2000 Silverado Random Stalling

[mfarmdawg]

I tried a search first and didn't find what I needed....

I bought a 2000 Silverado 4.8 and Auto trans with 244K miles on it for my son's first vehicle. Everything was going well for a few weeks and on Thanksgiving Day it started randomly stalling. No pattern, not only when warm or cold, no SES or Security lights on the dash for the most part. Sometimes it will stall right after starting, sometimes it will run fine for days and then randomly stall. So far we've replaced the ignition switch, the ignition lock cylinder, fuel pressure regulator, the Evap canister, the purge solenoid on the manifold, checked fuses, relays, fuel pump pressure (stays at 50psi, drops to 46 after the engine stops and then climbs back to 51), it still has the same issue. I believe the fuel pump was replaced as well as the evap canister and possibly the vent valve solenoid before by the previous owner. The bed bolts are somewhat loose and you can see the wear spots from original install from the bed going back on. I'm at my wits end with this thing. I'm afraid for him to drive it like this and the possibility of it leaving him stranded in the middle of an intersection or causing an accident.

Please help?!

[EVRLET]

I What’s the battery voltage on the dash reading? I have a 2001 Silverado 4.8 and I started to notice stall problems when I hit the remote start. It would start and run and then die. The remote start started it back up and it would either run good, or it would stall again.

I noticed when I drove around town, there would be days with no issues. The days when I had stall issues, by the time I got home or wherever I was going, I noticed my battery voltage was below 10v. I determined my alternator was intermittent and was slowly dying. Replaced it with a bigger alternator from a 6.0 and all the stall issues, even with the remote start, was gone and never came back. Month into alternator replacement and hasn’t stalled once.

These LS and all computer controlled engines are very strict to voltage levels.

Just a thought...

[mfarmdawg]

This truck doesn't have remote start that I know of, I have considered having the alternator tested but haven't gotten that far yet. From what I've noticed with the voltage, it stays about 13-16 volts while running. The only light or indicator that we get when the truck does stall is the battery light comes on to show the engine isn't running. Not knowing the history of the truck, I can only guess as to what it's been through and had replaced...it makes it that much more fun to work on. We've replaced parts that seem to be not that old a few times so far...

[95 S_Trucker]

Fuel pressure is low. It should be 55-62.

When does it shut off? Is your foot on the gas, is it off the gas. At a certain speed?

[mfarmdawg]

It's all of the above. It will stall when it's idling, it will stall stepping on the gas to leave a parking lot or intersection, or coasting. Like I said there's no particular pattern to it or certain time frame when it does it. Sometimes it stalls right after start up, sometimes after it's been driven for an hour or even a few minutes. Some days it runs with no issues and then randomly stalls after a few days of moving it around.

[EVRLET]

The remote start is a part of my aftermarket alarm system. Since you need air/fuel/spark to run an engine, let’s start there.

- Is there build up in the throttle body? Try spraying some throttle body cleaner in there and clean up the airway.

- Clean MAF sensor with MAF sensor cleaner.

- You didn’t say if you changed the fuel filter. If you didn’t, change it.

- Since you don’t have any codes, we can assume for now that your coil packs and spark plugs are good. If they weren’t you would get misfire codes.


Other issues:

- Catalytic converters clogged? How many miles do you have? If you’re in the high 100s, you might want to consider that.

- Get your alternator tested

- Any vacuum leaks?

[hatzie]

A good working fuel pressure regulator hangs right in at 58PSI. 50 is too low. Low fuel pressure will cause intermittent hard starts and random stalling.

Either the fuel supply is restricted or something in the fuel supply/pressure-regulation side is failing.

Change the fuel filter on the LH frame rail. This will eliminate the filter as a possible restriction. It's cheap and it's probably never been changed.

If the fuel pressure doesn't come back up with a new fuel filter the fuel pump and or fuel pressure regulator are failing. One or or both...

The Delphi FP10021 fuel pressure regulator is not expensive and it's fairly easy to change. At over 244,000 miles it's no longer in its' first flush of youth so changing it will not hurt anything.

If the pressure is still hanging at 50psi after the filter and FPR are changed then it's likely the fuel pump... Again not shocking if it's the factory original part at 244,000 miles. The original equipment Delphi sender/pump assemblies are going to last the longest but they cost a pretty penny.

