Chevy and GMC Duramax Diesel Forum banner

1 - 20 of 23 Posts

·
Premium Member
Joined
·
585 Posts
Discussion Starter #1
owners manual says nothing about this system at all. Does it make any difference which tank gets filled first?
From what I have found out, it uses a transfer pump in the rear tank to feed the front tank which feeds the engine. The only quantity sensor is in the front tank and it supposedly uses an algorithm to calculate total quantity.
Anybody have one of these systems on their truck? My previous 4 3500's were all single tank trucks.
Thanks for any guidance
John R Dunn
 

·
Registered
Joined
·
1,151 Posts
First I've heard of dual tanks? What's the owner's manual say the total capacity is?

Maybe there are floats in each tank and the transfer pump keeps them even?
 

·
Registered
Joined
·
6,115 Posts
Cab & Chassis models have dual tanks standard, 23 gallon front, 40 gallon rear.
 

·
Registered
Joined
·
6,276 Posts
Both is standard - and they are also available with just the 23 or just the 40.
 

·
Premium Member
Joined
·
585 Posts
Discussion Starter #5
Well, a little info on the dual tank system for anybodys info.

Front tank is 23.5 gals. and the rear is 40. You will find that the fuel quantity gauge reads both tanks by an algorithm. When mine shows 1/8 remaining, I filled the front first and it took 10.7 gals. The rear took 34 gals. The system uses a transfer pump to move the fuel to the front but will stop transferring when it reaches a certain level to not run the tank/lines dry. I don't think it makes a difference which tank you fill first as long as you don't have the truck running and try to fill the rear first-- it will try to transfer fuel to the front if it is low.
Also, the fuel filter is mounted in front of the REAR tank, not the front like a single tank truck.
 

·
Registered
Joined
·
2 Posts
I have a 2016 Cab Chassis 3500 Crew Cab Duramax with just now 23k for miles.

I just had my first issue with my dual tank set up. I used to fill the front first but it always spit fuel back after 4 or 5 gallons so I just always filled the rear. I filled up yesterday as normal I typically don't shut off the engine when traveling unless I absolutely have. After filling up I drove about 10 miles then the engine threw a code DTC P2636. The check engine light came on, the DTC said low fuel and the gage dropped to Empty.
I called the local dealer as I was out of town traveling home and they were no help, finally called another dealer and he said to just keep the front tank full and I should make it home. So I stopped a couple times and squeezed in some fuel.

Took it to the dealer this morning and I asked about the recall on the fuel transfer that was done in June 18, about 10k miles ago. He said it was done I asked then what went wrong he said it was I did not shut the truck off and fuel the front tank that caused the problem. That does not make any sense to me, what sensor would know that I was fueling other than the gauge, and why would it matter what tank, as I was told that the recall was to by the pump.

Before this truck I had the exact truck except it was a 2006, it was dual tank etc.. I never had any issues with it but a turbo code on a trip to Maine and the dealer replaced it (turbo) around 92K.

Someone enlighten me.
 

·
Premium Member
Joined
·
585 Posts
Discussion Starter #7
I think the second dealer didn't know how the system works. If GM didn't change it up I would think it would be like the ones I have. I don't shut down just to fuel and have had zero problems. I will fill the front first then the rear. If the front is low, and you fill the rear, once the transfer pump senses enough fuel it will start to send it to the front tank because it senses front low and will continue to send it until the front is full. On mine, if I had 1/8 showing on gage I filled front first then rear otherwise I just filled the rear.
Don't understand what went wrong with yours unless the transfer system quit or the gage is off. Post up what you figure out please.
 

·
Registered
Joined
·
39 Posts
Interesting, I’ve found on my 2019 chassis cab that I have to fill the rear first and the front generally doesn’t take as much fuel. I may try to fill the front next time, but generally even near 1/4 tank the front appears to be full.
 

·
Registered
Joined
·
1 Posts
I just got a 2015 HD3500 cab Chassis and while driving it yesterday with the fuel gage showing a quarter of a tank the low fuel light came one and the gage dropped to empty. Also the check engine light came on. I put fuel in the rear tank and then today put fuel in the front tank but was able to get just a little in. I had the code checked and it was the P2636 code which is the was the transfer pump but it must still be working as the front tank still seemed full. Any ideas would be helpful. thanks, Steve
 

·
Registered
Joined
·
220 Posts
same subject ,well sort of , I have a 2019 Chev crew cab 3500 Duramax how big is the fuel tank on it . Thanks Randy
 

·
Registered
Joined
·
6,276 Posts
same subject ,well sort of , I have a 2019 Chev crew cab 3500 Duramax how big is the fuel tank on it . Thanks Randy
2019 3500 pickups have 36 gal tanks.



Because of the factory changeover process, all 2019 3500's were crews
 

·
Premium Member
Joined
·
585 Posts
Discussion Starter #12
Steve,
I was just reading the new GM TECHLINK newsletter. It has an article concerning the 15-19 trucks with dual tanks. Has to do with dirt on top of the rear tank blocking the tank vent fitting. Can make transfer slow etc. Post what you finally find out what is happening.
 

