Help me I'm stumped. Truck died and will no longer run.

[MOBS]

^Good info there....but could it possibly be a partially stuck-open FPR?

 

[Aloicious]

^Good info there....but could it possibly be a partially stuck-open FPR?

theoretically, sure....but statistically unlikely, I've never encountered a vortec with a stuck open FPR enough to cause the poppets not to open, I've seen the FPR leak a little, but if its leaking that much pressure off into the intake, you'd get hydrolocked before anything else (the FPR on a vortec is part of the fuel injetion spider inside the intake manifold)....and also considering the scenario he describes is an extremely common scenario for fuel pump failure in the 96+ GMT400's....the odds are heavily stacked in favor of the fuel pump being the problem...

 

[MOBS]

Ah I see....well, here's a recommendation....switch to direct injection! Hope ya figure out your problem man, if it's poppets, upgrade to the other type injector spider(forgot what it's called).

 

[Aloicious]

there you go! heh...I would LOVE to see a direct injection SBC

yeah, the poppets aren't faulty by not opening, unfortunately they're designed not to open unless you're running at full pressure. I'm 99.72% sure its the fuel pump....

it wouldn't be as much of an issue if the vortec used real injectors that were fully electrically controlled....in fact I had a fuel pump failure after I swapped to real MPFI setup, the pump died while driving home from work, it would only output 11psi (I have a FP gauge mounted in my overhead console, and my regulator is set at 45psi, so it would barely idle but not for long since it was only getting 1/4 of the fuel it was expecting)...but the 11psi it output was somewhat consistent, so I just pulled out my laptop, re-tuned the truck for the lower pressure, and it drove home just fine...thats one of the good things about real injectors, they're fully controlled by electricity, they don't require a signal AND proper pressure to open like the poppets do....

 

[CajunGMC]

K.I.S.S. Try a bottle of heet first. OP stated outside temps at o* to 30* Water in fuel will freeze at these temps. Wife's van did this last winter. My truck 2 winters ago. Place fuel down the throttle, if truck runs then dies, check for frozen lines first. If the heet doesn,t work, then follow all the great advice posted above. Good luck.

 

[borahshadow]

Aloicious. Changing the fuel pump isn't something that I'm particularly excited about, but I'm glad that I most of us are in agreement about it. Like I said I too thought it sounded like the truck was starved for fuel.

I'm out of town for one more day before I can get home and put some gas in the intake and check the fuel pressure. Assuming that it is the fuel pump I've got some questions.


First, Is a stock replacement something that I should use or should I use an upgraded unit? I would love to do a 6.0 (or maybe 5.3) swap when my L31 finally dies (hopefully not for at least 20-30k more. Is a stock replacement acceptable for a Gen III motor? If/when I do a 6.0 swap I'm probably going to keep it pretty stock. I'm not planning any wild mods for my future engine.

Second, How is the easiest way to change the pump? I've heard of people taking the bed off to get to the top of the fuel tank to change it out and I've also heard of people dropping the tank out of the truck to get to the pump.

I guess if I took the bed off it would be a good excuse to treat the frame rails with something...

K.I.S.S. Try a bottle of heet first. OP stated outside temps at o* to 30* Water in fuel will freeze at these temps. Wife's van did this last winter. My truck 2 winters ago. Place fuel down the throttle, if truck runs then dies, check for frozen lines first. If the heet doesn,t work, then follow all the great advice posted above. Good luck.

The day that it finally died it was closer to 40. I then put in in my shop which was above freezing so I think that if if anything was frozen up it would have thawed out by then being in my warmer shop and all.

 

[Marcos]

I always change the fuel pump by taking the bed off, 8 bolts and unplug the taillight harness, 2 people and walla easy access to the fuel pump.

 

[sewlow]

Yup! Remove the box. A LOT easier than fighting a 1/2 full tank & that damn filler neck. With the box on, it's an exercise in frustration. Change the fuel filter on the frame, too, while you have the box off.

 

[bluex]

I got my FP test kit at harbor freight for under $30 if I remember right. I had a 20% off coupon too though.

Here is one, but it isnt the one I got:

http://www.harborfreight.com/automo...r-fuel-injection-pressure-test-kit-97706.html

This is the one I got...

http://www.harborfreight.com/automotive-motorcycle/diagnostics/fuel-injection-pump-tester-92699.html

 

[Aloicious]

Aloicious. Changing the fuel pump isn't something that I'm particularly excited about, but I'm glad that I most of us are in agreement about it. Like I said I too thought it sounded like the truck was starved for fuel.

I'm out of town for one more day before I can get home and put some gas in the intake and check the fuel pressure. Assuming that it is the fuel pump I've got some questions.

First, Is a stock replacement something that I should use or should I use an upgraded unit? I would love to do a 6.0 (or maybe 5.3) swap when my L31 finally dies (hopefully not for at least 20-30k more. Is a stock replacement acceptable for a Gen III motor? If/when I do a 6.0 swap I'm probably going to keep it pretty stock. I'm not planning any wild mods for my future engine.

Second, How is the easiest way to change the pump? I've heard of people taking the bed off to get to the top of the fuel tank to change it out and I've also heard of people dropping the tank out of the truck to get to the pump.

I guess if I took the bed off it would be a good excuse to treat the frame rails with something...

yeah, you can do either, but I prefer removing the bed like was mentioned. if you don't have someone to help you lift the bed off the frame, I've used a cherry picker engine hoist before to lift it off....its really not too hard a job once you get into it, it just seems daunting, I know how you feel, I had to replace mine last time outside in subzero weather...I hate the cold...

the stock pump is a good pump IF you use a delco/delphi brand....any off brand/store brand assembly will not last, and you'll be replacing it again soon....the stock pump will feed a genIII engine just fine. it will actually feed quite a bit of horsepower very well and there are some things you can do to increase their longevity, such as replacing the fuel filter routinely (I replace mine ~1 per year, usually in the fall when I change the oil.), also don't let the fuel in the tank drop below 1/4 tank if you can help it, the pump uses the fuel in the tank to cool it, if you regularly run the tank really low it can cause the pump to overheat at those times and shorten it's lifespan.

you'll want to replace the whole sender/wiring harness assembly, which will come with the stock pump, these trucks had an issue with the wiring corroding and melting, as well as the sender wearing down and causing wierd artifact in the fuel gauge needle reading, even if you don't have problems with the gauge now, it'll likely happen before you need to replace the pump again, the little contacts within the sender are mechanical and wear out over time....in fact if you want a funny video of what my fuel gauge was doing when my sender started having problem, check this out, the video quality isn't great, but if you also look at the oil pressure needle below it, every time that one twitches, the fuel gauge is swinging around and hitting it, its like watching a lightsabre fight at night with my LEDs on:

http://s461.photobucket.com/albums/qq337/guitargeek1968/?action=view&current=Insanefuelgauge.mp4