Yukon XL aux. fuel tank operation

swathdiver · September 17, 2018

7 hours ago, superdeeduper said:

2500

Thanks. Was wondering if your secondary tank was stock (2500) or added (1500).

corvairwild · November 18, 2018

I just purchased a 2001 Suburban 2500-4x4 6.0L in Hemet California. I drove it to Alabama and picked up a '93 2wd 6.5 diesel xtra cab 8' bed pickup, put it on a steel deck trailer and towed to Vermont-Lake Champlain area. The seller mentioned the dual tanks, and I looked, and there they were. My fuel gauge seems to work in a linear fashion, but one fillup from just above empty only took 28 gallons, another near empty took mid 30's, if I recall. I was on the road for 3+ weeks-4300 miles I filled up alot!

My first fill up was 18.5 miles per gallon, driving around 65 mph, with no AC, and then that dropped to around 15 or so before I loaded up truck & trailer, and loaded up, going 45 50 55, again with no AC plus I was entering the chili Northeast, mileage dropped to the 11 to 13 area. But I drive with a very light foot, I'm very careful to fillup on level ground, and the tank would only take one or two clicks after 1st clickoff, so there was really little room for error. The fuel mileage varied a lot more than I'm used to, and I always check my fuel mileage carefully.

I know I'm wandering off base, but makes for good reading -:))

The Sub had 256k, 1 owner, now has 261k. 6 litre 4x4, and it really struggled up the mountains, but I was very lite on the throttle and used my 4way flashers as neccesary, which was alot!

We had 1' snow a couple days ago, pix taken 11 17 18. I will not be driving this Sub in the winter, I have a 1984 6.2 diesel 4x4 3/4 ton for winter. It just needs to go to the body shop for a tiny bit of rust repair and some paint touch-up. I brought it back from California 11 years ago, and it looks really good, it's just got to keep up on things. I rust-proof my winter driven vehicles extensively, and I've had very very good success keeping the rust at bay

Edited November 18, 2018 by corvairwild

corvairwild · November 18, 2018

I just purchased a 2001 Suburban 2500-4x4 6.0L in Hemet California. I drove it to Alabama and picked up a '93 2wd 6.5 diesel xtra cab 8' bed pickup, put it on a steel deck trailer and towed to Vermont-Lake Champlain area. The seller mentioned the dual tanks, and I looked, and there they were. My fuel gauge seems to work in a linear fashion, but one fillup from just above empty only took 28 gallons, another near empty took mid 30's, if I recall. I was on the road for 3+ weeks-4300 miles I filled up alot!

My first fill up was 18.5 miles per gallon, driving around 65 mph, with no AC, and then that dropped to around 15 or so before I loaded up truck & trailer, and loaded up going 45 50 55, again with no AC plus I was entering the chili Northeast, mileage dropped to the 11 to 13 area. But I drive with a very light foot, I'm very careful to fillup on level ground, and the tank would only take one or two clicks after 11st clickiff, so there was really little room for error. The fuel mileage varied a lot more than I'm used to, and I always check my fuel mileage carefully.

I know I'm wandering off base, but makes for good reading.

The Sub had 256k, 1 owner, now has 261k. 6 litre, and it really struggled up and down the mountains, but I was very lite on the throttle and used my 4way flashers as neccesary.

nickh5413 · February 18, 2020

Do you have a wiring diagram for the rear tank fuel system. My rear fuel tank will not transfer to the front tank on my 2009 Suburban 2500. The level gauge is still reading.

chrispitude · January 13, 2021

On 8/17/2018 at 6:43 PM, superdeeduper said:

so the last post in this thread on 11/19/2014. did you ever get it figured out? (reviving an old post but this is the problem i'm having.) i've got an 08 suburban w/LMM. i'm guessing my secondary tank is not working because my last 2 fill-ups have only taken 24-ish gallons (roughly the size of the primary tank only) AND gas won't run into the filler hole at anything but a painfully slow rate when i'm re-fueling so i'm guessing the secondary tank pump is not activating and the tank is staying full and also preventing normal filling.

Did you ever figure this out? My 2013 Yukon XL with an LML conversion is showing almost exactly the same behavior.