2003 Yukon - 26 gallon tank, but runs dry after 20?

A

Atrus

Forum Member
You guys and gals have a wide variety of experience, so I am interested to hear if you've experienced anything like this. I recently picked up a 2003 Yukon 4x4. It's relatively clean, has 122k on it. It's the 5.3L "Flex Fuel" engine, and has a 26 gallon tank. I have replaced the fuel filter already.

Twice now I have inadvertently run the tank down to empty, to the point where it won't start. The gas gauge gets darn near E (not at/past E though), but no low fuel light comes on, nor does the DIC tell me it's low on fuel. The DIC seems to be reporting accurately on everything, except is still shows large range when it craps outta fuel. For example, this morning I accidentally ran it to 0...when I went out to go to work, the truck wouldn't start and it showed 90-100 miles left of range.

The weird thing to me is...despite being bone dry twice - or at least, so low the pump couldn't supply fuel - I can only cram 20 gallons into the tank before it's completely full. Not that it's good practice to, but I would expect to have at least 24 gallons of usable gas should I choose to run it down that far.

Any thoughts? Fuel pressure itself seems good. I have gotten an intermittent P0300 when I am doing 80+ on the eway, but it runs fine. When it has gas in the tank, it fires up right away and smoothly be it warm or cold. It's almost like the pump is hanging too high in the tank, but the fuel sending unit is actually reporting properly.

I have no way of knowing whether the pump was ever replaced, but I doubt that it was.
 
Thinking someone put in the smaller tank on you instead of forking out the money for the bigger tank...
 
I don't think they ever came with a 20 gallon tank though. 26 in the regular Yukon/Tahoe/Escalade and 32 in the Yukon XL/Suburban/Escalade ESV.

I did read a thread on a truck forum talking about how a guy's Tahoe would run past 1/4 tank if he didn't shut it off, but it was unable to start at under 1/4 tank due to a weak pump trying to prime itself on a low fuel level. Sounds similar to what I have going on...except mine isn't as bad as 1/4 tank, it's more like 1/16 tank per the gauge.

Maybe I'll just suck it up, drop the tank, and throw in a new pump & sending unit. Seems like I should be able to do that for ~$200 and a 6 pack.

Posts #8, #9, and #11: http://www.gm-trucks.com/forums/topic/110786-2002-tahoe-wont-start-with-less-than-14-tank/
 
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it seems like this is a very common thing with GM vehicles.. my 2014 silverado has the 26 gallon tank it it. just filled it up today when it was BELOW the E mark. 22 gallons.

my old duramax's all had the same problem. run it until the light came on. then another 20 miles. and still fit 20-22 gallons in a 26 gallon tank
 
My 2014 Sierra was similar in the fact that it would run down to 0 and I'd still have several gallons left. I had put up to 23-24 gallons in that thing before. Difference here is the vehicle is still showing I have fuel, but it's dry or low enough the pump can't supply fuel, and then I can only fit 20 gallons in.
 
I had a 03 silverado where on a couple occasions I went till the low fuel light came on (no DIC message display thing on mine). Went less than 5 miles and put just over 26 gallons in a supposedly 26 gallon tank.

Maybe somebody put a pump in it before but it was the wrong pump and its too short?
 
I've got a 2004 Tahoe z71 Flex 5.3L w/ 150k. The tank may be rated at 26 gallons, but a normal fill up when running on fumes is 22-24 gallons. And given the way the evap works on these tanks, you don't want to overfill or try topping it off.

