Duramax Diesels Forum Truck of the Week
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Old 05-04-2018, 07:55 AM
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Default Fuel gauge adjustment

I have a customer with an lbz. He has owned the truck since new and has always had fuel gauge issues. Everything works and reads but when the low fuel light comes on the truck still has about 14 gallons of fuel in the tank. Is there an adjustment I can make with efi-live to make it a little more accurate?

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Old 05-04-2018, 08:01 AM
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I’ve seen this a couple times.. adjusted the float rod on an lmm while doing a sump install to correct it some. It did the same thing, like the float wasn’t going all the way to the bottom of the tank
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Old 05-04-2018, 08:04 AM
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to do it in EFI Live, it will take a long time. basically drain tank, set gauge at E, then add a gal, make adjustment and keep going till its full.

does he have a 26 gal short bed OS in place of his 34 gal long bed OS, assuming its a long bed?

otherwise its like Corbin said and something to do with the float.
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Old 05-04-2018, 08:04 AM
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Getting a titan tank to read correct seems damn near impossible
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Old 05-04-2018, 08:34 AM
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Mines the same way, as soon as it hits E I fill up and it only takes 12-13 gallon, it’s annoying as ****. I don’t even know how to correct it if someone else is doing the tuning.
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Old 05-04-2018, 08:47 AM
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As James tuched on, you log your fuel level voltage with EfiLive while filling up. I just wrote down what the readings where every half gallon added.

Then put the figures in the the tune. It should be close with just that but the top and bottom may need tweaking. You will need to run it low again until the light comes on and see how many gallons you can get back in.

One issue though is that the table that holds the fuel level figures has a large jump right where you need to make the adjustments so you are kind of stuck.

You can bend your float rod to keep the readings within the area that has the full scaling then do the logging and tune adjustments.

I ended up just installing an aftermarket float with the right ohm reading and scaled that. Light comes on with 3-4 gallons left. I've been able to get 34 gallons in without running out or stalling

As you can see it can take some work and a lot of time to get it right
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Old 05-04-2018, 08:58 AM
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Quote:
Originally Posted by Chevy1925 View Post
to do it in EFI Live, it will take a long time. basically drain tank, set gauge at E, then add a gal, make adjustment and keep going till its full.

does he have a 26 gal short bed OS in place of his 34 gal long bed OS, assuming its a long bed?

otherwise its like Corbin said and something to do with the float.
It is a short bed with 26 gallon tank. The o.s. completely factory and set up as a 26 gallon tank. Might just bend the float rod like Corbin said.

Funny that a titan tank was mentioned. He wants me to price installing one of those for him.

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Old 05-04-2018, 09:03 AM
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Quote:
Originally Posted by 02greysixer View Post
It is a short bed with 26 gallon tank. The o.s. completely factory and set up as a 26 gallon tank. Might just bend the float rod like Corbin said.

Funny that a titan tank was mentioned. He wants me to price installing one of those for him.

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tell him that gauge reading will just get waaaaaay worse lol
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02 LL7 2500HD CC/LB dmax/alli "The Limo"

BIG THANKS TO: Mike L, Steve, Trent, Guy, Dan, Ruben, Josh H, Scott, Brian and everyone else who has put a hand in to help me.

best time to date: 12.39

motor died/bent rods = 3/11/11
back from the dead 7:04pm 4/9/2012

Limo is back in the garage, now driving a built chevy tracker
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Old 05-04-2018, 09:03 AM
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Quote:
Originally Posted by 02greysixer View Post
It is a short bed with 26 gallon tank. The o.s. completely factory and set up as a 26 gallon tank. Might just bend the float rod like Corbin said.

Funny that a titan tank was mentioned. He wants me to price installing one of those for him.

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They are great tanks and if you want the added range they are perfect. Iíve just not had luck scaling the sensor to read correct. Which it shouldnít need re scaled in theroy
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Old 05-04-2018, 01:07 PM
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Mine didn’t used to be as bad, I’m wondering if it’s from always filling up from 1/4-1/2 a tank? I always had my fuel cell so I never let mine get anywhere close to E.
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Old 05-04-2018, 01:41 PM
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Quote:
Originally Posted by clrussell View Post
They are great tanks and if you want the added range they are perfect. I’ve just not had luck scaling the sensor to read correct. Which it shouldn’t need re scaled in theroy
Yes its great to have but reading them is a pain. When Russ installed my DSP-5 with the LBZ transplant, it took him a couple of tries to get it close enough. Right now when it reads half a tank, you'll actually put in 33-35 gallons. At 3/8 of a tank, you'll put in 41 gallons and then the gauge drops really quick. When the light comes on, I usually can put in between 45-47 gallons. The problem is, when you top your tank off and you reach 100 miles the gauge drops to zero, low fuel light comes on and the check engine light also. It all resets itself after a few starts or about 20 miles.
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Old 06-06-2018, 03:49 AM
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Little update to this. He brought me the truck yesterday after driving 50 miles past "0 miles to empty". I dropped the tank and still had about 10 gallons in it. The sending unit pick up assembly had some rust on it so I recommended replacement. I bought an oreilly one and on a hunch I put it in the factory tank without removing any fuel. Gauge on the dash now showed between 1/8 and 1/4. So I carried on with the 52 gallon titan install. Installed dry, key on with no fuel in it and light was on with no gauge movement. 5 gallons in and light still on but gauge moved slightly. 5 more gallons and I had 1/8 tank. 5 more and a little over 1/4. 5 more just under 1/2. 25 gallons got right at 1/2 tank.

Bottom line, parts store level indicator seems to have fixed his issue.

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Old 06-06-2018, 04:37 AM
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The sensor gets that white gel on it from water in fuel, remove it and clean it with electrical cleaner and reinstall. I did clean up board a little with a fine brush, mine worked perfect after that...
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Old 06-06-2018, 09:09 AM
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I would just replace the sending unit. They go out bad all the time on the gassers too, so itís not because of build up.


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Old 06-06-2018, 02:16 PM
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Yeah he replaced the sender already years ago with a new gm one. Maybe in 08 or 09 he said. No change. Still read empty with 8 to 10 gallons in the tank. So this is sender number 3. Normally I like to use o.e.m. ones but figured what the hell, factory one didn't change anything might as well try an aftermarket.

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