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2500 Fuel System Question

Wingo said:
The rear tank is pretty easy. You'll have to drop the tire, remove the spare tire bracket, then the two tank strap bolts. When disconnecting the fuel filler hoses, I found it easier to remove them from the big tank side, and then just unbolt the fuel filler neck and ground strap from the filler door, it's only three small bolts- easier to get to. Then of course unhook your fuel pump wires and fuel lines when you can lower it enough. Also, while you are at it. I recommend removing the anti siphon flapper valve from the plastic T fitting on top of the little tank, it's the one both filler hoses attach to, you'll see it wobbling in there. It's easy to over tighten those hose clamps and deform it. Do that and filling that thing up will be a nightmare. Ask how I know, had to drop the tank a bit to get that thing out again. I slid the whole flapper assembly out, removed the metal pin and flapper- it's about the size of a quarter, and put the rest back in the T fitting- I felt the T was kinda flimsy without it.

I'm not sure about the gauge reading. There is a float and sender on that pump, I don't know if it is only to shut the pump off when it's empty, or if the truck uses that reading to calculate remaining fuel. I really have no idea.
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I can provide some first hand experience with how the fuel gauge in the dash reads and how large each tank is. I recently bought an 04’ 2500 and the neck of the rear fuel tank was cracked. My first fuel up attempt lead to gasoline just dumping on the ground instead of going into the truck. I ended up cutting the hose leading to that tank and plugging it off so I could at least put gas in the truck. So now I just have the main/front tank operational only.

When I fill the truck up all the way the fuel gauge in the dash only reads 3/4. To verify the main tank was actually filling 100% I fueled up until gas overflowed out of the filler neck. The truck definitely calculates how much fuel is in each tank and then displays a single reading on the dash. Furthermore, I have HPtuners and licensed the truck. The PCM file shows the main tank is 25 gallons and the rear tank is 13 (38 total). Additionally, 25 is 65% of 38 which closely matched my dash read out. Even further I “tuned out”/deleted my rear fuel tank in the PCM file to see if I could get my fuel gauge to read correctly for only using the main tank. I was successful and now when I gas up I have an accurate fuel reading. I usually fill up at a 1/2 tank and I routinely put in 12-13 gallons.

Summary: fuel gauge takes a reading from both tanks and a single reading is calculated by the PCM. The main tank appears to be 25 gallons and rear appears to be 13 gallons.

I will be attempting to replace my fuel lines and the rear tank in the next few days. I’ve found full replacement fuel line kits for 02-03 trucks but not 04 and newer. Does anyone know if the 02-03 kit would work? I reached out to fine lines / sstubes.com and they didn’t think their 02-03 kit would work on an 04 because the evap and emissions systems allegedly were changed in 04. Any insight would be helpful. Thanks
 
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8100Avy said:
I can provide some first hand experience with how the fuel gauge in the dash reads and how large each tank is. I recently bought an 04’ 2500 and the neck of the rear fuel tank was cracked. My first fuel up attempt lead to gasoline just dumping on the ground instead of going into the truck. I ended up cutting the hose leading to that tank and plugging it off so I could at least put gas in the truck. So now I just have the main/front tank operational only.

When I fill the truck up all the way the fuel gauge in the dash only reads 3/4. To verify the main tank was actually filling 100% I fueled up until gas overflowed out of the filler neck. The truck definitely calculates how much fuel is in each tank and then displays a single reading on the dash. Furthermore, I have HPtuners and licensed the truck. The PCM file shows the main tank is 25 gallons and the rear tank is 13 (38 total). Additionally, 25 is 65% of 38 which closely matched my dash read out. Even further I “tuned out”/deleted my rear fuel tank in the PCM file to see if I could get my fuel gauge to read correctly for only using the main tank. I was successful and now when I gas up I have an accurate fuel reading. I usually fill up at a 1/2 tank and I routinely put in 12-13 gallons.

Summary: fuel gauge takes a reading from both tanks and a single reading is calculated by the PCM. The main tank appears to be 25 gallons and rear appears to be 13 gallons.

I will be attempting to replace my fuel lines and the rear tank in the next few days. I’ve found full replacement fuel line kits for 02-03 trucks but not 04 and newer. Does anyone know if the 02-03 kit would work? I reached out to fine lines / sstubes.com and they didn’t think their 02-03 kit would work on an 04 because the evap and emissions systems allegedly were changed in 04. Any insight would be helpful. Thanks
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So if I can get someone with HP tuner to delete the rear tank I shouldn't have a problem? It should read right?
 
8100Avy said:
I can provide some first hand experience with how the fuel gauge in the dash reads and how large each tank is. I recently bought an 04’ 2500 and the neck of the rear fuel tank was cracked. My first fuel up attempt lead to gasoline just dumping on the ground instead of going into the truck. I ended up cutting the hose leading to that tank and plugging it off so I could at least put gas in the truck. So now I just have the main/front tank operational only.