My guess is the fuel pump assembly is going bad. My original pump died at around 140k miles and a couple mechanics I spoke to were amazed it lasted that long given the history of fuel pumps on the GMT800s. In my case, the pump started making a metal-on-metal grinding/squealing noise that resonated up the fuel lines that actually made the sound appear like it was coming from the metal fuel cross rail on top of the intake manifold. I think I posted a thread in the Tech Help section here. I couldn't figure it out 100% until one day, I came out to start the truck, no start with plenty of gas in the tank, and a simple tap of the bottom of the tank with a hammer while someone else keyed the ignition immediately solved/confirmed the problem. I got a replacement Delco pump (#MU1378) from AAP who had it in stock for $250. The Delphi equivalent unit is a bit cheaper (I wouldn't go with any other brands!). I did the replacement on the floor of my garage - not fun - took me a weekend but I did a very thorough job (dremeled the lock ring area clean, douched the tank, etc.). Rust is the biggest problem - the rear left tank strap bolt is a PITA (caged nut often breaks off, or bolt has to be sawzalled), and the pump lock ring area was totally rusted and had to be cleaned up to even get the new replacement lock ring to function. My lines had already been replaced (Thanks Rich!), so that wasn't an issue for me, but could see if yours are original, there may be some challenges there too.

Also, the stepper motors in the IP of these trucks are also known to fail. Usually the tach or speedo go first. I could easily see the fuel tank level stepper/needle either failing, or someone hacking in the replacement and failed to keep the fuel level needle pointer calibrated. But some of your other symptoms seem to exclude this, making the pump most likely IMO.

And also beware that the intake gaskets on these trucks are commonly known to leak in the cold months and need replacement. It'll throw codes intermittently for lean bank 1/2, and MAF. Go with the nice Felpros (#MS98016T, < $50). Not too bad of a job (easier than the fuel pump IMO) - took another weekend, but much of that time was cleaning stuff.
 
Thanks, Killjoy - that really helped confirm my thoughts. I am thinking the pump is on it's way out. Seems logical that a weak pump/dirty screen on a pump may prevent it from starting up once the fuel level has dropped. Also makes sense that it drove perfectly fine when I parked it last - it was already running when it hit that lower fuel level, so it wasn't as much of a strain to start.

I appreciate you bringing up the intake gaskets - I was aware of that as well. I plan on doing them as preventative maintenance once the weather is decent. I've done them on my LS1 F-body, so I think/hope this shouldn't be any worse.

Now the question is - do I want to spend the time trying to do the pump myself, or should I farm it out?I hate to spend the money, but I really don't think I feel like taking this one on myself.
 
You can see what you're getting into from the pic below. FWIW - the inside of my tank was extremely clean for being 12 years old. And I'd have to assume that the majority of the rust "dirt" that was in there was likely from me beating on the damn lock ring for over an hour to get it off. You can see in the pic below how clean the filter screen was (that's how it came out of the tank) and what a rusted POS that top lock ring was. The rust literally welded the ring to the metal fingers on the tank. Make sure you buy (or tell the shop to use) a new lock ring on the new pump.

IMG_3388.jpg

I spoke to a couple shops about doing the pump for me, and both wanted ~$800. It was basically $400 for the pump, $350-400 in labor. I said screw that, got the OEM Delco pump for $250 using a discount code and killed a weekend instead. If you can find a less formal shop that'll let you BYOP and just charge you labor, that's the way to go IMO.

I called around on the intake gasket job too - estimate was $400. I just picked the Fel-pro's from Amazon for $45 and made a weekend out of it. You could easily do it in less than a day.... probably 4-6 hours as a DIY... but I also took people's advice and replaced both knock sensors (only use Delco!) + pigtail while I was in there, and added the TSB-suggested RTV protection around the knock sensor openings. In reality, I spent more time cleaning stuff than actually wrenching.
 
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Thanks for the head's up on the ring. I am really torn on this. My old man had the pump in his '99 Tahoe done at the stealership this past summer....$800 in labor and roughly $300 for the pump.

I will call a couple local shops to get labor estimates. I can get the pump for $180 off Amazon - a good Delphi pump. I agree, Delco/Delphi only. I am starting to think I may tackle this myself over an upcoming weekend. Seems like I should be able to get it done in 1 day.

Thanks again for the info - I surely hope my lock ring doesn't look like that. Was this with 300k+ on it? I'm at 122k and am fairly impressed with how clean the chassis seems to be. The frame has flaky rust on it, but I pulled the front driveshaft to get to the B1S1 O2 and it came apart easily. The suspension bolts and everything look relatively decent, just surface rust.
 