I don't like disturbing things that are better left the way they sit. The fuel tank is one of those things. I always pull the bed to do the fuel pump and sender assembly. Don't ever use power tools on the bed bolts and be sure to slobber em up with never-seize when you re-install em making sure to put some inside the captive nuts as well. The taillamps just unplug on the frame and the filler neck un-bolts from the bedside.

[mfarmdawg]

Thanks for the recommendations! I will start with the MAF cleaner and the fuel filter. I have replaced the fuel pressure regulator with an AC Delco part for it. We seem to keep changing parts that have been done already as we chase this issue down. It's hard to know for sure, but I believe the pump was changed once already and they removed the bed to do it. I will check the alternator, but I do't think that is the issue either. I started it and drove it the other day and the gauge on the dash indicated it was running at 18 volts to recharge it after sitting for a while then dropped and held at 16 volts once it had been driven for about 15 minutes. I'll also re-check the fuel pressure before and after the fuel filter change to see what if any changes result.

One final note, I'm not sure this is completely accurate, but when the fuel gets down to 1/4 tank or lower, we don't seem to have issues with it stalling. Once I filled the tank for the first time since buying it is when we started having issues. We've driven it for a while now between the stalls and it's back down to 1/4 tank. Drove it to and from work a couple of days ago with no issues....maybe nothing or it may have some relevance.

[EVRLET]

It looks like you have quite a few paths to go down.

I truly believe the 1/4 tank issue is a clue. It’s a possibility that maybe the previous owner didn’t install the pump right or maybe left off the fuel screen. If after everything and no progress, it might be worth getting into the fuel tank and taking a look. I mean, that’s where the fuel starts and apparently the fuel level potentially plays a factor.

Let us know what you find and don’t leave us wondering what the solution was.

[mfarmdawg]

So after a few days of bad weather and other things keeping me away from the truck, I finally got back to it this morning.

Checked the MAF and throttle body, both were pretty clean. Sprayed the MAF with some cleaner anyway.

Checked the fuel pressure again and with it running it stays around 50psi at 40* outside this morning. Read the Haynes manual for fuel pressure specs and saw it's supposed to be 55-62 like mentioned earlier and it needs to be checked with the key on/engine off. Did that and while the pump is running for the initial key turn, it stays at 58. The pump only runs for about 3-5 seconds and then stops and the pressure drops to 50-54 when that happens. Turning the key off sees the pressure drop to 44. Changed the fuel filter and saw very negligible change. Turning the key to the on position and the pressure jumps to 58 while the pump runs and then levels back off to 53-54 when the pump shuts off after initial charge. Running the pressure stays at 50psi. Shut the key off and the pressure drops to 44 and stays there. Soooooo...... I guess we're going to be trying to remove the bed and replace the pump. Wish us luck, the passenger side of the bed has two of the four bolts half way out already like someone cross threaded them and they got stuck or stripped the caged nuts and couldn't get them all the way back in.....

[mfarmdawg]

Update:

replaced the fuel pump and what we took out looked pretty damn new....now we have a lifetime warranty in our name though if nothing else for peace of mind. everything is exactly the same as it was before swapping out the pump. Runs and holds 50psi pretty consistent with the engine running. First turning the key without starting the engine shows 58psi for the three seconds or so as the fuel rail re-pressurizes then it drops to 52 and holds there with the engine off. The fuel pressure regulator was changed out for a new Delco part about a month or so ago and it didn't change anything. I hooked up my fuel pressure guage to a buddy's truck with an LS3 transplant and an aftermarket fuel pump and saw 46-49psi while it was running and similar stats as mine with the engine turned off but key on.

So we've replaced about all we could with the fuel system, and most ignition components that we could....if it still stalls, I have no idea what's going on other than a faulty VATs or PCM.

[406flyfish]

Check the ecm ground wire it’s on the back of the passenger head. Give it a good tug if it’s bad it will break.

[mfarmdawg]

From the appearance of things, we think we found the problem. The ground connection where the fuel filler neck ground connects to the frame has two large wire looms connected as well and the connection was rusty and corroded. We cleaned it all up before putting it back together after replacing the fuel pump and it's been fine since then.

[EVRLET]

Glad you found the fix. Appreciate posting the end results to help others.

[hatzie]

Just like gramps said. Check your grounds...
Thanks for the After Action Report.