When I fill the truck up all the way the fuel gauge in the dash only reads 3/4. To verify the main tank was actually filling 100% I fueled up until gas overflowed out of the filler neck. The truck definitely calculates how much fuel is in each tank and then displays a single reading on the dash. Furthermore, I have HPtuners and licensed the truck. The PCM file shows the main tank is 25 gallons and the rear tank is 13 (38 total). Additionally, 25 is 65% of 38 which closely matched my dash read out. Even further I “tuned out”/deleted my rear fuel tank in the PCM file to see if I could get my fuel gauge to read correctly for only using the main tank. I was successful and now when I gas up I have an accurate fuel reading. I usually fill up at a 1/2 tank and I routinely put in 12-13 gallons.

Summary: fuel gauge takes a reading from both tanks and a single reading is calculated by the PCM. The main tank appears to be 25 gallons and rear appears to be 13 gallons.

I will be attempting to replace my fuel lines and the rear tank in the next few days. I’ve found full replacement fuel line kits for 02-03 trucks but not 04 and newer. Does anyone know if the 02-03 kit would work? I reached out to fine lines / sstubes.com and they didn’t think their 02-03 kit would work on an 04 because the evap and emissions systems allegedly were changed in 04. Any insight would be helpful. Thanks
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2004 has a return less fuel system. MAY be the same fuel lines but just missing the return line.

I need to dig into mine. When I fill the tank I get a gas smell until I use up enough gas so it doesn't. It only happens when I have a full tank.
 
Sstevieboy0208 said:
So if I can get someone with HP tuner to delete the rear tank I shouldn't have a problem? It should read right?
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If you have a similar issue as me and you’re not using the rear tank, HPtuners can get your dash to read just the main tank correctly. It was a simple fix and you don’t need to be a tuner to do it. Instead of paying a couple hundred bucks for someone to do it you could purchase an HPtuners device and license the truck yourself if you’re up for it. HPtuners is a good scan tool to diagnose any future problems, can delete/erase nonsense check engine lights, etc. I also use mine for any used cars the family purchases so I can see the DTC history of the car. Just something to consider. I’d be willing to assist you if needed.

To delete the rear tank with HPtuners….Under the main fuel tab, you can find values for both tanks as well as total combined volume. I changed the rear tank volume to zero in all fields and changed the combined volume to the same value as the main tank. I did not modify the main tank values. The truck out no longer accounts for the rear tank and operates as if the main tank is the only fuel tank. It took me a few mouse clicks and 5 minutes tops.
 
redheadedrod said:
2004 has a return less fuel system. MAY be the same fuel lines but just missing the return line.

I need to dig into mine. When I fill the tank I get a gas smell until I use up enough gas so it doesn't. It only happens when I have a full tank.
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Appreciate the insight. I’ll try to call some other businesses today and see if I can find a solution. Good luck with your project.
 
8100Avy said:
If you have a similar issue as me and you’re not using the rear tank, HPtuners can get your dash to read just the main tank correctly. It was a simple fix and you don’t need to be a tuner to do it. Instead of paying a couple hundred bucks for someone to do it you could purchase an HPtuners device and license the truck yourself if you’re up for it. HPtuners is a good scan tool to diagnose any future problems, can delete/erase nonsense check engine lights, etc. I also use mine for any used cars the family purchases so I can see the DTC history of the car. Just something to consider. I’d be willing to assist you if needed.

To delete the rear tank with HPtuners….Under the main fuel tab, you can find values for both tanks as well as total combined volume. I changed the rear tank volume to zero in all fields and changed the combined volume to the same value as the main tank. I did not modify the main tank values. The truck out no longer accounts for the rear tank and operates as if the main tank is the only fuel tank. It took me a few mouse clicks and 5 minutes tops.
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My issue is the rear pump not reading right and throwing a code for it. Where are you located
 
Why delete it you can buy a new pump for around $60, it comes with a new fuel level sender..
Just drop the tank and replace it... What am I missing? No skills to do it?
 
Randy said:
Why delete it you can buy a new pump for around $60, it comes with a new fuel level sender..
Just drop the tank and replace it... What am I missing? No skills to do it?
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Where did you find it for 60 brother ? I can actually do it myself
 
ebay.. you'll have to verify the PN.. If I was closer, I'd help you..

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Reno Nevada...
 
Randy said:
Reno Nevada...
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A little far for me. Anyway I looked up the code I'm getting and found a service bulletin about that code with a hose that balances both tanks and looking under my truck found a skinny hose coming from the rear tank just hanging there. So tomorrow I'm going to look into it and will keep you guys posted.
 
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