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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ, LMM & LML engine specific topics.

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Old 05-09-2010, 07:18 PM
SDakDmax SDakDmax is offline
Join Date: Mar 2004
Location: South Dakota
Posts: 40
Default fuel gauge problem

I have a 2001 extended cab short box. When the tank is full the gauge will show full, then it will go to empty and the low fuel light will come on. After about 10 seconds it will go back to full. It will do this off and on until the tank is close to 1/2. then all is well. Does this sound like the sending unit? If so what is the best way to get to it. drop the tank or lift the box? I noticed in another thread someone said to put a good dose of sea foam? I usually don't have much luck with anything like that working, seems like new parts is what it takes. Thanks for any advise that I can get.
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Old 05-10-2010, 05:59 AM
cowboywildbill's Avatar
cowboywildbill cowboywildbill is offline
Join Date: Oct 2002
Location: USA
Posts: 1,203

Sounds like some gunk on the sending unit. Or it has a dead spot on it. They are basically just a reostat/potentiometer, I'm sure I screwed the spelling on that!. At least they used to be. It could be a bad guage also. You can ground the sending unit wire and if the guage goes to full and stays, then it is most likely the sending unit.
It is likely mounted in the top of the tank and you would have to drop it down and maybe take it out to get at it. Just make sure it's near empty if you do drop it. Makes it lot's easier and safer. I'm sure one of the techs will know. Good luck.
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Old 05-12-2010, 03:30 PM
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More Power More Power is offline
Join Date: Feb 2000
Location: Big Sky Country
Posts: 10,205

The following forum thread has some good info that is useful for troubleshooting a fuel tank sender.

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Old 05-20-2010, 08:24 PM
SDakDmax SDakDmax is offline
Join Date: Mar 2004
Location: South Dakota
Posts: 40
Default fuel gauge problem

thanks for the reply Jim, Always glad I'm a member to The Diesel Page. Best money I spend. I'll get my ohm meter out and check this. I did find this site for sending units. or search tri-starr sending unit. i think it was abut $89.00 Thanks again ,,,,
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