·
Registered
Joined
·
1 Posts
I am new so please forgive my newbie/ness. I have just purchased a 2017 2500hd duramax. The fuel gauge shows I am 1/2 full. It appears I have two fuel tanks as indicated but two small lights at the bottom of the gauge. One is only 1/8th and the other full. My miles says I can go 541miles. Owners manual says the rear tank empties first and then the front. I have only one fuel cap. I went to the station and after 2$ the handle turned off meaning the front tank is full. This has to be for the front tank. How do I fill the rear tank? I would figure these would have a crossover pipe to even them out and fill both tanks at once or a second fuel cap. Can anyone help me figure this out?
 

·
Premium Member
Joined
·
585 Posts
Discussion Starter #14
Do you have the owners manual? All dual tank trucks I've seen have 2 filler ports but those were flatbed equipped. The rear will not empty completely or the lines would have air in them. Is your second tank installed behind the diff between the frame rails where the spare normally goes?
if you have only one gauge how do you know how much is in each tank? What do the lights do?
Sorry for all the questions-- all my dual tank trucks were WT's.
 

·
Registered
Joined
·
6,276 Posts
I am new so please forgive my newbie/ness. I have just purchased a 2017 2500hd duramax. The fuel gauge shows I am 1/2 full. It appears I have two fuel tanks as indicated but . One is only 1/8th and the other full. My miles says I can go 541miles. Owners manual says the rear tank empties first and then the front. I have only one fuel cap. I went to the station and after 2$ the handle turned off meaning the front tank is full. This has to be for the front tank. How do I fill the rear tank? I would figure these would have a crossover pipe to even them out and fill both tanks at once or a second fuel cap. Can anyone help me figure this out?
Factory didn't put dual tanks in a 2500 or 3500 pickups..
They were only in the chassis cab 3500's. (a 40 gallon and a 23 gallon; they can be ordered with either or both)

If the truck is 'factory' it will have a 35 gallon tank (136L).
541 miles for a full tank is possible.

Seems like maybe the full sender is working so the computer has good info, but the gauge dial is not.

Mine is a daily driver that runs mostly rural 2 lane. Regularly run it 600 miles between fills.

I don't know what you mean about 'two small lights at the bottom of the gauge'.
 

·
Registered
Joined
·
1 Posts
I have a 2016 Cab Chassis 3500 Crew Cab Duramax with just now 23k for miles.

I just had my first issue with my dual tank set up. I used to fill the front first but it always spit fuel back after 4 or 5 gallons so I just always filled the rear. I filled up yesterday as normal I typically don't shut off the engine when traveling unless I absolutely have. After filling up I drove about 10 miles then the engine threw a code DTC P2636. The check engine light came on, the DTC said low fuel and the gage dropped to Empty.
I called the local dealer as I was out of town traveling home and they were no help, finally called another dealer and he said to just keep the front tank full and I should make it home. So I stopped a couple times and squeezed in some fuel.

Took it to the dealer this morning and I asked about the recall on the fuel transfer that was done in June 18, about 10k miles ago. He said it was done I asked then what went wrong he said it was I did not shut the truck off and fuel the front tank that caused the problem. That does not make any sense to me, what sensor would know that I was fueling other than the gauge, and why would it matter what tank, as I was told that the recall was to by the pump.

Before this truck I had the exact truck except it was a 2006, it was dual tank etc.. I never had any issues with it but a turbo code on a trip to Maine and the dealer replaced it (turbo) around 92K.

Someone enlighten me.
The work truck I'm issued is a 2015 3500 chassis cab with the dual tanks. I had the same problem twice with the fuel guage dropping to E and the truck only pulling from the front tank. According to the in-house mechanic, the reason it happened is there's a sensor or gauge in between the 2 tanks on the exterior that has a sort of gaurd or something on it. It caught a bunch of mud and had to be cleaned out for it to work properly again. Might be your problem depending on what terrain you deal with.
 

·
Registered
Joined
·
721 Posts
So can anyone tell me if the factory 40 gallon rear tank found on C/C trucks will fit in the spare tire spot of a regular C/K3500 pickup? I'm not concerned with all the automatic transfer apparatus. If it would fit, I'd just plumb up a simple switched transfer pump that works. Thank you.
 

·
Premium Member
Joined
·
585 Posts
Discussion Starter #18
I don't see why not. The frame rails etc. are all in the same spots. The top of the tank is slightly below the rail tops so unless the bed sticks down it should fit. Take a look at gm upfitters and it has a few bulletins on deleting the rear tank and which lines go where. You should be able to use the intank pump and some of the lines to do what you want. Maybe you can find one in a salvage yard for cheap. Can't imagine there is a big demand for rear tanks. Post up what you do with this please.
 
  • Like
Reactions: blythkd1

·
Registered
Joined
·
721 Posts
Yeah I was thinking the salvage yard deal too but would like to be reasonable sure it would fit before buying one. I bought a 40 gallon aft tank for a Ford from salvage a few years ago and it was $300. Evidently they've heard that gas tanks aren't cheap.

I don't care much about having a spare under the back of a dually. I figure in a pinch, I'm running a couple of spares on the back at all times anyway. And it's not like I ever need one anyway. Last time I needed one, I had a bad valve stem:)
 

·
Registered
Joined
·
892 Posts
IIRC the frame rails on C&C are not the same width as bed equipped trucks.
 
1 - 20 of 23 Posts
Top