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Author Topic: 2500 series Auxiliary fuel tank leak, or?  (Read 312 times)

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CarMech1969

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2500 series Auxiliary fuel tank leak, or?
« on: September 7, 2019, 07:48:32 AM »

Hello fellow enthusiasts  :B:

For the past several weeks or so, I've been noticing a faint gas smell from the left rear area of my 2500 AV.
The smell seems to be getting stronger, so I'm thinking 'what the hell' and decide to take a quick look underneath.
The bottom of the auxiliary tank appears wet, so apparently something is leaking around there.
I'm thinking the fuel lines on top are rusted, but haven't gotten around to pulling the tank to see what is going on.
Any other 2500 owners here had this problem before, and if so, what was the issue?

Thanks for any feedback.

CarMech1969
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Owner of a 2002 Avalanche 2500 series, 4X4

CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #1 on: September 8, 2019, 10:11:17 AM »

Well there you have it, fellas...
Had another look under the truck with a flashlight, and noticed that one of the fuel lines that run from the rear tank to the front (main) tank is wet, so looks like I will have to rip everything out to get to 'em, as the main tank is in the way...Lmao!  :4:
At which point, it will make sense to replace all the lines while I'm in there.
Found a company online called Lines to Go, their prices are quite high though. Quality seems really good however.
Any of you 2500 folk in here have a lead to a good source on new fuel lines? Google turned up not so much.
I could repair what I have, but doubt it's worth the time.
So any leads would be much appreciated.

TIA!! Have a good day  :wave:

CarMech1969

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Randy

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #2 on: September 8, 2019, 23:49:27 PM »

Bummer... I think you can get a complete set from GM and a few others... I would also look closely at the brake lines while you under there and at least replace the lines to the rear while you at if they rusted. A little easier to replace with the tanks out of the way..



https://www.inlinetube.com/pages/product-list?year=8879741983233822622&make=4619135662554405153&model=7070653640939238426

https://www.ebay.com/itm/Fuel-Line-Set-Fits-02-02-Chevrolet-Suburban-2500-Avalanche-2500-FL149-R/273060983896?fits=Model%3AAvalanche+2500&hash=item3f93b3f458:g:pr0AAOSw31hdCUXW
« Last Edit: September 8, 2019, 23:51:05 PM by Randy »
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02 2500 Summit White-Loaded, Heated Leather Seats, Sunroof, Pioneer AVIC-Z3 Navigation System with back-up cam, front cam and Blue Tooth. Nelson Tune, UPD/K&N Intake, Dual Magnaflow SS Mufflers and 3" Tailpipes, Powermaster 225 Amp Alternator, Dual Optima Batteries, Full Traction 6" Lift with 305/70/17 Goodyear MT/R's and SSBrakes, Calipers and Rotors, E-Z Down Tail Gate.

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CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #3 on: September 9, 2019, 03:40:38 AM »

Thanks Randy, I appreciate that.  :thumbsup:
Had a look at their online catalog, and could not find a listing that mentions 2500 or 3/4 ton for fuel lines.
The 8.1 liter engine or auxiliary tank is not mentioned either. So I'm thinking that the link you posted here is for the 1500 AV only.
Brake lines have been changed, they are still fresh when I last looked at 'em.
At this point, not sure what I'm going to do yet.
Lines to Go has a complete kit that includes supply, return, and vent lines for both tanks for the 2500 AV. Free shipping.
Problem is that the kit is upwards of $600.00. Lol! A little spendy, but worth it I suppose.
In any event, I want to make sure that I have supplies on hand before I start tearing into it.

CarMech1969

EDIT: The eBay link you posted is the identical kit that Lines to Go sells - right down to the part number...but it does not ship to Canada....of course....running into this problem constantly when ordering online...lol....always political!

« Last Edit: September 9, 2019, 03:45:51 AM by CarMech1969 »
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Randy

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #4 on: September 9, 2019, 14:40:43 PM »

Yea that's a bit high, did you check the dealer cost?


Try Classic Tube  800-882-3711.. Phone orders get 10% off...
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02 2500 Summit White-Loaded, Heated Leather Seats, Sunroof, Pioneer AVIC-Z3 Navigation System with back-up cam, front cam and Blue Tooth. Nelson Tune, UPD/K&N Intake, Dual Magnaflow SS Mufflers and 3" Tailpipes, Powermaster 225 Amp Alternator, Dual Optima Batteries, Full Traction 6" Lift with 305/70/17 Goodyear MT/R's and SSBrakes, Calipers and Rotors, E-Z Down Tail Gate.

