I have not gotten an answer back from GDE and thought someone else might have experienced this. I installed the Eco Tune last week and noticed that as the needle hit close to half a tank it didn't move for a long time. I thought it was busted until it finally moved again. When I hit a quarter of a tank it stayed there for a good while but after shutting the engine off for a short while, I got back in to leave and the tank was on empty and the fuel light was on. It had been at a quarter when I shut it off and I know I do not have a big puddle of fuel on the driveway.

I filled up and topped it up and only was able to put 16 gallons in, however the fuel gauge only showed three quarters full. After half an hour it creeped up to full and then started to go back down aftyer about 50 miles. The fuel gauge did not seem to act this strange before the tune- could it be related? I know GDE is supposed to have some modification which is intended to correct the fuel gauge oddities but this seems odd.

Did you check you battery..make sure connections are tight and clean... Volts after sitting all night it must be higher than 12.5 if less than 12.49 battery should be replaced...Volts while engine is running to check alt. output should be higher than 13.8 13.9 hopefully in the 14..

Well if thats all good then check the ground wire connection at the tank..then you might have to ohm your fuel sender to see if its in spec.

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2005 Jeep Liberty CRD 2.8L 179,xxx mi. 2nd owner 8/2012
Daily Driver, full factory skids/hitch
GDE Hot Tune, GDE Trans Tune, ARP Studs, Timing Belt/Rockers done at 123,730
Weeks Intake, Samco hoses, 2nd gen fuel head, EHM, Fumoto 102, Mobil 1 5W-40 TDT-oil, M1-301, Inline 195 T-stat, GX3123 7V Steel
Jeep = Just Empty Every Pocket

IIRC the more recent, last 4 years or so, GDE tunes minimize but don't eliminate the inaccurate mpg calculation on the EVIC and attempt to make the fuel gauge readings more linear (ex. so 1/2 a tank on the gauge = ca 10 gallons left).

What you describe is an erratic fuel gauge reading similar to what I experienced on my 05 and stoutdog did on his 06 long after getting the GDE tune. Examples - fill up but gauge won't show full but after a while it creeps up to full or gauge drops like a rock from certain positions. At one point we even wondered if the fuel level float in stoutdog's tank had gone bad because the gauge refused to read full.

Best I can say is that in both cases the problem went away once we replaced our rather old but still functional red tops with new batteries. In my case the red top would still crank but noticeably slow in 25F North Florida winter and I can say the odd fuel gauge problem stopped either immediately or nearly so. In stoutdog's case the red top still seemed ok, doesn't get cold in Tempe AZ winter, but given my experience and the age on his battery we decided to give the battery replacement a try. His odd fuel gauge readings did not go away immediately but after a month or 2 and some refills the problem disappeared. I have a Sears P1 and stoutdog has an Interstate Megatron 85.

I have no clue why a battery change would influence odd fuel gauge behavior but it did. Best I can say is if your battery is old replace it with a good group 34 one with 800 or so CCA. If our battery is not old try cleaning the terminals and checking the grounding cables.

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Sold to LOST member my 05 Ltd, GDE Stg II turbo + TCM tune, SunCoast TC w. Transgo kit, Steiger window regulators, Samcos, Fumoto valve, 2nd gen filter head with Lub. Spec. bleeder, Hayden clutch & 11 blade fan, inverted spare, P-1 battery, BF Goodrich Long Trail TAs, Etecno1 glow plugs, timing belt at 50K miles/8 yrs

Battery and alternator are new as of last summer. No starting difficulties that would point me in that direction but I could check the readings. I would hate to run out of fuel so need to sort something out. Any tips on finding the ground wire at the tank?

This is correct but it only applies to the 05. How did you install the tune? If you removed and mailed the ECU you should maybe start by ensuring everything in this area is connected correctly.

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Share your ideas freely at https://www.facebook.com/groups/libertydiesels/

Mine does the exact same thing. I have an 05. Keith told me I neded to cycle the switch after fill up. Did nothing. I'm learning to live with it.

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OME 2790/2948 Rancho all around
JBA strut plates with clevis lift
2 extra rear upper isolators and one extra lower
Front sits 23
Rear sits 22 3/4
265 75 16 Maxxis Big Horn MT
GDE Hot Tune
Bumper trimming up front

Uploaded the modified file via OBD port.

I have a hard time learning to live with snags like this. I am on my second tank since the tune so hopefully this gremlin bugs off.

Really, how complicated is it to make an accurate fuel gauge? Let me guess- it was made by Lucas...

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2006 Limited Edition. GDE- Eco Tune. Crappy floor mats, no spare wheel cover