Atrus said:
Thanks for the head's up on the ring. I am really torn on this. My old man had the pump in his '99 Tahoe done at the stealership this past summer....$800 in labor and roughly $300 for the pump.

I will call a couple local shops to get labor estimates. I can get the pump for $180 off Amazon - a good Delphi pump. I agree, Delco/Delphi only. I am starting to think I may tackle this myself over an upcoming weekend. Seems like I should be able to get it done in 1 day.

Thanks again for the info - I surely hope my lock ring doesn't look like that. Was this with 300k+ on it? I'm at 122k and am fairly impressed with how clean the chassis seems to be. The frame has flaky rust on it, but I pulled the front driveshaft to get to the B1S1 O2 and it came apart easily. The suspension bolts and everything look relatively decent, just surface rust.
Click to expand...

Man do I hate to have to tell you this.....Did the fuel pump on my southern 2005 Tahoe, my tank lock ring
looked worse than the one in the photos above, and furthermore, my metal lines (elbows) on the top of the pump
were rusted through. It was the leaking lines that was why I had to change my pump & not pump failure.

Remember, this was a southern nearly rust-free body truck and the poor design on that pump (it is recessed
and simply holds water & crud to riot). All in all, the replacement wasn't too bad of a 1 day job. As others have
said, make sure you buy new lock ring.
 
4Gas$ said:
Man do I hate to have to tell you this.....Did the fuel pump on my southern 2005 Tahoe, my tank lock ring
looked worse than the one in the photos above, and furthermore, my metal lines (elbows) on the top of the pump
were rusted through. It was the leaking lines that was why I had to change my pump & not pump failure.

Remember, this was a southern nearly rust-free body truck and the poor design on that pump (it is recessed
and simply holds water & crud to riot). All in all, the replacement wasn't too bad of a 1 day job. As others have
said, make sure you buy new lock ring.
Click to expand...

Damn the man - thanks for the warning. Better to be prepared. I will definitely have a new lock ring on hand to replace the original.

I also do plan on replacing the entire pump/float assembly, so even if the metal lines are shot they'll be replaced. Looks like the lines that run along the top of the tank are plastic.

The good news is (knock on wood) it seems to be running really well for now, so I am hoping I can hold off on replacing until I have a free weekend and some favorable weather. I'll just have to be prepared that it can die anytime. I work 16 miles from home, so worst case it dies, I have the wife come out to get me in her car, and I use her AAA card to get it towed back home.
 
I don't know how much different a 2003 GMC Sierra set up is then a Yukon. I changed one a few months back it was pretty easy. The lock ring had some rust but it wasn't terrible. I did have to replace the gas tank straps one of them broke due to rust. It took me less then 2 hours start to finish.
 
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Nice! I can deal with a few hours. I would like to take the time to clean out the tank properly too, just to ensure no future problems.
 
Atrus said:
Was this with 300k+ on it?
Click to expand...
Ha! Try 140k miles.

All I'm going to say is.... Plan for a full day short of having a hoist, an extra set of hands, and a trans jack or something else to manhandle dropping/raising the tank. Both fuel lines must be disconnected blind. And that rear tank strap bolt is a 50/50 sawzall deal depending on rust level. With no rust, I could see this as maybe a 2-4 hour job. If it's a MI truck, you're going to have 2-4 hours of PB Blasting shit before you even get started.

The lines that connect to both fuel pump pipes are plastic and run a few feet to the front of the tank. That's where they quick connect to the metal lines, and where you should disconnect for dropping the tank. But as I said above, it's all gotta be done blindly. My lines were only a couple years old and no rust issues... but if yours are original, I could easily see breaking one doing this job. Rust eats the brake and fuel lines of these trucks like cancer - another well known issue. These were mine before replacing them all:

IMG_1780.jpg
 
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I've read that the sock can be the problem....if I get in there, though, I am just replacing it all. My luck I'd replace/clean the sock, and then a week later the pump would actually shit the bed. I can get the new Delco pump and locking ring off Amazon for $200.
 
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