of my own. Brand new transmission with shift kit, valve body and all the other things GM should have done factory, flex fuel bypass since it will never see E85 and the sensor is bad. Engine code is downdraft O2 sensor failed (bad wire I'm still tracing as the sensor is new). The price was right and I knew what I had even though I haven't found all of the problems yet.

The truck has suddenly been tasked with doing 70 mile hauls every 3 days or so with some weight and no towing. I personally have had zero issues with it. I have thousands of miles on it. I was a passenger in the truck the first time it stalled out seemingly out of nowhere less than 2 miles from our destination 7 days ago. I know it is not a ghost issue as I've witnessed it. I drove it back 2 days later without issue. The other drivers often hit 3000+ rpm at acceleration where I almost never exceed 2000-2500. The highway doesn't count as far as top speed rpm. There has been issues where it took 2-5 minutes to get it restarted and an issue where the throttle had to be to the floor to get it restarted.

I'm 60+ miles away and the crew on site is going to change the fuel filter that is of unknown condition or mileage. They have no way to test fuel pressure on site without me and I'm 4 days away at minimum. I'm going to have a fuel pump shipped to site. What else part wise besides my trailer would you recommend as I'd just assume tow it back with my Sierra than pay $500+ to bring it back with a towing company?

I'm just learning all the issues with the Vortec LS engines and that generation truck series as I'm familiar with the older models and the old Nissan Z24 engines. I'm leaning towards pump first and regulator second, but what are the odds it's one of fuel injectors is stuck open?

 

[iamdub]

Did you mean that you had the codes read since this happened and that downstream O2 sensor failure was the only code or did you mean you had it read in the past and that's what you got?

Also, what lead you to the conclusion that the current stalling/no start issue is a fueling issue?

 

[89RagTopRS]

The O2 sensor was a previous ongoing code. I've done everything short of running the wires all the way up to the harness. I have my code reader at home, not where the truck is. I'm starting fuel related issue based upon asking multiple GM techs I know and the fact my old Camaro had this very same issue and symptoms when it was also around 15 years old too. The reading I've done since this post last night also confirm fuel delivery is the most likely target to begin looking. Especially since it can be difficult to restart without time passing, fiddling with on/off switch to boost fuel pressure and so on. The lack of service records with the truck also leads me to believe it saw a lot of less than 1/4 tank running. A worn out pump from heat is not unreasonable.

 

[iamdub]

There may be other codes. An illuminated CEL is an illuminated CEL. It may have come on originally for the O2 sensor circuit, but other codes may now be present and you won't know until you scan it again.

I'm not discounting this as the problem, but low fuel level in the tank shouldn't be a problem. These pumps are inside a bucket that stays full regardless of the level in the tank. Well, it should unless it has a leak.

 

[89RagTopRS]

I'm sure that when I run the reader when I finally get there I'll find just the O2 sensor failure. Just like the last time I ran the test an hour after my own experience with the stall out. Rather than an inquisition I cannot answer from 70 miles away from the machine, what other potential and common issues with these trucks am I missing with symptoms resembling what I describe? Is there something I may be overlooking. I'm trying to plan a course of action that may involve me buying more than I need, but I'd rather not be without. There are zero auto parts stores within 10 miles and the ones on the outskirts I'm willing to bet their stock situation is less than ideal. I have 2 days to travel, diagnose, fix, get my work done and then drive it back. Normally, those 2 days only cover travel and getting my work done.

 

[iamdub]

My guesses are flooding due to leaking injector(s), a dying fuel pump, a poor ground or other wire connection in the fuel pump circuit (these things are known to have crappy grounds and the power wires for the fuel pump are marginal at best when new), a sensor intermittently giving the PCM false info (such as TPS telling the PCM the throttle is at X% when it's actually at X%), loose wire connection in the key cylinder (wiggle the key while driving to see if it shuts off), loose battery terminals or otherwise poor battery circuit (check all cables for clean and solid connections), bad battery (internal cell intermittently opening- these trucks won't run "straight off the alternator")

Maybe bring a battery in addition to the new fuel pump? Or have the guys swap it for a battery in another truck and see if the problem follows?