Duramax Diesels Forum Truck of the Week
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Old 04-23-2019, 10:02 AM
DreksDmax DreksDmax is offline
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Default Bad fuel sending unit?

Hey guys just bought an 08 LMM from local Chevy dealer. Truck has 80k miles, one owner. Filled up last night for first time, had about an 1:8th of a tank, filled up with 15 gal, Iím assuming bad sending unit or gauge? Seems to be a common issue with these models

Thanks in advance
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Old 04-23-2019, 11:29 AM
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Was the low fuel light on?
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Old 04-23-2019, 01:23 PM
DreksDmax DreksDmax is offline
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Was the low fuel light on?
No it was not, but range said like 57 miles
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Old 04-23-2019, 01:49 PM
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LMM's are very bad about the fuel gauge being way off. I have taken the sending unit out and bent the float arm to get it to read where you want it like 3 or 4 gallons left and then the low light comes on

I think you can adj it with EFI live as well not 100% sure on that
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Old 04-23-2019, 02:02 PM
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GM has it like this from the factory. Light comes on with something like 10 gallons still in the tank. Supposedly to reduce people from running out while towing

You can make some adjustments with EFILive but there is a section of the table that is low resolution so you can't get it where it should be without bending the arm some to make it operate in the high resolution section of the table

There is also the possibility of yours being bad too
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Old 04-23-2019, 02:29 PM
DreksDmax DreksDmax is offline
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Quote:
Originally Posted by 2004LB7 View Post
GM has it like this from the factory. Light comes on with something like 10 gallons still in the tank. Supposedly to reduce people from running out while towing

You can make some adjustments with EFILive but there is a section of the table that is low resolution so you can't get it where it should be without bending the arm some to make it operate in the high resolution section of the table

There is also the possibility of yours being bad too

Interesting. My pops also has an 08, he never lets his go below 1/4 tank and says it takes around 17-18gal at that point. So if my gas light comes on I should have around 10 gal left and 100-120 miles plus left? So my range is not accurate either. At fill up last night the range said 270 miles. Is that about right?
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Old 04-23-2019, 03:32 PM
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I've never really paid to much attention to range but I know my gallons used is never off by more then a gallon when I fill up so that is what I normally look at.

I installed a different sending unit then factory and scaled the table to turn the light on at about 4 gallons left. I almost always fill up with the light on and I've fit 34 gallons in the tank many times

Before I would only get 22-24 in with the light on. But I ran out twice trying to estaminet how much left before stopping to fill up
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Old 04-23-2019, 03:36 PM
DreksDmax DreksDmax is offline
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Quote:
Originally Posted by 2004LB7 View Post
I've never really paid to much attention to range but I know my gallons used is never off by more then a gallon when I fill up so that is what I normally look at.

I installed a different sending unit then factory and scaled the table to turn the light on at about 4 gallons left. I almost always fill up with the light on and I've fit 34 gallons in the tank many times

Before I would only get 22-24 in with the light on. But I ran out twice trying to estaminet how much left before stopping to fill up
Guess this time Iíll see how low it goes before my light comes on
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Old 04-24-2019, 06:55 AM
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On my 08 when the fuel sending unit went out it started going crazy. It would read full then a few hrs later it would read 1/2 then maybe 3/4 an hr later. Now my trucks run all day so itís easy for me to notices these things. Might be harder if your not in your truck all day.


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Old 04-24-2019, 06:50 PM
Ron Nielson Ron Nielson is offline
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Talk to the dealer and see if they will fix this. You hav nothng to loose by asking; and if you don't ask, it's coming OUT OF YOUR POCKET
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Old 04-24-2019, 08:07 PM
DreksDmax DreksDmax is offline
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Quote:
Originally Posted by Ron Nielson View Post
Talk to the dealer and see if they will fix this. You hav nothng to loose by asking; and if you don't ask, it's coming OUT OF YOUR POCKET
I asked. Nope truck was sold as is
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Old 04-24-2019, 11:08 PM
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Normal. My 06 says empty at 270 miles or about 19 gallons.
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