More to follow...

22' Velocity Boat powered by 502 BB and Stage III Procharger 750+HP

CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #5 on: September 9, 2019, 15:02:10 PM »

Yea that's a bit high, did you check the dealer cost?


Try Classic Tube  800-882-3711.. Phone orders get 10% off...

Looked at their catalog online, could not find anything for a 2500 Avalanche.
They do have 2500 Suburban kits though.
Ah well. Thanks anyway!

CarMech1969
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CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #6 on: September 9, 2019, 15:30:20 PM »

 ???
I suppose that I will arm myself with a roll of steel tubing, clamps and a length of fuel injection hose.
Then tear it down and see what I get.
Too many questions, and not enough answers.
Is the top of the fuel pump for the rear tank rotted out? Probably. But won't know for sure until I pull the tank down.
Oh joy....
And even if I want to order a fuel pump for the rear tank just in case, I don't know if it has one electrical connector, or two.
Gotta pull the tank down to see.
 ::)
Another adventure awaits....
Getting old, and not much patience for adventures anymore, lol.
Will take pictures along the way as I get into it.
Surprised that there is ZERO information or pictures about this 2500 Avy stuff....anywhere. Very frustrating.
Guess I'll be cuttin' the road here...
Stay tuned!

CarMech1969
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frito

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #7 on: September 9, 2019, 17:14:38 PM »


Surprised that there is ZERO information or pictures about this 2500 Avy stuff....anywhere. Very frustrating.
Guess I'll be cuttin' the road here...
Stay tuned!

CarMech1969
Any information on Suburbans you might be able to repurpose?
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CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #8 on: September 10, 2019, 04:14:46 AM »

Any information on Suburbans you might be able to repurpose?

I doubt that would work. Too many differences between the two. Gas tanks are different AFAIK.
The thing is that I want to be prepared before I start taking things apart, but the total lack of pictures or diagrams anywhere is going to turn this process into a circus - I just know it...lol.
All one has to do is to look at my thread with the harmonic balancer adventure. Oh boy. Left in the middle of the road, because I couldn't find the tooling needed. Had to get creative!
With the 2500, I suppose it's to be expected. Not so many of them around anymore.
As a result of that, one has to go into a repair blind - no way to prepare for it.
Seems to be the case every time I lay a finger on this truck. Lol!
No choice but to take it apart - and then see how the problem will be solved.
Don't have a second vehicle to use - so this task will have to wait.
Yeah I know, I'm rambling  :P lol
Thanks for chiming in, frito!

CarMech1969
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Randy

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #9 on: September 10, 2019, 11:42:22 AM »

I have some pictures of when I replaced my fuel pump which would show you what the main tank FP looks like. I've never dropped the rear but I may have a diagram of it.. I'm on a new computer and haven't transferred all my files yet from my back up so I can't see what I have right now.. Maybe later today when I get home I can send you something..

I do know that on mine the front tank only has one connection for the fuel pump and sender and the rear has a fuel/transfer pump and the pressure sensor.

There are 3 lines going to the front from the main tank/fuel module ..

1. 3/8 fuel line to the filter, then to the fuel regulator.
2. 5/16 return line back to the tank. If yours has a return line, just look under the hood and you can see it. I think 03 and up may or may not have    the return line.
3. 5/16 purge line to the front of the intake manifold to the purge valve, it's the black plastic line and valve behind the alternator.


As far as the rear tank it has vent lines from the fuel module that connect to the main tank and a transfer line to the main. You will also see the large rubber hose on the bottom front that connects to the top rear of the front tank that transfers fuel by gravity when you fill it.

2500's are rare and a lot of info for the 1500 is the same but not when it comes to the fuel system, rear suspension, transmission and motor..

Good luck
« Last Edit: September 10, 2019, 11:43:56 AM by Randy »
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02 2500 Summit White-Loaded, Heated Leather Seats, Sunroof, Pioneer AVIC-Z3 Navigation System with back-up cam, front cam and Blue Tooth. Nelson Tune, UPD/K&N Intake, Dual Magnaflow SS Mufflers and 3" Tailpipes, Powermaster 225 Amp Alternator, Dual Optima Batteries, Full Traction 6" Lift with 305/70/17 Goodyear MT/R's and SSBrakes, Calipers and Rotors, E-Z Down Tail Gate.

More to follow...

