# 04 3500 Dmax, Dual Fuel tank Problems???



## Mike S (Feb 11, 2007)

The fuel gauge quites working and when it does it loses prime. I installed a new lift pump and it didnt solve anything. Help!!! The gauge will stop working and then start working again and when it starts working again it will also lose prime. It codes when it does it! Tomorrow I will get it scaned. Anyone have this problem?!!!!!


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## Mike S (Feb 11, 2007)

Never mind took a wild guess and bought a new float for the back tank and that seemed to work.


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## blowerman (Dec 24, 2007)

I hope you don't fuel up with the truck running... Non stop problems with our older dual tank duramax trucks.


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## Mike S (Feb 11, 2007)

Never mind it did it again!!!!!!!!!! Still have same problem! HELP!


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## B&B (Nov 4, 2006)

Mike S;644053 said:


> Never mind took a wild guess and bought a new float for the back tank and that seemed to work.





Mike S;646493 said:


> Never mind it did it again!!!!!!!!!! Still have same problem! HELP!


You changed the wrong sending unit Mike. It needs the front one.


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## Riccas (Dec 21, 2006)

Duramax engine doesn't have a liftpump to begin with... its got CP3s which is a motor driven suction pump, not a lift pump, so you might want to start in the tank if theres a fuel sending issue. Also what config do you have that you have dual fuel tanks?? I've owned every year duramax from 01-07 and none of them have dual tanks on my 3500's regarless of cab config or bed option.


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## Riccas (Dec 21, 2006)

Duramax tanks are suposed to operate on weight sending... not float sending... interested to know what kind of tanks are on there...


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## blowerman (Dec 24, 2007)

02, 3500 one ton dump has dual tanks. The dealer says the back tank fills the front and then the front goes to the engine? Correct me if that's wrong.


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## bowtie_guy (Jan 1, 2004)

blowerman;646986 said:


> 02, 3500 one ton dump has dual tanks. The dealer says the back tank fills the front and then the front goes to the engine? Correct me if that's wrong.


Correct!! 

Cab and Chassis trucks come with dual tanks.


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## B&B (Nov 4, 2006)

blowerman;646986 said:


> The dealer says the back tank fills the front and then the front goes to the engine? Correct me if that's wrong.


Correct, the PCM reads the fuel level on BOTH tanks and by way of the frame mounted transfer pump (what I think Mike was referring to as a "lift pump") it pumps fuel from the rear tank to the front one as its used...as the engine only pulls fuel from the front one. If the PCM gets an erroneous reading (or none at all) from either tank it can cause all sorts of strange issues.


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## Mike S (Feb 11, 2007)

B&B what do you recomend I try next?


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## B&B (Nov 4, 2006)

Replace the front sender assembly Mike. 

They're usually the ones that die most often anyway.


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## Mike S (Feb 11, 2007)

Thank you!!!!


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## Mike S (Feb 11, 2007)

Ordered the front sending unit and will have it in by noon tomorrow! Lets hope for the best!


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## sjosephlawncare (Jan 17, 2008)

My 04 C&C did that when it was new, Jack Maxtons replaced the front sender(under warenty) and it never did it again. It was very fustrating when it did that, left me stranded a couple of times, cause I didn't know what to do.


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## Mike S (Feb 11, 2007)

Awsome! Thats funny Maxton didnt even want to look at it! Oh well! That makes me feel better that the sender could probably fix my problem! Thank you! Who's the chick in the avatar?!?LOL!


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## sjosephlawncare (Jan 17, 2008)

Maxton is the only place I trust anymore, that's funny. They have mixed reviews I guess. some hate em, some love em- oh well. That's beth o., howard sterns new wife.


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## Mike S (Feb 11, 2007)

Wow she hot! I bought my 04 2500hd from them and they didnt treat me bad but they didnt fix the over heating problem that the truck had with the meyer that I bought from them. The wrong fan clutch was on it! Oh well! Maxton was not bad on thier selection but I think I like Byers selection better. My duramax I have now was a repo that had 40000 miles on it and was agreat deal! I think im done buying new trucks for a while unless I see a red or blue 3500 Dmax 4x4 SRW utility body truck!


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## Mike S (Feb 11, 2007)

Problem fixed for now!! Front sender! Thanks!


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## B&B (Nov 4, 2006)

Congrats Mike...and your welcome. :waving:


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## Mike S (Feb 11, 2007)

Well the problem came back!!!!! So I gave up and took it to a dealer and they cant figure out what is wrong either!!!!!!! This very frustrating! Thier diesel mechanic was up to the challenge and was very coffident that he could fix it without any problems but know he is not so sure! It funny but it is not. They can not find any thing really wrong. B&B what do you think? Any other ideas I could throw at them?


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## B&B (Nov 4, 2006)

What were the original codes it set Mike? Never had one that changing the front sender DIDN'T fix it.


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## Mike S (Feb 11, 2007)

The codes that came up where only codes that come up that are related to loosing prime. There was one code for the back tank senor but not any more snice it was replaced. Could it be the primer pump or the pirmer pump housing? Thank you B&B!!!


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## ticki2 (Jan 10, 2006)

PO of my '02 had a similar problem . According to the paper work it was a combination of a dirty fuel filter and a bad transfer pump . This also through a code for fuel level sensor 2 but turned out ok after first 2 were fixed. Have heard a some having similar problem when not filling front tank first but have no experience personally . Good luck


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## Mike S (Feb 11, 2007)

The dealer has given up for now!!!! They have talked to gm and they just cant figure it out. They have tried everything I have not and nothing. I asked them about the fass fuel system and they said that might be a good idea. I should have that in and installed on monday. Wish me luck!


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## lunatic81 (Sep 24, 2008)

I had a very similar problem. Only difference is that mine never lost prime. If I parked on a hill, etc the gauge would quit working. The truck had the problem since 06. Last month I took it back in and they fixed it for good. Looking at my paper work it says "Replaced the rear fuel tank with a redesigned tank per tech bulletin #PIT3630E. Reprogrammed the engine control module with updated software calibrations per tech bulletin #PIT4150. Replaced the fuel transfer pump that was mechanically inoperative"

It took the local dealer about 3 days to do all this. I'm sure most of it was waiting for parts. I don't know if this truck is under warranty, but mine had expired. I argued with the service manager about it since they never had a permanent fix for it. I used to take it in once a month or more to get the low fuel light reset and turned off. It's annoying as hell, luckily I keep a fuel tank on back for those oops moments.

Hope this helps.


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## Mike S (Feb 11, 2007)

It is fixed!!!!!!!!!!!!!!!!! Short in a harness!!!


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## Surfside (Oct 10, 2005)

Too many times this is a problem here also. I've been to the dealer atleast 13 time to have the code reset!! They mentioned that there is a vent to install on the fuel line , at my cost, so I havent done it. Parking your truck on a up-slope I was told doesnt help the problem any. It seem like it happens when I fill the rear tank mostly in winter. Any suggestions?


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## lunatic81 (Sep 24, 2008)

Surfside;682654 said:


> Too many times this is a problem here also. I've been to the dealer atleast 13 time to have the code reset!! They mentioned that there is a vent to install on the fuel line , at my cost, so I havent done it. Parking your truck on a up-slope I was told doesnt help the problem any. It seem like it happens when I fill the rear tank mostly in winter. Any suggestions?


Everything you described is exactly what my problems were. I hope you're filling the front tank first, but even then you can still have problems. Tell you're dealer about the things they fixed on my truck, or to look at the service bulletins in my post.


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