22' Velocity Boat powered by 502 BB and Stage III Procharger 750+HP

CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #10 on: September 10, 2019, 13:43:24 PM »

Thanks Randy, that helps a little bit.
There is a leak coming from the top of the rear tank (hope it's not the pump), and the transfer line has a leak too.
The thing that is bugging me a little bit is that there are two different fuel pumps for the rear tank, apparently. Lol. At least that's what RockAuto shows.
So I won't know which one to order until I pull the tank.
Then, when I pull the rear tank down and it turns out my fuel pump is rotted out - I'm gonna have to MacGyver something, or else I can't drive.
Keeping my fingers crossed.

CarMech1969
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CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #11 on: September 10, 2019, 13:52:05 PM »


You will also see the large rubber hose on the bottom front that connects to the top rear of the front tank that transfers fuel by gravity when you fill it.


Hmm, that's interesting.
If fuel is gravity fed from the aux tank to the main tank, then what is the point of having a fuel pump and transfer lines on the aux tank?
Seems over-engineered.
Lol!

CarMech1969
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Randy

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #12 on: September 10, 2019, 16:12:06 PM »

Yea I'm not exactly sure how it's engineered to function.. I would look at the service manual but I just moved a few months ago and still have not unpacked all of the garage stuff.

I should change when I said the outlet is at the bottom of the tank, it's near the bottom so all of the fuel is not gravity feed to the main tank so the rear tank pump comes on when the rear float hit a certain point and transfers the remaining fuel to the main tank. I think the main tank fuel level has to be at a certain level also before it comes on.. My guess for now, but it would have to have room for it. I think that's why you can drive so far on a 1/2 tank then it drops faster the last 1/2, at least that's the way mine is..

I've always thought that you would never know if the rear pump went out because most of the fuel drains from the tank. I guess if your mileage dropped all of a sudden and you fill up was less than normal when you fill from empty you might figure the rear pump is not working.

Edit..

If your going to be working on the AV yourself a lot, them if you don't already have the service manuals then you should pick up a set.. They are not cheap (usually $200-$400), there's a set on ebay right know for $147 plus shipping.. Makes it a lot easier to figure things out..

https://www.ebay.com/itm/GENUINE-2002-Chevy-Avalanche-Suburban-Tahoe-Denali-Service-Shop-Manual-4-Vol-Set/362676791562?hash=item547138a90a:g:8SoAAOSwTU5dA~Yp
« Last Edit: September 10, 2019, 17:11:21 PM by Randy »
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02 2500 Summit White-Loaded, Heated Leather Seats, Sunroof, Pioneer AVIC-Z3 Navigation System with back-up cam, front cam and Blue Tooth. Nelson Tune, UPD/K&N Intake, Dual Magnaflow SS Mufflers and 3" Tailpipes, Powermaster 225 Amp Alternator, Dual Optima Batteries, Full Traction 6" Lift with 305/70/17 Goodyear MT/R's and SSBrakes, Calipers and Rotors, E-Z Down Tail Gate.

More to follow...

22' Velocity Boat powered by 502 BB and Stage III Procharger 750+HP

frito

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #13 on: September 11, 2019, 08:48:46 AM »

Hey CarMech1969, sent you a PM.
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CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #14 on: September 12, 2019, 03:56:35 AM »


I should change when I said the outlet is at the bottom of the tank, it's near the bottom so all of the fuel is not gravity feed to the main tank so the rear tank pump comes on when the rear float hit a certain point and transfers the remaining fuel to the main tank. I think the main tank fuel level has to be at a certain level also before it comes on.. My guess for now, but it would have to have room for it. I think that's why you can drive so far on a 1/2 tank then it drops faster the last 1/2, at least that's the way mine is..

I've always thought that you would never know if the rear pump went out because most of the fuel drains from the tank. I guess if your mileage dropped all of a sudden and you fill up was less than normal when you fill from empty you might figure the rear pump is not working.


Last time I bought a manual for anything was nearly 30 years ago  ;D

I suspect that you are correct on the fuel tank operation. Mine also sits at about 1/2 tank for an extended period, and then suddenly drops. It also makes sense that all supply/return fuel lines are at the top of the rear tank. If they were at the bottom, you'd have an awful mess if any of them started to leak! It'd be dangerous, too. So I can see the logic in that idea.
In my opinion, it would have been better if they made the rear tank larger. 6 gallons isn't all that much. But I think we know why it was done the way it was. Lol!

CarMech1969
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CarMech1969

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Re: 2500 series Auxiliary fuel tank leak, or?
« Reply #15 on: September 12, 2019, 03:57:22 AM »

Hey CarMech1969, sent you a PM.

Thank you sir!
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